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general description the max1233/max1234 are complete pda controllers in 5mm 5mm, 28-pin qfn and tqfn packages. they fea- ture a 12-bit analog-to-digital converter (adc), low on- resistance switches for driving resistive touch screens, an internal +1.0v/+2.5v or external reference, 2? accu- rate, on-chip temperature sensor, direct +6v battery mon- itor, keypad controller, 8-bit digital-to-analog converter (dac), and a synchronous serial interface. each of the keypad controllers?eight row and column inputs can be reconfigured as general-purpose parallel i/o pins (gpio). all analog inputs are fully esd protected, eliminating the need for external transzorb devices. the max1233/max1234 offer programmable resolution and sampling rates. interrupts from the devices alert the host processor when data is ready, when the screen is touched, or a key press is detected. software- configurable scan control and internal timers give the user flexibility without burdening the host processor. these devices consume only 260? at the maximum sampling rate of 50ksps. supply current falls to below 50? for sampling rates of 10ksps. the max1233/max1234 are guaranteed over the -40 c to +85 c temperature range. applications personal digital assistants pagers touch-screen monitors cellular phones mp3 players portable instruments point-of-sale terminals features ? esd-protected analog inputs 15kv iec 1000-4-2 air-gap discharge 8kv iec 1000-4-2 contact discharge ? single-supply operation +2.7v to +3.6v (max1233) +4.75v to +5.25v (max1234) ? 4-wire touch-screen interface ? internal +1.0v/+2.5v reference or external reference (+1.0v to av dd ) ? spi /qspi /microwire -compatible 10mhz serial interface ? 12-bit, 50ksps adc measures resistive touch-screen position and pressure two auxiliary analog inputs two battery voltages (0.5v to 6v) on-chip temperature ? 8-bit dac for lcd bias control ? 4 4 keypad programmable controller offers up to eight gpio pins ? automatic detection of screen touch, key press, and end of conversion ? programmable 8-, 10-, 12-bit resolution ? programmable conversion rates ? autoshutdown between conversions ? low power 260? at 50ksps 50? at 10ksps 6? at 1ksps 0.3? shutdown current ? 28-pin 5mm 5mm qfn and tqfn packages max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ________________________________________________________________ maxim integrated products 1 28 27 26 25 24 23 22 sclk cs din dout penirq 8 9 10 11 12 13 14 *bat1 *bat2 *aux1 *aux2 ref dacout r4 15 16 17 18 19 20 21 r3 *pin includes 8kv/15kv esd protection. r2 r1 c1 c2 c3 c4 7 6 5 4 3 2 1 gnd *y- *x- *y+ *x+ av dd dv dd max1233 max1234 qfn/tqfn top view keyirq busy pin configuration ordering information 19-2512; rev 4; 3/08 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available part temp range pin-package max1233 egi -40? to +85? 28 qfn (5mm x 5mm) max1233eti -40? to +85? 28 tqfn (5mm x 5mm) max1234 egi -40? to +85? 28 qfn (5mm x 5mm) max1234eti -40? to +85? 28 tqfn (5mm x 5mm) transzorb is a trademark of general semiconductor industries, inc. spi and qspi are trademarks of motorola, inc. microwire is a trademark of national semiconductor corp. autoshutdown is a trademark of maxim integrated products, inc.
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (dv dd = av dd = +2.7v to +3.6v (max1233), dv dd = av dd = +4.75v to +5.25v (max1234), external reference v ref = 2.5v (max1233), v ref = 4.096v (max1234); f sclk = 10mhz, f sample = 50ksps, 12-bit mode, 0.1? capacitor at ref, t a = -40 c to +85?, unless otherwise noted. typical values are at t a = +25?.) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. av dd to gnd............................................................-0.3v to +6v dv dd to av dd .......................................................-0.3v to +0.3v digital inputs/outputs to gnd .................-0.3v to (dv dd + 0.3v) x+, y+, x-, y-, aux1, aux2, and ref to gnd ..................................-0.3v to (av dd + 0.3v) bat1, bat2 to gnd .................................................-0.3v to +6v maximum esd per iec 1000-4-2 (per mil std-883 hbm) x+, x-, y+, y-, aux1, aux2, bat1, bat2...................... 15kv all other pins..................................................................... 2.5kv maximum current into any pin............................................50ma continuous power dissipation (t a = +70 c) 28-pin qfn (derate 28.5mw/ c above +70 c) .................2w 28-pin tqfn (derate 28.5mw/ c above +70 c) ...............2w operating temperature range ...........................-40 c to +85 c storage temperature range .............................-60 c to +150 c lead temperature (soldering, 10s) .................................+300 c parameter symbol conditions min typ max units analog-to-digital converter dc accuracy (note 1) resolution software-programmable 8/10/12 bit 12 bits no missing codes 11 bits 12-bit mode 0.8 2 relative accuracy (note 2) inl 10-bit and 8-bit modes 0.5 lsb 12-bit mode 0.8 2 differential nonlinearity dnl 10-bit and 8-bit modes 0.5 lsb 12-bit mode 0.5 4 offset error 10-bit and 8-bit modes 0.5 lsb 12-bit mode 0.5 4 10-bit mode 0.5 gain error (note 3) 8-bit mode 0.5 lsb 12-bit mode 2 total unadjusted error tue 10-bit and 8-bit modes 1 lsb offset temperature coefficient 0.4 ppm/ c gain temperature coefficient 0.4 ppm/ c channel-to-channel offset 0.1 lsb channel-to-channel gain matching 0.1 lsb noise including internal v ref 50 ? rms max1233 av dd = dv dd = +2.7v to +3.6v 0.4 power-supply rejection psr full-scale input max1234 av dd = dv dd = +5v 5% 0.3 mv dynamic specifications (1khz sine wave, v in = 2.5v p-p for max1233, v in = 4.096v p-p for max1234, 50ksps, f sclk = 10mhz) signal-to-noise plus distortion sinad 69 db
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller _______________________________________________________________________________________ 3 electrical characteristics (continued) (dv dd = av dd = +2.7v to +3.6v (max1233), dv dd = av dd = +4.75v to +5.25v (max1234), external reference v ref = 2.5v (max1233), v ref = 4.096v (max1234); f sclk = 10mhz, f sample = 50ksps, 12-bit mode, 0.1? capacitor at ref, t a = -40 c to +85 c, unless otherwise noted. typical values are at t a = +25 c.) parameter symbol conditions min typ max units total harmonic distortion thd -84 db spurious-free dynamic range sfdr 84 db full-power bandwidth -3db point 0.5 mhz full-linear bandwidth sinad > 67db 50 khz conversion rate internal oscillator frequency 8 11.5 mhz aperture delay 30 ns aperture jitter <50 ps maximum serial clock frequency f sclk 10 mhz duty cycle 30 70 % auxiliary analog inputs (aux1, aux2) input voltage range 0v ref v input leakage current channel not selected or conversion stopped 0.1 1a input capacitance 34 pf battery monitor inputs (bat1, bat2) input voltage range 0.5 6.0 v sampling battery 10 k input impedance battery monitor off 1 g accuracy internal reference -3 +3 % temperature measurement temperature range -40 +85 c differential method (note 4) 1.6 resolution single measurement method (note 5) 0.3 c differential method (note 4) 3 accuracy single measurement method (note 5) 2 c internal adc reference 2.5v mode, t a = +25 c 2.470 2.500 2.530 reference output voltage v ref 1.0v mode, t a = +25 c 0.980 1.000 1.020 v output tempco tcv ref 60 ppm/ c reference output impedance normal operation 250 reference short-circuit current 18 ma external adc reference (internal reference disabled, reference applied to ref) reference input voltage range (note 6) 1.0 v dd v input impedance cs = gnd or v dd 1g v ref = +2.5v at 50ksps (max1233) 5 10 v ref = +4.096v at 50ksps (max1234) 8 15 input current shutdown/between conversions 0.1 ?
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 4 _______________________________________________________________________________________ electrical characteristics (continued) (dv dd = av dd = +2.7v to +3.6v (max1233), dv dd = av dd = +4.75v to +5.25v (max1234), external reference v ref = 2.5v (max1233), v ref = 4.096v (max1234); f sclk = 10mhz, f sample = 50ksps, 12-bit mode, 0.1? capacitor at ref, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) parameter symbol conditions min typ max units digital-to-analog converter dc accuracy resolution 8bits integral linearity error inl (note 7) 1.0 lsb differential linearity error dnl no missing codes 1.0 lsb offset error v os (note 8) 1 25 mv offset error temperature coefficient 1 ppm/ c full-scale error code = 255, no load 5 % full-scale error temperature coefficient code = 255, no load 10 ppm/ c dynamic performance voltage output slew rate positive and negative 0.4 v/? output settling time 0.5lsb; 50k and 50pf load (note 9) 20 ? glitch impulse code 127 to 128 40 nv/s wake-up time from shutdown 50 s dac output internal dac reference v refdac (note 10) 0.85 ? av dd 0.9 ? av dd 0.95 ? av dd v code = 255; 0 to 100? 0.5 output load regulation code = 0; 0 to 100? 0.5 lsb output resistance power-down mode 1.0 m touch-screen controller y+, x+ 7 on-resistance y-, x- 9 touch-detection internal pullup resistance x+ to av dd 1m keypad controller pullup resistance c4, c3, c2, c1 (note 11) 0.5 k pulldown resistance r4, r3, r2, r1 (note 11) 16 k digital interface digital inputs (sclk, cs , din, r_, c_) input voltage low v il 0.3 ? dv dd v input voltage high v ih 0.7 ? dv dd v input leakage current i l 0.1 1a
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller _______________________________________________________________________________________ 5 electrical characteristics (continued) (dv dd = av dd = +2.7v to +3.6v (max1233), dv dd = av dd = +4.75v to +5.25v (max1234), external reference v ref = 2.5v (max1233), v ref = 4.096v (max1234); f sclk = 10mhz, f sample = 50ksps, 12-bit mode, 0.1? capacitor at ref, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) parameter symbol conditions min typ max units input capacitance c in 15 pf digital output (dout) i sink = 2ma 0.4 output voltage low v ol i sink = 4ma 0.8 v output voltage high v oh i source = 1.5ma dv dd - 0.5 v digital output ( busy , penirq , keyirq , r_, c_) output voltage low v ol i sink = 0.2ma 0.4 v output voltage high v oh i source = 0.2ma dv dd - 0.5 v power requirements max1233 2.7 3 3.6 supply voltage (note 12) av dd / dv dd max1234 4.75 5 5.25 v idle; all blocks shut down 0.5 5 only adc on; f sample = 20ksps 150 500 only dac on; no load 150 230 analog and digital supply current i avdd + i dvdd only internal reference on 670 900 ? timing characteristics sclk clock period t cp 100 ns sclk pulse width high t ch 40 ns sclk pulse width low t cl 40 ns din to sclk rise setup t ds 40 ns sclk rise to din hold t dh 0ns sclk fall to dout valid t dov c load = 50pf 40 ns cs fall to dout enabled t dv c load = 50pf 45 ns cs rise to dout disabled t dod c load = 50pf 40 ns cs fall to sclk rise t css 40 ns cs fall to sclk ignored t csh 0ns sclk rise to r_/c_ data valid t gpo c load = 50pf (note 13) 230 ns cs pulse width high t csw 40 ns note 1: tested at dv dd = av dd = +2.7v (max1233), dv dd = av dd = +5v (max1234). note 2: relative accuracy is the deviation of the analog value at any code from its theoretical value after the offset and gain errors have been removed. note 3: offset nulled. note 4: difference between temp1 and temp2; temperature in ? = (v temp2 - v temp1 ) 2680?/v. no calibration is necessary. note 5: temperature coefficient is -2.1mv/?. determine absolute temperature by extrapolating from a calibrated value. note 6: adc performance is limited by the conversion noise floor, typically 300? p-p . an external reference below 2.5v can compromise the adc performance. note 7: guaranteed from code 5 to 255.
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 6 _______________________________________________________________________________________ electrical characteristics (continued) (dv dd = av dd = +2.7v to +3.6v (max1233), dv dd = av dd = +4.75v to +5.25v (max1234), external reference v ref = 2.5v (max1233), v ref = 4.096v (max1234); f sclk = 10mhz, f sample = 50ksps, 12-bit mode, 0.1? capacitor at ref, t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) note 8: the offset value extrapolated from the range over which the inl is guaranteed. note 9: output settling time is measured by stepping from code 5 to 255, and from code 255 to 5. note 10: actual output voltage at full scale is 255/256 v refdac . note 11: resistance is open when configured as gpio or in shutdown. note 12: av dd and dv dd should not differ by more than 300mv. note 13: when configured as gpio. sclk din dout note: timing not to scale. r_/c_ cs t cl t dh t dv t ds t ch t css t cp t csh t csw t csh t css t dod t dov t gpo timing diagram
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller _______________________________________________________________________________________ 7 shutdown current vs. analog supply voltage max1233/34 toc01 av dd (v) shutdown current (na) 5.2 4.7 4.2 3.7 3.2 50 100 150 200 250 300 0 2.7 shutdown current vs. temperature max1233/34 toc02 temperature ( c) shutdown current (na) 80 60 40 20 0 -20 50 100 150 200 250 300 0 -40 internal oscillator frequency vs. analog supply voltage max1233/34 toc03 av dd (v) internal oscillator frequency (mhz) 5.2 4.7 4.2 3.7 3.2 8.2 8.4 8.6 8.8 9.0 9.2 9.4 9.6 9.8 10.0 8.0 2.7 max1233/max1234 internal oscillator frequency vs. temperature max1233/34 toc04 temperature ( c) internal oscillator frequency (mhz) 80 60 40 20 0 -20 8.8 9.0 9.2 9.4 9.6 9.8 8.6 -40 max1234, av dd = +5.0v max1233, av dd = +3.0v temp1 diode voltage vs. analog supply voltage max1233/34 toc05 av dd (v) temp1 diode voltage (v) 5.2 4.7 4.2 3.7 3.2 0.52 0.54 0.56 0.58 0.60 0.62 0.64 0.66 0.68 0.70 0.50 2.7 temp1 diode voltage vs. temperature max1233/34 toc06 temperature ( c) temp1 diode voltage (v) 80 65 -25 -10 5 35 20 50 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.40 -40 temp2 diode voltage vs. analog supply voltage max1233/34 toc07 av dd (v) temp2 diode voltage (v) 5.2 4.7 4.2 3.7 3.2 0.65 0.70 0.75 0.80 0.60 2.7 temp2 diode voltage vs. temperature max1233/34 toc08 temperature ( c) temp2 diode voltage (v) 80 65 50 35 20 5 -10 -25 0.65 0.70 0.75 0.80 0.85 0.90 0.60 -40 typical operating characteristics (av dd = dv dd = 3v (max1233) or 5v (max1234), external v ref = +2.5v (max1233), external v ref = +4.096v (max1234), f sclk = 10mhz (50% duty cycle), f sample = 20ksps, c load = 50pf, 0.1? capacitor at ref, t a = +25?, unless otherwise noted.)
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 8 _______________________________________________________________________________________ typical operating characteristics (continued) (av dd = dv dd = 3v (max1233) or 5v (max1234), external v ref = +2.5v (max1233), external v ref = +4.096v (max1234), f sclk = 10mhz (50% duty cycle), f sample = 20ksps, c load = 50pf, 0.1? capacitor at ref, t a = +25?, unless otherwise noted.) adc differential nonlinearity vs. output code max1233/34 toc10 output code dnl (lsb) 4000 3500 2500 3000 1000 1500 2000 500 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 0 adc offset error vs. analog supply voltage max1233/34 toc11 av dd (v) offset error (lsb) 5.2 4.7 3.2 3.7 4.2 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0 -2.0 2.7 adc offset error vs. temperature max1233/34 toc12 temperature ( c) offset error (lsb) 80 60 -20 0 20 40 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0 -2.0 -40 adc gain error vs. analog supply voltage max1233/34 toc13 av dd (v) gain error (lsb) 5.2 4.7 3.2 3.7 4.2 -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0 -2.0 2.7 adc gain error vs. temperature max1233/34 toc14 temperature ( c) gain error (lsb) -1.5 -1.0 -0.5 0 0.5 1.0 1.5 2.0 -2.0 80 60 -20 0 20 40 -40 adc integral nonlinearity vs. output code max1233/34 toc09 output code inl (lsb) 4000 3500 2500 3000 1000 1500 2000 500 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1.0 -1.0 0
max1233/max1234 -0.050 -0.075 -0.100 -0.025 0 0.025 0.050 0.075 0 100 200 300 dac integral nonlinearity vs. code max1233/34 toc19 code inl (lsb) 50 150 250 dac differential nonlinearity vs. output code max1233/34 toc20 output code dnl (lsb) 250 200 150 100 50 -0.075 -0.500 -0.025 0 0.025 0.050 0.075 -0.100 0 300 typical operating characteristics (continued) (av dd = dv dd = 3v (max1233) or 5v (max1234), external v ref = +2.5v (max1233), external v ref = +4.096v (max1234), f sclk = 10mhz (50% duty cycle), f sample = 20ksps, c load = 50pf, 0.1? capacitor at ref, t a = +25?, unless otherwise noted.) 15kv esd-protected touch-screen controllers include dac and keypad controller _______________________________________________________________________________________ 9 adc external reference input current vs. sampling rate max1233/34 toc15 f sample (hz) reference current ( a) 10k 1k 2 4 6 8 0 100 100k max1233 v ref = +2.5v adc supply current vs. sampling rate max1233/34 toc16 f sample (hz) supply current ( a) 10k 100 1 10 100 1000 0.1 1 100k 10 1k adc supply current vs. supply voltage max1233/34 toc17 av dd (v) supply current ( a) 50 100 150 200 250 0 5.2 4.7 4.2 3.7 3.2 2.7 external ref f sample = 20ksps adc supply current vs. temperature max1233/34 toc18 temperature ( c) supply current ( a) 20 40 60 80 100 120 140 0 av dd = +3v 80 60 -20 0 20 40 -40
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 10 ______________________________________________________________________________________ adc reference voltage vs. analog supply voltage max1233/34 toc25 av dd (v) v ref (v) v ref (v) 2.475 2.500 2.525 2.550 2.450 0.990 1.000 1.010 1.020 0.980 5.2 4.7 4.2 3.7 3.2 2.7 v ref = 1.0v v ref = 2.5v adc reference voltage vs. temperature temperature ( c) v ref (v) 2.45 2.50 2.55 2.60 2.40 v ref (v) 0.875 1.000 1.125 1.250 0.750 v ref = 2.5v max1233/34 toc26 80 60 -20 0 20 40 -40 v ref = 1.0v 0.75 0.25 0 -0.25 -0.50 0.50 -0.75 2.5 4.0 3.0 3.5 4.5 5.0 5.5 dac full-scale error vs. analog supply voltage max1233/34 toc21 av dd (v) full-scale error (lsb) 1.2 0.4 0 -0.4 -0.8 0.8 -1.2 full-scale error (%) 0.75 0.25 0 -0.25 -0.50 0.50 -0.75 -40 20 -20 0 40 60 80 dac full-scale error vs. temperature max1233/34 toc22 temperature ( c) full-scale error (lsb) 1.2 0.4 0 -0.4 -0.8 0.8 -1.2 full-scale error (%) dac supply current vs. analog supply voltage max1233/34 toc23 av dd (v) dac supply current ( a) 50 100 150 200 250 0 5.2 4.7 4.2 3.7 3.2 2.7 max1233/34 toc24 temperature ( c) dac supply current ( a) 80 60 -20 0 20 40 25 50 75 100 125 150 175 200 0 -40 dac supply current vs. temperature typical operating characteristics (continued) (av dd = dv dd = 3v (max1233) or 5v (max1234), external v ref = +2.5v (max1233), external v ref = +4.096v (max1234), f sclk = 10mhz (50% duty cycle), f sample = 20ksps, c load = 50pf, 0.1? capacitor at ref, t a = +25?, unless otherwise noted.)
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 11 typical operating characteristics (continued) (av dd = dv dd = 3v (max1233) or 5v (max1234), external v ref = +2.5v (max1233), external v ref = +4.096v (max1234), f sclk = 10mhz (50% duty cycle), f sample = 20ksps, c load = 50pf, 0.1? capacitor at ref, t a = +25?, unless otherwise noted.) adc reference supply current vs. analog supply voltage max1233/34 toc27 av dd (v) supply current ( a) 4.7 4.2 3.7 3.2 600 650 700 750 550 2.7 5.2 reference supply current vs. temperature max1233/34 toc28 temperature ( c) supply current ( a) 600 650 700 750 550 80 65 -25 -10 5 35 20 50 -40 pin name function 1dv dd positive digital supply voltage, +2.7v to +3.6v for max1233, +4.75v to +5.25v for max1234. bypass with a 0.1? capacitor. must be within 300mv of av dd . 2av dd positive analog supply voltage, +2.7v to +3.6v for max1233, +4.75v to +5.25v for max1234. bypass with a 0.1? capacitor. must be within 300mv of dv dd . 3* x+ x+ position input 4* y+ y+ position input 5* x- x- position input 6* y- y- position input 7 gnd analog and digital ground 8* bat1 battery monitoring input 1. measures battery voltages up to 6v. 9* bat2 battery monitoring input 2. measures battery voltages up to 6v. 10* aux1 auxiliary analog input 1 to adc. measures analog voltages from zero to v ref . 11* aux2 auxiliary analog input 2 to adc. measures analog voltages from zero to v ref . 12 ref voltage reference output/input. reference voltage for analog-to-digital conversion. in internal reference mode, the reference buffer provides a 2.5v or 1.0v nominal output. in external reference mode, apply a reference voltage between 1.0v and av dd . bypass ref to gnd with a 0.1? capacitor in the external reference mode only. 13 dacout dac voltage output; 0.9 av dd full scale 14 r4 keypad row 4. can be reconfigured as gpio3. 15 r3 keypad row 3. can be reconfigured as gpio2. 16 r2 keypad row 2. can be reconfigured as gpio1. 17 r1 keypad row 1. can be reconfigured as gpio0. 18 c1 keypad column 1. can be reconfigured as gpio4. pin description
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 12 ______________________________________________________________________________________ detailed description the max1233/max1234 are 4-wire touch-screen con- trollers. figure 1 shows the functional diagram of the max1233/max1234. each device includes a 12-bit sam- pling adc, 8-bit voltage output dac, keypad scanner that can also be configured as a gpio, internal clock, reference, temperature sensor, two battery monitor inputs, two auxiliary analog inputs, spi/qspi/ microwire-compatible serial interface, and low on- resistance switches for driving touch screens. the 16-bit register inside the max1233/max1234 allows for easy control and stores results that can be read at any time. the busy output indicates that a functional operation is in progress. the penirq and keyirq outputs, respectively, indicate that a screen touch or a key press has occurred. touch-screen operation the 4-wire touch-screen controller works by creating a voltage gradient across the vertical or horizontal resis- tive touch screen connected to the analog inputs of the max1233/max1234, as shown in figure 2. the voltage across the touch-screen panels is applied through inter- nal mosfet switches that connect each resistive layer to av dd and ground. for example, to measure the y position when a pointing device presses on the touch screen, the y+ and y- drivers are turned on, connecting one side of the vertical resistive layer to av dd and the other side to ground. the horizontal resistive layer func- tions as a sense line. one side of this resistive layer gets connected to the x+ input, while the other side is left open or floating. the point where the touch screen is pressed brings the two resistive layers in contact and creates a voltage-divider at that point. the data convert- er senses the voltage at the point of contact through the x+ input and digitizes it. 12-bit adc analog inputs figure 3 shows a block diagram of the adc? analog input section including the input multiplexer, the differen- tial input, and the differential reference. the input multi- plexer switches between x+, x-, y+, y-, aux1, aux2, bat1, bat2, and the internal temperature sensor. the time required for the t/h to acquire an input signal is a function of how quickly its input capacitance is charged. if the input signal? source impedance is high, the acquisition time lengthens, and more time must be allowed. the acquisition time (t acq ) is the maximum time the device takes to acquire the input signal to 12- bit accuracy. configure t acq by writing to the adc control register. see table 1 for the maximum input sig- nal source impedance (r source ) for complete settling during acquisition. accommodate higher source impedances by placing a 0.1? capacitor between the analog input and gnd. input bandwidth the adc? input-tracking circuitry has a 0.5mhz small- signal bandwidth. to avoid high-frequency signals being aliased into the frequency band of interest, anti- alias filtering is recommended. pin name function 19 c2 keypad column 2. can be reconfigured as gpio5. 20 c3 keypad column 3. can be reconfigured as gpio6. 21 c4 keypad column 4. can be reconfigured as gpio7. 22 keyirq active-low keypad interrupt. keyirq is low when a key press is detected. 23 penirq active-low pen touch interrupt. penirq is low when a screen touch is detected. 24 dout serial data output. data is clocked out at sclk falling edge. high impedance when cs is high. 25 busy active-low busy output. busy goes low and stays low during each functional operation. the host controller should wait until busy is high again before using the serial interface. 26 din serial data input. data is clocked in on the rising edge of sclk. 27 sclk serial clock input. clocks data in and out of the serial interface and sets the conversion speed (duty cycle must be 30% to 70%). 28 cs active-low chip select. data is not clocked into din unless cs is low. when cs is high, dout is high impedance. ?p exposed pad. internally connected to gnd. connect to a large ground plane to maximize thermal performance. not intended as an electrical connection point. pin description (continued) * esd protected: ?kv contact, ?5kv air.
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 13 ref *x+ dacout dout keypad controller and gpio mux 12-bit adc *x- oscillator serial data i/o temp sensor internal reference 2.5v/1.0v registers and scan state control 8-bit dac *y+ *y- *bat1 *bat2 *aux1 *aux2 battery monitor battery monitor sclk din c1 c2 c3 c4 r1 r2 r3 r4 x/y switches ref dac cs penirq keyirq busy max1233 max1234 *esd protected figure 1. block diagram gnd force line sense line force line y- y+ +in +ref -ref -in +av dd x+ sense line figure 2. touch-screen measurement table 1. maximum input source impedance acquisition time (?) resolution (bits) maximum r source for complete settling during acquisition (k ) 1.5 8 2.6 1.5 10 2.0 1.5 12 1.5 5.0 8 23 5.0 10 19 5.0 12 15 95 8 560 95 10 470 95 12 400
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 14 ______________________________________________________________________________________ analog input protection internal protection diodes that clamp the analog input to av dd and gnd allow the analog input pins to swing from gnd - 0.3v to av dd + 0.3v without damage. analog inputs must not exceed av dd by more than 50mv or be lower than gnd by more than 50mv for accurate conversions. if an off-channel analog input voltage exceeds the supplies, limit the input current to 50ma. all analog inputs are also fully esd protected to ?kv, using the contact-discharge method and ?5kv using the air-gap method specified in iec- 1000-4-2. reference for adc internal reference the max1233/max1234 offer an internal voltage refer- ence for the adc that can be set to +1.0v or +2.5v. the max1233/max1234 typically use the internal reference for battery monitoring, temperature measurement, and for converter - ref +ref +in -in v bat1 aux1 aux2 gnd 2.5v/1.0v reference ref on/off x+ x- temp2 y+ y- 7.5k 2.5k v bat2 7.5k temp1 battery on 2.5k battery on +av dd v ref max1233 max1234 figure 3. simplified diagram of analog input section
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 15 measurement of the auxiliary inputs. figure 4 shows the on-chip reference circuitry of the max1233/max1234. set the internal reference voltage by writing to the rfv bits in the adc control register (see tables 4, 5, and 12). the max1233/max1234 can accept an external refer- ence connected to ref for adc conversion. external reference the max1233/max1234 can accept an external refer- ence connected to the ref pin for adc conversions. the internal reference should be disabled (res1 = 1) when using an external reference. at a conversion rate of 50ksps, an external reference at ref must deliver up to 15? of load current and have 50 or less output impedance. if the external reference has high output impedance or is noisy, bypass it close to the ref pin with a 0.1? capacitor. selecting internal or external reference set the type of reference being used by programming the adc control register. to select the internal refer- ence, clock zeros into bits [a/d3:a/d0] and a zero to bit res1, as shown in the control registers section. to change to external reference mode, clock zeros into bits [a/d3:a/d0] and a one to bit res1. see table 13 for more information about selecting an internal or external reference for the adc. reference power modes auto power-down mode (res1 = res0 = 0) the max1233/max1234 are in auto power-down mode at initial power-up. set the res1 and res0 bits to zero to use the max1233/max1234 in the auto power-down mode. in this mode, the internal reference is normally off. when a command to perform a battery measure- ment, temperature measurement, or auxiliary input measurement is written to the adc control register, the device powers on the internal reference, waits for the internal reference to settle, completes the requested scan, and powers down the internal reference. the ref- erence power delay depends upon the adc resolution selected (see table 8). do not bypass ref with an external capacitor when performing scans in auto power-down mode. full-power mode (res1 = 0, res0 = 1) in the full-power mode, the res1 bit is set low and res0 bit is set high. in this mode, the device is pow- ered up and the internal adc reference is always on. the max1233/max1234 internal reference remains fully powered after completing a scan. internal clock the max1233/max1234 operate from an internal oscil- lator, which is accurate to within 20% of the 10mhz specified clock rate. the internal oscillator controls the timing of the acquisition, conversion, touch-screen set- tling, reference power-up, and keypad debounce times. 8-bit dac the max1233/max1234 have a voltage-output, true 8-bit monotonic dac with less than 1lsb integral nonlinearity error and less than 1lsb differential nonlinearity error. it requires a supply current of only 150? (typ) and pro- vides a buffered voltage output. the dac is at midscale code at power-up and remains there until a new code is written to the dac register. during shutdown, the dac? output is pulled to ground with a 1m load. the internal dac can be used in various system applica- tions such as lcd/tft-bias control, automatic tuning (vco), power amplifier bias control, programmable threshold levels, and automatic gain control (agc). the 8-bit dac in the max1233/max1234 employs a current-steering topology as shown in figure 5. at the core of this dac is a reference voltage-to-current con- verter (v/i) that generates a reference current. this cur- rent is mirrored to 255 equally weighted current sources. dac switches control the outputs of these cur- rent mirrors so that only the desired fraction of the total current-mirror currents is steered to the dac output. the current is then converted to a voltage across a resistor, and the output amplifier buffers this voltage. dac output voltage the 8-bit dac code is binary unipolar with 1lsb = (v ref /256). the dac has a full-scale output voltage of (0.9 av dd - 1lsb). +1.25v bandgap 2x ref pin optional 3r 2r figure 4. block diagram of the internal reference
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 16 ______________________________________________________________________________________ output buffer the dac voltage output is an internally buffered unity- gain follower that slews at up to ?.4v/?. the output can swing from zero to full scale. with a 1/4fs to 3/4fs output transition, the amplifier output typically settles to 1/2lsb in less than 5? when loaded with 10k in par- allel with 50pf. the buffer amplifier is stable with any combination of resistive loads >10k and capacitive loads <50pf. power-on reset all registers of the max1233/max1234 power up at a default zero state, except the dac data register, which is set to 10000000, so the output is at midscale. keypad controller and gpio the keypad controller is designed to interface a matrix- type 4 rows 4 columns (16 keys or fewer) keypad to a host controller. the key control register controls keypad interrupt, keypad scan, and keypad debounce times. the keymask and columnmask registers enable mask- ing of a particular key or an entire column of the keypad when they are not in use. the max1233/max1234 offer two keypad data registers. kpdata1 is the pending reg- ister. kpdata2 holds keypad scan results of only the unmasked keys. if 12 or fewer keys are being monitored, one or more of the row/column pins of the max1233/max1234 can be software programmed as gpio pins. touch-screen detection touch-screen detection can be enabled or disabled by writing to the adc control register as shown in table 4. touch-screen detection is disabled at initial power-up. once touch-screen detection is enabled, the y- driver is on and the y- pin is connected to gnd. the x+ pin is internally pulled to av dd through a 1m resistor as shown in figure 6. when the screen is touched, the x+ pin is pulled to gnd through the touch screen and a touch is detected. when the 1m pullup resistor is first connected, the x+ pin can be floating near ground. to prevent false touch detection in this case, the x+ pin is precharged high for 0.1? using the 7 pmos driver before touch detection begins. key-press detection key-press detection can be enabled or disabled by writing to the keypad control register as shown in table 17. key-press detection is disabled at initial power-up. once key-press detection is enabled, the c_ pins are internally connected to dv dd and the r_ pins are inter- nally pulled to gnd through a 16k resistor. when a key is pressed, the associated row pin is pulled to dv dd and the key press is detected. figure 7 shows the key-press detection circuitry. interrupts pen interrupt request ( penirq ) the penirq output can be used to alert the host con- troller of a screen touch. the penirq output is normally high and goes low after a screen touch is detected. sw1 sw2 sw255 out v ref figure 5. dac current-steering topology s2 s1 1m +av dd x+ y+ x- y- touch-screen detector penirq touch screen figure 6. touch-screen detection block diagram
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 17 r2 c1 c2 c3 c4 r1 r3 r4 drivers pull high or go three-state keypad to keypad wakeup and debounce logic simplified keypad circuitry figure 7. key-press detection circuitry x+ data read dout touch- screen data penirq busy cs figure 8a. timing diagram for touch-initiated screen scan x+ dout data read touch- screen data din penirq busy cs figure 8b. timing diagram for host-initiated screen scan
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 18 ______________________________________________________________________________________ penirq returns high only after a touch-screen scan is completed. penirq does not go low again until one of the touch-screen data registers is read. figures 8a and 8b show the timing diagrams for the penirq pin. keypad interrupt request ( keyirq ) the keyirq output can be used to alert the host con- troller of a key press. the keyirq output is normally high and goes low after a key press is detected. keyirq returns high only after a key-press scan is completed. keyirq does not go low again until one of the key-press data registers is read. figures 9a and 9b show the timing diagrams for the keyirq pin. busy indicator ( busy ) busy informs the host processor that a scan is in progress. busy is normally high and goes low and stays low during each functional operation. the host controller should wait until busy is high again before using the serial interface. digital interface the max1233/max1234 interface to the host controller through a standard 3-wire serial interface at up to 10mhz. din and cs are the digital inputs to the max1233/max1234. dout is the serial data output. data is clocked out at the sclk falling edge and is high impedance when cs is high. when performing an adc scan, cs must de-assert high before the end of the first conversion, otherwise the conversion results will not be stored. penirq and keyirq communicate interrupts from the touch-screen and keypad controllers to the host processor when a screen touch or a key press is detected. busy informs the host processor that a scan is in progress. in addition to these digital i/os, the row and column pins of the keypad controller can be programmed as gpio pins. communications protocol the max1233/max1234 are controlled by reading from and writing to registers through the 3-wire serial inter- face. these registers are addressed through a 16-bit command that is sent prior to the data. the command is shown in table 2. the first 16 bits after the falling edge of cs contain the command word. the command word begins with an r/ w bit, which specifies the direction of data flow on the serial bus. bits 14 through 7 are reserved for future use. bit 6 specifies the page of memory in which the desired register is located. the last 6 bits specify the address of the desired register. the next 16 bits of data are read from or written to the address specified in the command word. after 32 clock cycles, the interface automatically increments its address pointer and con- tinues reading or writing until the rising edge of cs , or until it reaches the end of the page. data read dout touch- screen data r_ keyirq busy cs figure 9a. timing diagram for key-press-initiated debounce scan r_ dout data read touch- screen data din keyirq busy cs figure 9b. timing diagram for host-initiated keypad debounce scan bit15 msb bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 lsb r/ w res res res res res res res res page add5 add4 add3 add2 add1 add0 table 2. command word format
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 19 write command (hex) read command (hex) register name bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 0x8000 x 0 0 0 0 x11 x10 x9 x8 x7 x6 x5 x4 x3 x2 x1 x0 0x8001 y 0 0 0 0 y11 y10 y9 y8 y7 y6 y5 y4 y3 y2 y1 y0 0x8002 z1 0 0 0 0 z1_11 z1_10 z1_9 z1_8 z1_7 z1_6 z1_5 z1_4 z1_3 z1_2 z1_1 z1_0 0x8003 z2 0 0 0 0 z2_11 z2_10 z2_9 z2_8 z2_7 z2_6 z2_5 z2_4 z2_3 z2_2 z2_1 z2_0 0x8004 kpd k15 k14 k13 k12 k11 k10 k9 k8 k7 k6 k5 k4 k3 k2 k1 k0 0x8005 bat1 0 0 0 0 b1_11 b1_10 b1_9 b1_8 b1_7 b1_6 b1_5 b1_4 b1_3 b1_2 b1_1 b1_0 0x8006 bat2 0 0 0 0 b2_11 b2_10 b2_9 b2_8 b2_7 b2_6 b2_5 b2_4 b2_3 b2_2 b2_1 b2_0 0x8007 aux1 0 0 0 0 a1_11 a1_10 a1_9 a1_8 a1_7 a1_6 a1_5 a1_4 a1_3 a1_2 a1_1 a1_0 0x8008 aux2 0 0 0 0 a2_11 a2_10 a2_9 a2_8 a2_7 a2_6 a2_5 a2_4 a2_3 a2_2 a2_1 a2_0 0x8009 temp1 0 0 0 0 t1_11 t1_10 t1_9 t1_8 t1_7 t1_6 t1_5 t1_4 t1_3 t1_2 t1_1 t1_0 0x800a temp2 0 0 0 0 t2_11 t2_10 t2_9 t2_8 t2_7 t2_6 t2_5 t2_4 t2_3 t2_2 t2_1 t2_0 0x000b 0x800b dac data 0 0 0 0 0 0 0 0 da7 da6 da5 da4 da3 da2 da1 da0 0x000f 0x800f gpio data gpd7 gpd6 gpd5 gpd4 gpd3 gpd2 gpd1 gpd0 0 0 0 00000 0x8010 kpdata1 k1_15 k1_14 k1_13 k1_12 k1_11 k1_10 k1_9 k1_8 k1_7 k1_6 k1_5 k1_4 k1_3 k1_2 k1_1 k1_0 0x8011 kpdata2 k2_15 k2_14 k2_13 k2_12 k2_11 k2_10 k2_9 k2_8 k2_7 k2_6 k2_5 k2_4 k2_3 k2_2 k2_1 k2_0 0x0040 0x8040 adc control p en sts adsts a/d3 a/d2 a/d1 a/d0 res1 res0 avg1 avg0 cnr1 cnr0 st2 st1 st0 rfv 0x0041 0x8041 key control k eysts1 keysts0 dbn2 dbn1 dbn0 hld2 hld1 hld0 0 0 0 00000 0x0042 0x8042 dac control dapd 0 0 0 0 0 0 0 0 0 0 00000 0x004e 0x804e gpio pullup pu7 pu6 pu5 pu4 pu3 pu2 pu1 pu0 0 0 0 00000 0x004f 0x804f gpio control gp7 gp6 gp5 gp4 gp3 gp2 gp1 gp0 oe7 oe6 oe5 oe4 oe3 oe2 oe1 oe0 0x0050 0x8050 kpkeymask km15 km14 km13 km12 km11 km10 km9 km8 km7 km6 km5 km4 km3 km2 km1 km0 0x0051 0x8051 kpcolumnmask cm4 cm3 cm2 cm1 0 0 0 0 0 0 0 00000 table 3. register summary note: all other registers are reserved and should always be 0. power-on reset state is dac data at midscale (0x0080), all other reg- isters are 0.
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 20 ______________________________________________________________________________________ in order to read the entire first page of memory, for example, the host processor must send the max1233/max1234 the command 0x8000 h . the max1233/max1234 then begin clocking out 16-bit data starting with the x-data register. in order to write to the second page of memory, the host processor sends the max1233/max1234 the command 0x0040 h . the suc- ceeding data is then written in 16-bit words beginning with the adc control register. figures 10a and 10b show a complete write and read operation, respectively, between the processor and the max1233/max1234. memory map the max1233/max1234s?internal memory is divided into two pages?ne for data and one for control, each of which contains thirty-two 16-bit registers. control registers table 3 provides a summary of all registers and bit locations of the max1233/max1234. adc control register the adc measures touch position, touch pressure, bat- tery voltage, auxiliary analog inputs, and temperature. the adc control register determines which input is selected and converted. tables 4 and 5 show the for- mat and bit descriptions for the adc control register. din dout sclk d15 d15 is read/write bit low for write d15?0 command word timing not to scale. d0 d15 d0 d15?0 data word three- state cs write operation three- state figure 10a. timing diagram of write operation sclk three-state d15 d14 d15?0 command word d0 three-state d0 d15 dout din d0 d15 data word data word cs read operation figure 10b. timing diagram of read operation bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 pensts adsts a/d3 a/d2 a/d1 a/d0 res1 res0 avg1 avg0 cnr1 cnr0 st2 st1 st0 rfv table 4. adc control register (write 0x0040/read 0x8040)
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 21 bits 14-15: pen interrupt status and adc status bits these bits are used to control or monitor adc scans. bits 10-13: adc scan select these bits control which input to convert and which con- verter mode is used. the bits are identical regardless of a read or write. see table 7 for details about using these bits. bits 8-9: adc resolution control these bits specify the adc resolution and are identical regardless of read or write. table 8 shows how to use these bits to set the resolution. bits 6-7: converter averaging control these bits specify the number of data averages the converter performs. table 9 shows how to program for the desired number of averages. when averaging is used, adsts and busy indicate the converter is busy until all conversions needed for the averaging finish. these bits are identical, regardless of read or write. bits 4-5: adc conversion rate control these bits specify the internal conversion rate, which the adc uses to perform a single conversion, as shown in table 10. lowering the conversion rate also reduces power consumption. these bits are identical, regard- less of read or write. bit name description 15 (msb) pensts read: pen interrupt status; write: sets interrupt initiated touch-screen scans 14 adsts read: adc status; write: stops adc 13 a/d3 selects adc scan functions 12 a/d2 selects adc scan functions 11 a/d1 selects adc scan functions 10 a/d0 selects adc scan functions 9 res1 controls adc resolution 8 res0 controls adc resolution 7 avg1 controls adc result averaging 6 avg0 controls adc result averaging 5 cnr1 controls adc conversion rate 4 cnr0 controls adc conversion rate 3 st2 controls touch-screen settling wait time 2 st1 controls touch-screen settling wait time 1 st0 controls touch-screen settling wait time 0 (lsb) rfv chooses 1.0v or 2.5v reference table 5. adc control register bit descriptions (write 0x0040/read 0x8040) pensts adsts read function write function 00 no screen touch detected; scan or conversion in progress performs one scan and waits to detect a screen touch. upon detection, issues an interrupt and waits until told to scan by the host controller. 10 screen touch detected; scan or conversion in progress stops any ongoing scan and waits to detect a screen touch. upon detection, issues an interrupt and performs a scan. 01 no screen touch detected; data available stops any ongoing scan and waits to detect a screen touch. upon detection, issues an interrupt and waits until told to scan by the host controller. 11 screen touch detected; data available stops any ongoing scan and powers down the screen touch detection circuit. no screen touches are detected in this mode. table 6. adsts bit operation
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 22 ______________________________________________________________________________________ a/d3 a/d2 a/d1 a/d0 function 0000 configures the adc reference as selected by res [1:0] bits as shown in table 13. no measurement is performed. 0 0 0 1 measures x/y touch position and returns results to the x and y data registers. 0010 measures x/y touch position and z1/ z2 touch pressure and returns results to the x, y, z1, and z2 data registers. 0 0 1 1 measures x touch position and returns results to the x data register. 0 1 0 0 measures y touch position and returns results to the y data register. 0 1 0 1 measures z1/z2 touch pressure and returns results to the z1 and z2 data register. 0 1 1 0 measures battery input 1 through a 4:1 divider and returns results to the bat1 data register. 0 1 1 1 measures battery input 2 through a 4:1 divider and returns results to the bat2 data register. 1 0 0 0 measures auxiliary input 1 and returns results to the aux1 data register. 1 0 0 1 measures auxiliary input 2 and returns results to the aux2 data register. 1 0 1 0 measures temperature (single ended) and returns results to the temp1 data register. 1011 measures battery input 1, battery input 2, auxiliary input 1, auxiliary input 2, and temperature (differential), and returns results to the appropriate data registers. 1 1 0 0 measures temperature (differential) and returns results to the temp1 and temp2 data registers. 1 1 0 1 turns on y+, y- drivers. no measurement is performed. 1 1 1 0 turns on x+, x- drivers. no measurement is performed. 1 1 1 1 turns on y+, x- drivers. no measurement is performed. table 7. adc scan select (touch screen, battery, auxiliary channels, and temperature) res1 res0 adc resolution internally timed reference power-up delay* (?) 0 0 8 bit 31 0 1 8 bit 31 1 0 10 bit 37 1 1 12 bit 44 table 8. adc resolution control * applicable only for temperature, battery, or auxiliary measurements in auto power-up reference mode. avg1 avg0 function 0 0 no data averages (default) 0 1 4 data averages 1 0 8 data averages 1 1 16 data averages table 9. adc averaging control cnr1 cnr0 function 00 3.5?/sample (1.5? acquisition, 2? conversion) 01 3.5?/sample (1.5? acquisition, 2? conversion) 10 10?/sample (5? acquisition, 5? conversion) 11 100?/sample (95? acquisition, 5? conversion) table 10. adc conversion rate control
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 23 bits 1-3: touch-screen settling time control these bits specify the time delay from pen-touch detec- tion to a conversion start. this allows the selection of the appropriate settling time for the touch screen being used. table 11 shows how to set the settling time. these bits are identical, regardless of read or write. bit 0: adc internal reference voltage control this bit selects the adc internal reference voltage, either +1.0v or +2.5v. this bit is identical, regardless of read or write. the reference control bit is shown in table 12. internal adc reference power-down control the adc control register controls the power setting of the internal adc reference. zeros must be written to bits a/d3?/d0 to control internal reference power-up followed by the appropriate logic at the res1 and res0 bits. table 13 shows the internal adc reference power- down control. dac control register the msb in this control register determines the power- down control of the on-board dac. table 14 shows the dac control register. writing a zero to bit 15 (dapd) powers up the dac, while writing a 1 powers down the dac. table 15 describes the dac control register con- tents, while table 16 shows the dac power-down bit. keypad control registers the keypad control register, keypad mask register, and keypad column mask control register control the key- pad scanner in the max1233/max1234. the keypad control register (table 17) controls scanning and debouncing, while the keypad mask register (table 22) and the keypad column mask control register (table 24), st2 st1 st0 settling time 0 0 0 settling time: 0? 0 0 1 settling time: 100? 0 1 0 settling time: 500? 0 1 1 settling time: 1ms 1 0 0 settling time: 5ms 1 0 1 settling time: 10ms 1 1 0 settling time: 50ms 1 1 1 settling time: 100ms table 11. touch-screen settling time control* * applicable only for x, y, z1, and z2 measurements. [a/d3:a/d0] res1 res0 a dc r ef er en c e source adc reference power mode 0000 0 0 internal power up, wait for reference to settle, and power down again for each temperature, battery, or auxiliary scan (auto power-up mode) 0000 0 1 internal always powered up 0000 1 0 external always powered down 0000 1 1 external always powered down table 13. internal adc reference auto power-up control rfv function 0 +1.0v reference 1 +2.5v reference table 12. adc reference control bit bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 dapd000000000000000 table 14. dac control register (write 0x0042/read 0x8042) bit name description 15 (msb) dapd dac powered down [14:0] 0 reserved table 15. dac control register descriptions dapc function 0 dac powered up 1 dac powered down table 16. dac power-down bit
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 24 ______________________________________________________________________________________ keysts1 keysts0 read function write function 00 no button press detected; scan or debounce in progress scans keypad once and waits to detect a button press. upon detection, issues an interrupt and waits for the host? instruction before scanning. 10 button press detected; scan or debounce in progress stops any ongoing scan and waits to detect a button press. upon detection, issues an interrupt and scans the keypad. 01 no button press detected; data available stops any ongoing scan and waits to detect a button press. upon detection, issues an interrupt and waits for the host? instruction before scanning. 11 button press detected; data available stops any ongoing scan and powers down the button press detection circuit. no button presses are detected in this mode. table 19. keysts1/keysts0 functions dbn2 dbn1 dbn0 function (ms) 0 0 0 debounce time: 2 0 0 1 debounce time: 10 0 1 0 debounce time: 20 0 1 1 debounce time: 50 1 0 0 debounce time: 60 1 0 1 debounce time: 80 1 1 0 debounce time: 100 1 1 1 debounce time: 120 table 20. keypad debounce time control bit name description 15 (msb) keysts1 read: keypad interrupt status; write: set interrupt initiated keypad scans 14 keysts0 read: keypad scan status; write: stop keypad scan 13 dbn2 keypad debounce time control 12 dbn1 keypad debounce time control 11 dbn0 keypad debounce time control 10 hld2 keypad hold time control 9 hld1 keypad hold time control 8 hld0 keypad hold time control [7:0] 0 reserved table 18. keypad control register bit descriptions (write 0x0041/read 0x8041) bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 keysts1 keysts0 dbn2 dbn1 dbn0 hld2 hld hld 00000000 table 17. keypad control register (write 0x0041/read 0x8041)
hld2 hld1 hld0 function 0 0 0 if a button is held, wait 100? before beginning next debounce scan 0 0 1 if a button is held, wait 1 debounce time before beginning the next debounce scan 0 1 0 if a button is held, wait 2 debounce times before beginning the next debounce scan 0 1 1 if a button is held, wait 3 debounce times before beginning the next debounce scan 1 0 0 if a button is held, wait 4 debounce times before beginning the next debounce scan 1 0 1 if a button is held, wait 5 debounce times before beginning the next debounce scan 1 1 0 if a button is held, wait 6 debounce times before beginning the next debounce scan 1 1 1 if a button is held, wait 7 debounce times before beginning the next debounce scan table 21. keypad hold time control max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 25 allowing certain keys to be masked from detection. tables 18?1 show the programmable bits of the keypad control register. tables 23, 24, and 25 show the program- mable bits of the keypad mask registers. the keypad controller and gpio section provides more details. gpio control register the gpio control register and the gpio pullup register allow the keypad controller? row and column inputs to be configured as up to eight parallel i/o pins. tables 26 and 27 show the gpio control register layout and control reg- ister descriptions. tables 28 and 29 show the gpio pullup disable register and associated descriptions. for more information, see the applications information section. bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 km15 km14 km13 km12 km11 km10 km9 km8 km7 km6 km5 km4 km3 km2 km1 km0 table 22. keypad key mask register bit descriptions (write 0x0050/read 0x8050) bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 cm4cm3cm2cm1000000000000 table 24. keypad column mask register (write 0x0051/read 0x8051) bit name description 15 km15 mask status register data update on individual key for row 4, column 4 14 km14 mask status register data update on individual key for row 3, column 4 13 km13 mask status register data update on individual key for row 2, column 4 12 km12 mask status register data update on individual key for row 1, column 4 11 km11 mask status register data update on individual key for row 4, column 3 10 km10 mask status register data update on individual key for row 3, column 3 9 km9 mask status register data update on individual key for row 2, column 3 8 km8 mask status register data update on individual key for row 1, column 3 7 km7 mask status register data update on individual key for row 4, column 2 6 km6 mask status register data update on individual key for row 3, column 2 5 km5 mask status register data update on individual key for row 2, column 2 4 km4 mask status register data update on individual key for row 1, column 2 3 km3 mask status register data update on individual key for row 4, column 1 2 km2 mask status register data update on individual key for row 3, column 1 1 km1 mask status register data update on individual key for row 2, column 1 0 km0 mask status register data update on individual key for row 1, column 1 table 23. keypad key mask register bit descriptions (write 0x0050/read 0x8050)
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 26 ______________________________________________________________________________________ data registers the data results from conversions or keypad scans are held in the data registers of the max1233/max1234. during power-up, all of these data registers with the exception of the dac data register default to 0000 h . the dac register defaults to 1000 h . analog input data registers table 30 shows the format of the x, y, z 1 , z 2 , bat1, bat2, aux1, aux2, temp1, and temp2 data registers. the data format for these registers is right justified beginning with bit 11. data written through the serial interface to these registers is not stored. keypad data registers table 31 shows the formatting of the keypad data regis- ters, while tables 32, 33, and 34 provide individual reg- ister bit descriptions. these registers have the same format as the keypad mask register. each bit repre- sents one key on the keypad. table 35 shows a map of a 16-key keypad. data written through the serial inter- face to these registers is not stored. bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 gp7 gp6 gp5 gp4 gp3 gp2 gp1 gp0 oe7 oe6 oe5 oe4 oe3 oe2 oe1 oe0 table 26. gpio control register (write 0x004f/read 0x804f) description bit name 10 15 gp7 c4 pin becomes gpio pin 7 c4 pin remains keypad column 4 14 gp6 c3 pin becomes gpio pin 6 c3 pin remains keypad column 3 13 gp5 c2 pin becomes gpio pin 5 c2 pin remains keypad column 2 12 gp4 c1 pin becomes gpio pin 4 c1 pin remains keypad column 1 11 gp3 r4 pin becomes gpio pin 3 r4 pin remains keypad row 4 10 gp2 r3 pin becomes gpio pin 2 r3 pin remains keypad row 3 9 gp1 r2 pin becomes gpio pin 1 r2 pin remains keypad row 2 8 gp0 r1 pin becomes gpio pin 0 r1 pin remains keypad row 1 [7:0] [oe7:oe0] gpio pin configured as an output gpio pin configured as an input table 27. gpio control register bit descriptions (write 0x004f/read 0x804f) bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 pu7pu6pu5pu4pu3pu2pu1pu000000000 table 28.gpio pullup disable register (write 0x004e/read 0x804e) bit name description [15:8] [pu7:pu0] 1: p ul l up d i sab l ed . op en col l ector outp ut. 0: pullup enabled. [7:0] 0 reserved: always write as zero. table 29. gpio pullup disable register descriptions bit name description 15 cm4 mask interrupt, status register, and pending register data update on all keys in column 4 14 cm3 mask interrupt, status register, and pending register data update on all keys in column 3 13 cm2 mask interrupt, status register, and pending register data update on all keys in column 2 12 cm1 mask interrupt, status register, and pending register data update on all keys in column 1 [11:0] 0 reserved table 25. keypad column mask register bit descriptions (write 0x0051/read 0x8051)
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 27 read command register name bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 0x8000 x 0000x11x10x9x8x7x6x5x4x3x2x1x0 0x8001 y 0000y11y10y9y8y7y6y5y4y3y2y1y0 0x8002 z1 0000z1_11z1_10z1_9z1_8z1_7z1_6z1_5z1_4z1_3z1_2z1_1z 1_0 0x8003 z1 0000z2_11z2_10z2_9z2_8z2_7z2_6z2_5z2_4z2_3z2_2z2_1z 2_0 0x8005 batt1 0000b1_11b1_10b1_9b1_8b1_7b1_6b1_5b1_4b1_3b1_2b1_1b1_0 0x8006 batt2 0000b2_11b2_10b2_9b2_8b2_7b2_6b2_5b2_4b2_3b2_2b2_1b2_0 0x8007 aux1 0000a1_11a1_10a1_9a1_8a1_7a1_6a1_5a1_4a1_3a1_2a1_1a1_0 0x8008 aux2 0000a2_11a2_10a2_9a2_8a2_7a2_6a2_5a2_4a2_3a2_2a2_1a2_0 0x8009 temp1 0000t1_11t1_10t1_9t1_8t1_7t1_6t1_5t1_4t1_3t1_2t1_1t1_0 0x800a temp2 0000t2_11t2_10t2_9t2_8t2_7t2_6t2_5t2_4t2_3t2_2t2_1t2_0 table 30. analog inputs data register format read command register name bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 0x8004 kpd k15 k14 k13 k12 k11 k10 k9 k8 k7 k6 k5 k4 k3 k2 k1 k0 0x8010 kpdata1 (column m askabl e) k1_15 k1_14 k1_13 k1_12 k1_11 k1_10 k1_9 k1_8 k1_7 k1_6 k1_5 k1_4 k1_3 k1_2 k1_1 k1_0 0x8011 kpdata2 (key m askabl e) k2_15 k2_14 k2_13 k2_12 k2_11 k2_10 k2_9 k2_8 k2_7 k2_6 k2_5 k2_4 k2_3 k2_2 k2_1 k2_0 table 31. keypad data registers bit name description 15 k15 keypad scan result for row 4, column 4. can only be masked by column mask. 14 k14 keypad scan result for row 3, column 4. can only be masked by column mask. 13 k13 keypad scan result for row 2, column 4. can only be masked by column mask. 12 k12 keypad scan result for row 1, column 4. can only be masked by column mask. 11 k11 keypad scan result for row 4, column 3. can only be masked by column mask. 10 k10 keypad scan result for row 3, column 3. can only be masked by column mask. 9 k9 keypad scan result for row 2, column 3. can only be masked by column mask. 8 k8 keypad scan result for row 1, column 3. can only be masked by column mask. 7 k7 keypad scan result for row 4, column 2. can only be masked by column mask. 6 k6 keypad scan result for row 3, column 2. can only be masked by column mask. 5 k5 keypad scan result for row 2, column 2. can only be masked by column mask. 4 k4 keypad scan result for row 1, column 2. can only be masked by column mask. 3 k3 keypad scan result for row 4, column 1. can only be masked by column mask. 2 k2 keypad scan result for row 3, column 1. can only be masked by column mask. 1 k1 keypad scan result for row 2, column 1. can only be masked by column mask. 0 k0 keypad scan result for row 1, column 1. can only be masked by column mask. table 32. keypad data register descriptions
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 28 ______________________________________________________________________________________ bit name description 15 k1_15 keypad scan result for row 4, column 4. can only be masked by column mask. 14 k1_14 keypad scan result for row 3, column 4. can only be masked by column mask. 13 k1_13 keypad scan result for row 2, column 4. can only be masked by column mask. 12 k1_12 keypad scan result for row 1, column 4. can only be masked by column mask. 11 k1_11 keypad scan result for row 4, column 3. can only be masked by column mask. 10 k1_10 keypad scan result for row 3, column 3. can only be masked by column mask. 9 k1_9 keypad scan result for row 2, column 3. can only be masked by column mask. 8 k1_8 keypad scan result for row 1, column 3. can only be masked by column mask. 7 k1_7 keypad scan result for row 4, column 2. can only be masked by column mask. 6 k1_6 keypad scan result for row 3, column 2. can only be masked by column mask. 5 k1_5 keypad scan result for row 2, column 2. can only be masked by column mask. 4 k1_4 keypad scan result for row 1, column 2. can only be masked by column mask. 3 k1_3 keypad scan result for row 4, column 1. can only be masked by column mask. 2 k1_2 keypad scan result for row 3, column 1. can only be masked by column mask. 1 k1_1 keypad scan result for row 2, column 1. can only be masked by column mask. 0 k1_0 keypad scan result for row 1, column 1. can only be masked by column mask. table 33. keypad data register 1 (pending register) descriptions bit name description 15 k2_15 keypad scan result for row 4, column 4. can be masked by key mask or column mask. 14 k2_14 keypad scan result for row 3, column 4. can be masked by key mask or column mask. 13 k2_13 keypad scan result for row 2, column 4. can be masked by key mask or column mask. 12 k2_12 keypad scan result for row 1, column 4. can be masked by key mask or column mask. 11 k2_11 keypad scan result for row 4, column 3. can be masked by key mask or column mask. 10 k2_10 keypad scan result for row 3, column 3. can be masked by key mask or column mask. 9 k2_9 keypad scan result for row 2, column 3. can be masked by key mask or column mask. 8 k2_8 keypad scan result for row 1, column 3. can be masked by key mask or column mask. 7 k2_7 keypad scan result for row 4, column 2. can be masked by key mask or column mask. 6 k2_6 keypad scan result for row 3, column 2. can be masked by key mask or column mask. 5 k2_5 keypad scan result for row 2, column 2. can be masked by key mask or column mask. 4 k2_4 keypad scan result for row 1, column 2. can be masked by key mask or column mask. 3 k2_3 keypad scan result for row 4, column 1. can be masked by key mask or column mask. 2 k2_2 keypad scan result for row 3, column 1. can be masked by key mask or column mask. 1 k2_1 keypad scan result for row 2, column 1. can be masked by key mask or column mask. 0 k2_0 keypad scan result for row 1, column 1. can be masked by key mask or column mask. table 34. keypad data register 2 (status register) descriptions
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 29 dac data register the dac data register stores data that is to be written to the 8-bit dac. table 36 shows the configuration of the dac data register. it is right justified with bit 7?it 0 storing the input data. gpio data register tables 37 and 38 show the format and descriptions for the gpio data register. the register is left justified with data in bit 15?it 8. reading the gpio data register gives the state of the r_ and c_ pins. data written to the gpio data register appears on those r_ and c_ pins, which are configured as general-purpose outputs. data written to pins not configured as general-purpose outputs is not stored. adc transfer function the max1233/max1234 output data is in straight bina- ry format as shown in figure 11. this figure shows the ideal output code for the given input voltage and does not include the effects of offset error, gain error, noise, or nonlinearity. applications information programmable 8-/10-/12-bit resolution the max1233/max1234 provide the option of three dif- ferent resolutions for the adc: 8, 10, or 12 bits. lower resolutions are practical for some measurements such as touch pressure. lower resolution conversions have smaller conversion times and therefore consume less power. program the resolution of the max1233/ max1234 12-bit adcs by writing to the res1 and res0 bits in the adc control register. when the max1233/ max1234 power up, both bits are set to zero so the res- olution is set to 8 bits with a 31? internally timed refer- ence power-up delay as indicated by the adc resolution control table. as explained in the control reg- ister section, the res1 and res0 bits control the refer- component c1 c2 c3 c4 r1 k0 k4 k8 k12 r2 k1 k5 k9 k13 r3 k2 k6 k10 k14 r4 k3 k7 k11 k15 table 35. keypad to key bit mapping bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 00000000da7da6da5da4da3da2da1da0 table 36. dac data register(write 0x000b/read 0x800b) bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 gpd7gpd6gpd5gpd4gpd3gpd2gpd1gpd000000000 table 37. gpio data register (write 0x000f/read 0x800f) bit name description 15...8 gpd7...0 gpio data bits for gpio pins 7...0 7...0 0 reserved table 38. gpio data register bit descriptions (write 0x000f/read 0x800f) output code full-scale transition 11 ... 111 11 ... 110 11 ... 101 00 ... 011 00 ... 010 00 ... 001 00 ... 000 3 0fs fs - 3/2lsb fs = v ref zs = gnd input voltage (lsb) 1lsb = v ref 4096 2 1 max1233 max1234 figure 11. ideal input voltages and output codes
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 30 ______________________________________________________________________________________ ence power-up status when the a/d0?/d3 bits are zero. these values can be set initially on power-up. (subsequently a/d0?/d3 bits are not zero, and any other value of these bits is exclusive to adc resolution programming.) differential ratiometric touch-position measurement the max1233/max1234 provide differential conver- sions. figure 12 shows the switching matrix configura- tion for y coordinate measurement. the +ref and -ref inputs are connected directly to y+ and y-. the conver- sion result is a percentage of the external resistances, and is unaffected by variation in the total touch-screen resistance or the on-resistance of the internal switching matrix. the touch screen remains powered during the acquisition and conversion process. touch-screen settling there are two mechanisms that affect the voltage level at the point where the touch panel is pressed. one is electrical ringing due to parasitic capacitance between the top and bottom layers of the touch screen and the other is the mechanical bouncing caused by vibration of the top layer of the touch screen. thus, the input sig- nal, reference, or both may not settle into their final steady-state values before the adc samples the inputs, and the reference voltage may continue to change dur- ing the conversion cycle. the max1233/max1234 can be programmed to wait for a fixed amount of time after a screen touch has been detected before beginning a scan. use the touch-screen settling control bits in the adc control register (table 11) to set the settling delay to between zero and 100ms. the settling problem is amplified in some applications where external filter capacitors may be required across the touch screen to filter noise that may be generated by the lcd panel or backlight circuitry, etc. the values of these capacitors cause an additional settling time requirement when the panel is touched. any failure to settle before conversion start may show up as a gain error. average the conversion result by writing to the adc control register, as shown in table 10, to minimize noise. touch-pressure measurement the max1233/max1234 provide two methods of mea- surement of the pressure applied to the touch screen. although 8-bit resolution is typically sufficient, the follow- ing calculations use 12-bit resolution demonstrating the maximum precision of the max1233/max1234. figure 13 shows the pressure measurement block diagram. the first method performs pressure measurements using a known x-plate resistance. after completing three conversions, x-position, z1-position, and z2 posi- tion, use the following equation to calculate r touch : the second method requires knowing both the x-plate and y-plate resistance. three touch-screen conver- sions are required in this method as well for measure- ment of the x-position, y-position, and z- position of the touch screen. use the following equation to calculate r touch : r r z x z r y touch xplate position yplate position = ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 11 4096 4096 1 4096 rr xz z touch xplate position = () ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 4096 1 2 1 gnd force line sense line sense line force line +av dd y- x+ y+ +in +ref -ref -in converter figure 12. ratiometric y-coordinate measurement
battery-voltage monitors two dedicated analog inputs (bat1 and bat2) allow the max1233/max1234 to monitor the battery voltages prior to the dc/dc converter. figure 14 shows the battery volt- age monitoring circuitry. the max1233/ max1234 direct- ly monitor battery voltages from 0.5v to 6v. an internal resistor network divides down bat1 and bat2 by 4 so that a 6v battery voltage results in a 1.5v input to the adc. to minimize power consumption, the divider is only enabled during the sampling of bat1 and bat2. figure 15 illustrates the process of battery input reading. max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 31 touch x-position sense line open circuit x+ x- y+ y- force line sense line measure x-position force line v touch z1-resistance open circuit x+ x- y+ y- force line sense line measure z1-resistance force line v v touch z2-resistance open circuit x+ x- y+ y- force line force line measure z2-resistance figure 13. pressure measurement block diagram converter 0.125v to 1.5v 2.5k 7.5k v bat battery 0.5v to 6.0v dc/dc converter 2.7v av dd figure 14. battery measurement block diagram battery input 1 or battery input 2 done no is data averaging done? store battery input 1 or 2 in bat1 or bat2 register power down adc power up adc power up reference convert battery input 1 or 2 power down reference turn off clock host writes adc control register start clock is adc reference in auto power-down mode? no yes set busy low yes set busy high figure 15. battery voltage-reading flowchart
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 32 ______________________________________________________________________________________ auxiliary analog inputs two auxiliary analog inputs (aux1 and aux2) allow the max1233/max1234 to monitor analog input voltages from zero to v ref . figure 16 illustrates the process of auxiliary input reading. temperature measurements the max1233/max1234 provide two temperature mea- surement options: a single-ended conversion method and a differential conversion method. both temperature measurement techniques rely on the semiconductor junction? operational characteristics at a fixed current level. the forward diode voltage (v be ) vs. temperature is a well-defined characteristic. the ambient temperature can be predicted in applications by knowing the value of the v be voltage at a fixed temperature and then moni- toring the delta of that voltage as the temperature changes. figure 17 illustrates the functional block of the internal temperature sensor. the single conversion method requires calibration at a known temperature, but only requires a single reading to predict the ambient temperature. first, the internal diode forward bias voltage is measured by the adc at a known temperature. subsequent diode measurements provide an estimate of the ambient temperature through extrapolation. this assumes a temperature coefficient of -2.1mv/?. the single conversion method results in a resolution of 0.29?/lsb (2.5v reference) and 0.12?/lsb (1.0v reference) with a typical accuracy of ??. figure 18 shows the flowchart for the single tem- perature measurement. the differential conversion method uses two measure- ment points. the first measurement is performed with a fixed bias current into the internal diode. the second measurement is performed with a fixed multiple of the original bias current. the voltage difference between the first and second conversion is proportional to the absolute temperature and is expressed by the following formula: v be = (kt/q) ? ln(n) where: v be = difference in diode voltage n = current ratio of the second measurement to the first measurement k = boltzmann? constant (1.38 10 -23 ev/?elvin) q = electron charge (1.60 10 -19 c) t = temperature in ?elvin the resultant equation solving for ? is: t(?) = q x v / (k ln(n)) auxiliary input 1 or auxiliary input 2 done no is data averaging done? store auxiliary input 1 or 2 in aux1 or aux2 register power down adc power up adc power up reference convert auxiliary input 1 or 2 power down reference turn off clock host writes adc control register start clock is adc reference in auto power-down mode? no yes set busy low yes set busy high figure 16. auxiliary input flowchart temp1 temp2 a/d converter mux figure 17. internal block diagram of temperature sensor
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 33 where: v = v (i n) - v (i1) (in mv) t(?) = 2.68(?/mv) v(mv) t(?) = [2.68(?/mv) v(mv) - 273?]?/ k this differential conversion method does not require a test temperature calibration and can provide much improved absolute temperature measurement. in the differential conversion method, however, the resolution is 1.6?/lsb (2.5v reference) and 0.65?/lsb (1v ref- erence) with a typical accuracy of 3?. figure 19 shows the differential temperature measurement- process. note: the bias current for each diode temperature measurement is only turned on during the acquisition and, therefore, does not noticeably increase power consumption. temperature input 1 done no is data averaging done? store temperature input 1 in temp1 register power down adc power up adc power up reference convert temperature input 1 power down reference turn off clock host writes adc control register start clock is adc reference in auto power-down mode? no yes set busy low yes set busy high figure 18. single temperature measurement process temperature input 1 and temperature input 2 done no is data averaging done? store temperature input 1 in temp1 register power down adc power up adc power up reference convert temperature input 1 power down reference turn off clock host writes adc control register start clock is adc reference in auto power-down mode? no yes set busy low yes set busy high no is data averaging done? store temperature input 2 in temp2 register convert temperature input 2 yes figure 19. differential temperature measurement process
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 34 ______________________________________________________________________________________ battery voltage, auxiliary input, and temperature input scan use this scan to make periodic measurements of both battery inputs, both auxiliary inputs, and both tempera- ture inputs. the respective data registers have the lat- est results at the end of each cycle. thus, a single write by the host to the max1233/max1234 adc control reg- ister results in six different measurements being made. figure 20 shows this scan operation. touch-initiated screen scans (pensts = 1; adsts = 0) in the touch-initiated screen-scan mode, the max1233/max1234 automatically perform a touch- screen scan upon detecting a screen touch. the touch- screen scans performed are determined by the [a/d3:a/d0] written to the adc control register. figure 21 shows the flowchart for a complete touch-initiated x- and y- coordinate scan. selection of resolution, conver- sion rate, averaging, and touch-screen settling time determine the overall conversion time. figure 22 shows the complete flowchart for a touch- initiated x, y, and z scan. table 38 shows adsts bit operation. host-initiated screen scans (pensts = adsts = 0) in this mode, the host processor decides when a touch- screen scan begins. the max1233/max1234 detect a screen touch and drive penirq low. the host recog- nizes the interrupt request and can choose to write to the adc control register to select a touch-screen scan function (pensts = adsts = 0). figures 23 and 24 show the process of a host-initiated screen scan. key-press initiated debounce scan (keysts1 = 1, keysts0 =0) in the key-press initiated debounce mode, the max1233/max1234 automatically perform a debounce upon detecting a key press. key scanning begins once a key press has been detected and ends when a key press has been debounced (figures 25 and 9a). host-initiated debounce scan in this mode, the host processor decides when a debounce scan begins. the max1233/max1234 detect a key press and drive keyirq low. the host processor recognizes the interrupt request and can choose to write to the keypad control register to initiate a debounce scan (figures 26 and 9b). keypad debouncing keys are debounced either when (1) a key press has been detected, or (2) when commanded by the host mpu. the keys scanned by the keypad row and column pins are debounced for a period of time (debounce period) as determined by bits [dbn2:dbn0] of the keypad con- trol register. the keypad controller continues scanning until the keypad stays in the same state for an entire debounce period. keypad data keypad data can be read out of either the keypad data status register (maskable), or the keypad data pending register (not maskable). the keypad mask register is used to mask individual keys in the keypad data status register. gpio control write to bits [gp7:gp0] of the gpio control register to configure one or more of the r_/c_pins as a gpio pin. write to bits [oe7:oe0] of the gpio control register to configure the pins as an input or an output. gpio data can be read from or written to the gpio data register. a read returns the logic state of the gpio pin. a write sets the logic state of a gpio output pin. writing to a gpio input pin has no effect. gpio pullup disable register when programmed as gpio output, by default, the gpio pins are active cmos outputs. write a 1 to the pullup disable register to configure the gpio output as an open-drain output. using the 8-bit dac for lcd/tft contrast control design example: the 8-bit dac offers the ability to control biasing of lcd/tft screens. in the circuit of figure 27, it is desired to have the max1677 dc-dc converter? v out to be adjustable. the minimum and maximum dac voltages (v dac(high) and v dac(low) ) can be found in the electrical characteristics table. the output voltage of the max1677 (v out ) can be cal- culated by noting the following equations: v out = v refdac + i 1 r1 [equation 1] i 1 = i 2 + i 3 [equation 2] i 2 = v refdac / r2 [equation 3] i 3 = (v refdac - v dac ) / r3 [equation 4] substituting equations 2, 3, and 4 into equation 1 yields: v out = v refdac + (r1 / r2) v ref + (r1 / r3) (v refdac - v dac ) [equation 5]
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 35 done no is data averaging done? store battery input 1 in bat1 register power down adc power up adc convert battery input 2 power up reference convert battery input 1 power down reference turn off clock host writes adc control register start clock is adc reference in auto power-down mode? no yes set busy low yes set busy high no is data averaging done? convert temperature input 1 no is data averaging done? convert temperature input 2 no is data averaging done? convert auxiliary input 1 no is data averaging done? store battery input 2 in bat2 register yes store temperature input 1 in temp1 register yes store auxiliary input 1 in aux1 register store temperature input 2 in temp2 register yes yes store auxiliary input 2 in aux2 register yes convert auxiliary input 2 no is data averaging done? battery voltage, auxiliary input, and temperature input scan ([a/d3:a/d0] = 1011) figure 20. scan mode flowchart
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 36 ______________________________________________________________________________________ yes screen touch start clock go to host-initiated scan (figure 23) no yes power up adc yes set penirq low are there unread scan results? no convert x- coordinates is touch-screen settling done? yes no store x- coordinates in x- register is data averaging done? turn on drivers: x+. x- yes no convert y- coordinates is touch-screen settling done? yes no store y- coordinates in y- register is data averaging done? is pensts bit = 1? set busy low turn on drivers: y+, y- done power down adc turn off clock set busy high power up adc reset penirq high penirq-initiated x- and y- screen scan no power down adc figure 21. touch-initiated x- and y- coordinate screen scan
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 37 yes screen touch start clock go to host-initiated scan (figure 24) no yes power up adc yes set penirq low are there unread scan results? no convert x- coordinates is touch-screen settling done? no is data averaging done? turn on drivers: x+, x- yes no power up adc convert y- coordinates is touch-screen settling done? yes no store y- coordinates in y- register power down adc is data averaging done? convert z 1 - coordinates yes no is data averaging done? is pensts bit = 1? set busy low turn on drivers: y+, y- done turn off clock set busy high store z 1 - coordinates in z 1 - register yes no is data averaging done? convert z 2 coordinates store z 2 - coordinates in z 2 - register reset penirq high penirq-initiated x, y, and z screen scan power up adc store x- coordinates in x- register power down adc turn on drivers: y+, x- yes no power up adc is touch-screen settling done? figure 22. touch-initiated x- , y-, and z- coordinate screen scan
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 38 ______________________________________________________________________________________ yes screen touch start clock host writes adc control register (pensts = adsts = 0) no no yes power up adc yes set penirq low are there unread scan results? no convert x- coordinates is touch-screen settling done? no is data averaging done? store x- coordinates in x- register yes no power down adc power up adc turn on drivers: x+, x- convert y- coordinates is touch-screen settling done? yes no is data averaging done? is pensts bit = 1? set busy low turn on drivers: y+, y- done turn off clock set busy high store y- coordinates in y- register reset penirq high host-initiated x- and y- screen scan power down adc go to touch-initiated scan (figure 21) yes figure 23. host-initiated x- and y- coordinate screen scan
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 39 yes screen touch start clock host writes adc control register no no power up adc yes set penirq low are there unread scan results? no convert x- coordinates is touch-screen settling done? yes no store x- coordinates in x- register power down adc is data averaging done? turn on drivers: y+, x- turn on drivers: x+, x- yes no power up adc convert y- coordinates is touch-screen settling done? yes no store y- coordinates in y- register power down adc is data averaging done? yes no power up adc convert z 1 - coordinates is touch-screen settling done? yes no is data averaging done? is pensts bit = 1? set busy low turn on drivers: y+, y- done turn off clock set busy high store z 1 - coordinates in z 1 - register yes no is data averaging done? convert z 2 - coordinates store z 2 - coordinates iin z 2 - register reset penirq high host-initiated x-, y-, and z- screen scan power down adc go to touch-initiated scan (figure 22) yes figure 24. host-initiated x-, y-, and z- coordinate screen scan
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 40 ______________________________________________________________________________________ yes keypad touch start clock go to host-initiated debounce scan no yes set keyirq low are there unread debounce results? is keysts1 = 1? set busy low scan and debounce keys done store keypad scan results in register reset keyirq high set busy high key-press-initiated debounce scan no figure 25. key-press-initiated debounce scan yes keypad touch start clock go to key-press-initiated debounce scan no no host writes adc control register set keyirq low are there unread debounce results? is keysts1 = 1? set busy low scan and debounce keys done store keypad scan results in register reset keyirq high set busy high host-initiated debounce scan yes figure 26. host-initiated debounce scan
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 41 equation 5 shows that the maximum output voltage occurs for the minimum dac voltage, and that the minimum output voltage occurs for the maximum dac voltage. to ensure that the desired output swing is achieved, choose appropriate values of r1, r2, and r3. calculate v outmax using the following equation: v outmax = v refmax + (r1 max / r2 min )v refmax + (r1 max / r3 min ) (v refmax - v dacmin ) [equation 6] if v outmax exceeds the maximum ratings of the lcd/tft display, the dac codes that cause the output voltage to go too high must be avoided. calculate v outmin using the following equation: v outmin = v refmin + (r1 min / r2 max )v refmin + (r1 max / r3 min ) (v refmin - v dacmax ) [equation 7] if v outmin is too low for desired operation, avoid the dac codes, which cause the output voltage to go too low. connection to standard interface spi and microwire interfaces when using an spi interface (figure 28a) or microwire (figure 28b), set the cpol = cpha = 0. at least four 8-bit operations are necessary to read or write data to/from the max1233/max1234. dout data transitions on the serial clock? falling edge and is clocked into the ? on the sclk? rising edge. the first max1233 max1234 r1 r3 i 1 i 2 i 3 r2 av dd dac dacout feedback resistors v ref 1.25v error amp simplified dc/dc converter v batt v out (lcd bias) control max1677 figure 27. lcd contrast control circuit max1233 max1234 cs sck miso mosi cs sclk dout din spi ss v dd busy penirq keyirq figure 28a. spi interface max1233 max1234 cs sck miso mosi cs sclk dout din microwire busy penirq keyirq figure 28b. microwire interface
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller 42 ______________________________________________________________________________________ two 8-bit data streams write the command word into the max1233/max1234. the next two 8-bit data streams can contain either the input or output data. qspi interface using the high-speed qspi interface (figure 29) with cpol = 0 and cpha = 0, the max1233/max1234 sup- port a maximum f sclk of 10mhz. dout data transi- tions on the serial clock? falling edge and is clocked into the ? on the sclk? rising edge. layout, grounding, and bypassing for best performance, use printed circuit boards with good layouts; do not use wire-wrap boards even for prototyping. ensure that digital and analog signal lines are separated from each other. do not run analog and digital (especially clock) lines parallel to one another, or digital lines underneath the adc package. figure 30 shows the recommended system ground connections. establish a single-point analog ground (star ground point) at gnd. connect all analog grounds to the star ground. connect the digital system ground to the star ground at this point only. for lowest noise oper- ation, the ground return to the star ground? power supply should be low impedance and as short as possible. high-frequency noise in the power supply may affect the high-speed comparator in the adc. bypass the supply to the star ground with a 0.1? capacitor as close to pins 1 and 2 of the max1233/max1234 as possible. minimize capacitor lead lengths for best sup- ply-noise rejection. if the power supply is very noisy, a 10 resistor can be connected as a lowpass filter. while using the max1233/max1234 with a resistive touch screen, the interconnection between the convert- er and the touch screen should be as short and robust as possible. since resistive touch screens have a low resistance, longer or loose connections are a source of error. noise can also be a major source of error in touch-screen applications (e.g., applications that require a backlight lcd panel). this emi noise can be coupled through the lcd panel to the touch screen and cause ?lickering?of the converted data. utilizing a touch screen with a bottom-side metal layer connected to ground couples the majority of noise to ground. in addition, the filter capacitors from y+, y-, x+, and x- inputs to ground also help reduce the noise further. caution should be observed for settling time of the touch screen. definitions integral nonlinearity integral nonlinearity (inl) is the deviation of the values on an actual transfer function from a straight line. this straight line can be either a best-straight-line fit or a line drawn between the end points of the transfer function, once offset and gain errors have been nullified. the static linearity parameters for the max1233/max1234 are measured using the end-point method. differential nonlinearity differential nonlinearity (dnl) is the difference between an actual step width and the ideal value of 1lsb. a dnl error specification of less than 1lsb guarantees no missing codes and a monotonic transfer function. aperture jitter aperture jitter (t aj ) is the sample-to-sample variation in the time between the samples. aperture delay aperture delay (t ad ) is the time defined between the falling edge of the sampling clock and the instant when an actual sample is taken. max1233 max1234 cs sck miso mosi cs sclk dout din qspi ss v dd busy penirq keyirq figure 29. qspi interface +3v/+5v +3v/+5v gnd supplies dgnd v dd dv dd gnd av dd digital circuitry *optional max1233 max1234 r* = 10 figure 30. power-supply grounding connection
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller ______________________________________________________________________________________ 43 signal-to-noise ratio for a waveform perfectly reconstructed from digital sam- ples, signal-to-noise ratio (snr) is the ratio of full-scale analog input (rms value) to the rms quantization error (residual error). the ideal, theoretical minimum analog- to-digital noise is caused by quantization error only and results directly from the adc? resolution (n bits): snr = (6.02 ? n + 1.76) db in reality, there are other noise sources besides quanti- zation noise: thermal noise, reference noise, clock jitter, etc. snr is computed by taking the ratio of the rms signal to the rms noise, which includes all spectral components minus the fundamental, the first five har- monics, and the dc offset. signal-to-noise plus distortion signal-to-noise plus distortion (sinad) is the ratio of the fundamental input frequency? rms amplitude to the rms equivalent of all other adc output signals: sinad (db) = 20 ? log (signal rms / noise rms ) effective number of bits effective number of bits (enob) indicates the global accuracy of an adc at a specific input frequency and sampling rate. an ideal adc? error consists of quantization noise only. with an input range equal to the full-scale range of the adc, calculate the effective number of bits as follows: enob = (sinad - 1.76) / 6.02 total harmonic distortion total harmonic distortion (thd) is the ratio of the rms sum of the first five harmonics of the input signal to the fundamental itself. this is expressed as: where v 1 is the fundamental amplitude, and v 2 through v 5 are the amplitudes of the 2nd- through 5th-order harmonics, respectively. spurious-free dynamic range spurious-free dynamic range (sfdr) is the ratio of rms amplitude of the fundamental (maximum signal compo- nent) to the rms value of the next-largest distortion component. thd vvvv v = +++ ? ? ? ? ? ? ? ? 20 2 2 3 2 4 2 5 2 1 2 log chip information transistor count: 28,629 package information for the latest package outline information, go to www.maxim-ic.com/packages . package type package code document no. 28 qfn g2855-2 21-0091 28 tqfn t2855-6 21-0140
max1233/max1234 15kv esd-protected touch-screen controllers include dac and keypad controller maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 44 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2008 maxim integrated products is a registered trademark of maxim integrated products. revision history revision number revision date description pages changed 0 7/02 initial release 43/08 added register address information. fixed dclk typo. fixed cs timing dependency. 12, 18?7, 29, 41, 42

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