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19-2512; Rev 1; 9/03
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
General Description
The MAX1233/MAX1234 are complete PDA controllers in a 5mm x 5mm, 28-pin QFN package. They feature 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, 2C accurate, on-chip temperature sensor, direct +6V battery monitor, 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 TransZorbTM 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. Softwareconfigurable scan control and internal timers give the user flexibility without burdening the host processor. These devices consume only 260A at the maximum sampling rate of 50ksps. Supply current falls to below 50A for sampling rates of 10ksps. The MAX1233/MAX1234 are guaranteed over the -40C to +85C temperature range.
KIT ATION EVALU ABLE AVAIL
Features
o ESD-Protected Analog Inputs 15kV IEC 1000-4-2 Air-Gap Discharge 8kV IEC 1000-4-2 Contact Discharge o Single-Supply Operation +2.7V to +3.6V (MAX1233) +4.75V to +5.25V (MAX1234) o 4-Wire Touch-Screen Interface o Internal +1.0V/+2.5V Reference or External Reference (+1.0V to AVDD) o SPITM/QSPITM/MICROWIRETM-Compatible 10MHz Serial Interface o 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 o 8-Bit DAC for LCD Bias Control o 4 x 4 Keypad Programmable Controller Offers Up to Eight GPIO Pins o Automatic Detection of Screen Touch, Key Press, and End of Conversion o Programmable 8-, 10-, 12-Bit Resolution o Programmable Conversion Rates o AutoShutdownTM Between Conversions o Low Power 260A at 50ksps 50A at 10ksps 6A at 1ksps 0.3A Shutdown Current o 28-Pin 5mm x 5mm QFN Package
MAX1233/MAX1234
Applications
Personal Digital Assistants Pagers Touch-Screen Monitors Cellular Phones MP3 Players Portable Instruments Point-of-Sale Terminals
Pin Configuration
PENIRQ
SCLK
28
CS
27
26
25
24
DOUT
BUSY
TOP VIEW
23
22
KEYIRQ
DIN
DVDD AVDD *X+ *Y+ *X*YGND
1 2 3 4 5 6 7 10 11 12 13 14 8 9
21 20 19
C4 C3 C2 C1 R1 R2 R3
Ordering Information
PART MAX1233EGI MAX1234EGI TEMP RANGE -40C to +85C -40C to +85C PIN-PACKAGE 28 QFN (5mm x 5mm) 28 QFN (5mm x 5mm)
MAX1233 MAX1234
18 17 16 15
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. 1
DACOUT
*AUX1
*BAT1
*BAT2
*AUX2
QFN
*PIN INCLUDES 8kV/15kV ESD PROTECTION.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
REF
R4
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
ABSOLUTE MAXIMUM RATINGS
AVDD to GND............................................................-0.3V to +6V DVDD to AVDD .......................................................-0.3V to +0.3V Digital Inputs/Outputs to GND .................-0.3V to (DVDD + 0.3V) X+, Y+, X-, Y-, AUX1, AUX2, and REF to GND ..................................-0.3V to (AVDD + 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 (TA = +70C) 28-Pin QFN (derate 28.5mW/C above +70C) .................2W Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-60C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER DC ACCURACY (Note 1) Resolution No Missing Codes Relative Accuracy (Note 2) Differential Nonlinearity Offset Error INL DNL 12-bit mode 10-bit and 8-bit modes 12-bit mode 10-bit and 8-bit modes 12-bit mode 10-bit and 8-bit modes 12-bit mode Gain Error (Note 3) 10-bit mode 8-bit mode Total Unadjusted Error Offset Temperature Coefficient Gain Temperature Coefficient Channel-to-Channel Offset Channel-to-Channel Gain Matching Noise Including internal VREF Full-scale input MAX1233 AVDD = DVDD = +2.7V to +3.6V MAX1234 AVDD = DVDD = +5V 5% TUE 12-bit mode 10-bit and 8-bit modes Software-programmable 8/10/12 bit 11 0.8 0.5 0.8 0.5 0.5 0.5 0.5 0.5 0.5 2 1 0.4 0.4 0.1 0.1 50 0.4 mV 0.3 LSB ppm/C ppm/C LSB LSB VRMS 4 LSB 4 2 2 12 Bits Bits LSB LSB LSB SYMBOL CONDITIONS ANALOG-TO-DIGITAL CONVERTER MIN TYP MAX UNITS
Power-Supply Rejection
PSR
DYNAMIC SPECIFICATIONS (1kHz SINE WAVE, VIN = 2.5VP-P FOR MAX1233, VIN = 4.096VP-P FOR MAX1234, 50ksps, fSCLK = 10MHz) Signal-to-Noise Plus Distortion SINAD 69 dB
2
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Total Harmonic Distortion Spurious-Free Dynamic Range Full-Power Bandwidth Full-Linear Bandwidth CONVERSION RATE Internal Oscillator Frequency Aperture Delay Aperture Jitter Maximum Serial Clock Frequency Duty Cycle AUXILIARY ANALOG INPUTS (AUX1, AUX2) Input Voltage Range Input Leakage Current Input Capacitance BATTERY MONITOR INPUTS (BAT1, BAT2) Input Voltage Range Input Impedance Accuracy TEMPERATURE MEASUREMENT Temperature Range Resolution Accuracy INTERNAL ADC REFERENCE Reference Output Voltage Output Tempco Reference Output Impedance Reference Short-Circuit Current EXTERNAL ADC REFERENCE (INTERNAL REFERENCE DISABLED, REFERENCE APPLIED TO REF) Reference Input Voltage Range Input Impedance Input Current (Note 6) CS = GND or VDD VREF = +2.5V at 50ksps (MAX1233) VREF = +4.096V at 50ksps (MAX1234) Shutdown/between conversions 1.0 1 5 8 0.1 10 15 A VDD V G VREF TCVREF Normal operation 2.5V mode, TA = +25C 1.0V mode, TA = +25C 2.470 0.980 2.500 1.000 60 250 18 2.530 1.020 ppm/C mA V Differential method (Note 4) Single measurement method (Note 5) Differential method (Note 4) Single measurement method (Note 5) -40 1.6 0.3 3 2 +85 C C C Sampling battery Battery monitor OFF Internal reference -3 0.5 10 1 +3 6.0 V k G % Channel not selected or conversion stopped 0 0.1 34 VREF 1 V A pF fSCLK 10 30 70 8 30 <50 11.5 MHz ns ps MHz % SYMBOL THD SFDR -3dB point SINAD > 67dB CONDITIONS MIN TYP -84 84 0.5 50 MAX UNITS dB dB MHz kHz
MAX1233/MAX1234
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
ELECTRICAL CHARACTERISTICS (continued)
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER DC ACCURACY Resolution Integral Linearity Error Differential Linearity Error Offset Error Offset Error Temperature Coefficient Full-Scale Error Full-Scale Error Temperature Coefficient DYNAMIC PERFORMANCE Voltage Output Slew Rate Output Settling Time Glitch Impulse Wake-Up Time DAC OUTPUT Internal DAC Reference Output Load Regulation Output Resistance VREFDAC (Note 10) Code = 255; 0 to 100A Code = 0; 0 to 100A Power-down mode TOUCH-SCREEN CONTROLLER On-Resistance Touch-Detection Internal Pullup Resistance Pullup Resistance Pulldown Resistance DIGITAL INPUTS (SCLK, CS, DIN, R_, C_) Input Voltage Low Input Voltage High Input Leakage Current VIL VIH IL 0.7 DVDD 0.1 1 0.3 DVDD V V A Y+, X+ Y-, XX+ to AVDD KEYPAD CONTROLLER C4, C3, C2, C1 (Note 11) R4, R3, R2, R1 (Note 11) DIGITAL INTERFACE 0.5 16 k k 7 9 1 M 0.85 AVDD 0.9 AVDD 0.5 0.5 1.0 0.95 AVDD V LSB M Positive and negative 0.5LSB; 50k and 50pF load (Note 9) Code 127 to 128 From shutdown 0.4 20 40 50 V/s s nV/s s Code = 255, no load Code = 255, no load 10 INL DNL VOS (Note 7) No missing codes (Note 8) 1 1 5 SYMBOL CONDITIONS DIGITAL-TO-ANALOG CONVERTER 8 1.0 1.0 25 Bits LSB LSB mV ppm/C % ppm/C MIN TYP MAX UNITS
4
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.)
PARAMETER Input Capacitance DIGITAL OUTPUT (DOUT) Output Voltage Low Output Voltage High VOL VOH ISINK = 2mA ISINK = 4mA ISOURCE = 1.5mA DVDD 0.5 0.4 DVDD 0.5 2.7 4.75 3 5 0.5 150 150 670 100 40 40 40 0 CLOAD = 50pF CLOAD = 50pF CLOAD = 50pF 40 0 CLOAD = 50pF (Note 13) 40 230 40 45 40 3.6 5.25 5 500 230 900 ns ns ns ns ns ns ns ns ns ns ns ns A 0.4 0.8 V V SYMBOL CIN CONDITIONS MIN TYP 15 MAX UNITS pF
MAX1233/MAX1234
DIGITAL OUTPUT (BUSY, PENIRQ, KEYIRQ, R_, C_) Output Voltage Low Output Voltage High VOL VOH ISINK = 0.2mA ISOURCE = 0.2mA POWER REQUIREMENTS Supply Voltage (Note 12) AVDD / DVDD IAVDD + IDVDD MAX1233 MAX1234 Idle; all blocks shut down Analog and Digital Supply Current TIMING CHARACTERISTICS SCLK Clock Period SCLK Pulse Width High SCLK Pulse Width Low DIN to SCLK Rise Setup SCLK Rise to DIN Hold SCLK Fall to DOUT Valid CS Fall to DOUT Enabled CS Rise to DOUT Disabled CS Fall to SCLK Rise CS Fall to SCLK Ignored SCLK Rise to R_/C_ Data Valid CS Pulse Width High tCP tCH tCL tDS tDH tDOV tDV tDOD tCSS tCSH tGPO tCSW Only ADC on; fSAMPLE = 20ksps Only DAC on; no load Only internal reference on V V V
Note 1: Tested at DVDD = AVDD = +2.7V (MAX1233), DVDD = AVDD = +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 K = (VTEMP2 - VTEMP1) x 2680K/V. No calibration is necessary. Note 5: Temperature coefficient is -2.1mV/C. Determine absolute temperature by extrapolating from a calibrated value. Note 6: ADC performance is limited by the conversion noise floor, typically 300VP-P. An external reference below 2.5V can compromise the ADC performance. Note 7: Guaranteed from code 5 to 255.
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
ELECTRICAL CHARACTERISTICS (continued)
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V (MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1F capacitor at REF, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) Note 8: Note 9: Note 10: Note 11: Note 12: Note 13: The offset value extrapolated from the range over which the INL is guaranteed. Output settling time is measured by stepping from code 5 to 255, and from code 255 to 5. Actual output voltage at full scale is 255/256 x VREFDAC. Resistance is open when configured as GPIO or in shutdown. AVDD and DVDD should not differ by more than 300mV. When configured as GPIO.
Timing Diagram
CS tCSW tCSS tCL tCH tCP tCSH tCSH tCSS
SCLK tDH tDS
DIN tDOV tDV DOUT tDOD
R_/C_
NOTE: TIMING NOT TO SCALE.
tGPO
6
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
Typical Operating Characteristics
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.)
SHUTDOWN CURRENT vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc01
MAX1233/MAX1234
SHUTDOWN CURRENT vs. TEMPERATURE
MAX1233/34 toc02
INTERNAL OSCILLATOR FREQUENCY vs. ANALOG SUPPLY VOLTAGE
INTERNAL OSCILLATOR FREQUENCY (MHz) 9.8 9.6 9.4 9.2 9.0 8.8 8.6 8.4 8.2 8.0 2.7 3.2 3.7 MAX1233/MAX1234
MAX1233/34 toc03
300 250 SHUTDOWN CURRENT (nA) 200 150 100 50 0 2.7 3.2 3.7 4.2 4.7 5.2 AVDD (V)
300 250 SHUTDOWN CURRENT (nA) 200 150 100 50 0 -40 -20 0 20 40 60 80 TEMPERATURE (C)
10.0
4.2
4.7
5.2
AVDD (V)
INTERNAL OSCILLATOR FREQUENCY vs. TEMPERATURE
MAX1233/34 toc04
TEMP1 DIODE VOLTAGE vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc05
TEMP1 DIODE VOLTAGE vs. TEMPERATURE
0.75 TEMP1 DIODE VOLTAGE (V) 0.70 0.65 0.60 0.55 0.50 0.45 0.40
MAX1233/34 toc06
9.8 INTERNAL OSCILLATOR FREQUENCY (MHz) 9.6 9.4 9.2 9.0 8.8 8.6 -40 -20 0 20 40 60 80 TEMPERATURE (C) MAX1233, AVDD = +3.0V MAX1234, AVDD = +5.0V
0.70 0.68 TEMP1 DIODE VOLTAGE (V) 0.66 0.64 0.62 0.60 0.58 0.56 0.54 0.52 0.50 2.7 3.2 3.7 4.2 4.7
0.80
5.2
-40 -25 -10
5
20
35
50
65
80
AVDD (V)
TEMPERATURE (C)
TEMP2 DIODE VOLTAGE vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc07
TEMP2 DIODE VOLTAGE vs. TEMPERATURE
MAX1233/34 toc08
0.80
0.90 0.85 TEMP2 DIODE VOLTAGE (V) 0.80 0.75 0.70 0.65
TEMP2 DIODE VOLTAGE (V)
0.75
0.70
0.65
0.60 2.7 3.2 3.7 4.2 4.7 5.2 AVDD (V)
0.60 -40 -25 -10 5 20 35 50 65 80 TEMPERATURE (C)
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Typical Operating Characteristics (continued)
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.)
ADC INTEGRAL NONLINEARITY vs. OUTPUT CODE
MAX1233/34 toc09
ADC DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE
0.8 0.6 0.4 DNL (LSB) 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0
MAX1233/34 toc10
1.0 0.8 0.6 0.4 INL (LSB) 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 0 500 1000 1500 2000 2500 3000 3500 4000 OUTPUT CODE
1.0
0
500 1000 1500 2000 2500 3000 3500 4000 OUTPUT CODE
ADC OFFSET ERROR vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc11
ADC OFFSET ERROR vs. TEMPERATURE
1.5 OFFSET ERROR (LSB) 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0
MAX1233/34 toc12
2.0 1.5 OFFSET ERROR (LSB) 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0 2.7 3.2 3.7 4.2 4.7
2.0
5.2
-40
-20
0
20
40
60
80
AVDD (V)
TEMPERATURE (C)
ADC GAIN ERROR vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc13
ADC GAIN ERROR vs. TEMPERATURE
1.5 1.0 GAIN ERROR (LSB) 0.5 0 -0.5 -1.0 -1.5 -2.0 -40 -20 0 20 40 60 80
MAX1233/34 toc14
2.0 1.5 1.0 GAIN ERROR (LSB) 0.5 0 -0.5 -1.0 -1.5 -2.0 2.7 3.2 3.7 4.2 4.7 5.2 AVDD (V)
2.0
TEMPERATURE (C)
8
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Typical Operating Characteristics (continued)
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.)
ADC EXTERNAL REFERENCE INPUT CURRENT vs. SAMPLING RATE
MAX1233 VREF = +2.5V REFERENCE CURRENT (A) 6
MAX1233/34 toc15
ADC SUPPLY CURRENT vs. SAMPLING RATE
MAX1233/34 toc16
8
1000
SUPPLY CURRENT (A)
100
4
10
2
1
0 100 1k fSAMPLE (Hz) 10k 100k
0.1 1 10 100 1k 10k 100k fSAMPLE (Hz)
ADC SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1233/34 toc17
ADC SUPPLY CURRENT vs. TEMPERATURE
AVDD = +3V 120 SUPPLY CURRENT (A) 100 80 60 40 20 0
MAX1233/34 toc18
250 EXTERNAL REF fSAMPLE = 20ksps 200 SUPPLY CURRENT (A)
140
150
100
50
0 2.7 3.2 3.7 4.2 4.7 5.2 AVDD (V)
-40
-20
0
20
40
60
80
TEMPERATURE (C)
DAC INTEGRAL NONLINEARITY vs. CODE
MAX1233/34 toc19
DAC DIFFERENTIAL NONLINEARITY vs. OUTPUT CODE
MAX1233/34 toc20
0.075 0.050 0.025 INL (LSB) 0 -0.025 -0.050 -0.075 -0.100 0 50 100 150 CODE 200 250
0.075 0.050 0.025 DNL (LSB) 0 -0.025 -0.500 -0.075 -0.100
300
0
50
100
150
200
250
300
OUTPUT CODE
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Typical Operating Characteristics (continued)
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.)
DAC FULL-SCALE ERROR vs. ANALOG SUPPLY VOLTAGE
0.75 0.50 FULL-SCALE ERROR (LSB) 0.25 0 -0.25 -0.50 -0.75 2.5 3.0 3.5 4.0 AVDD (V) 4.5 5.0
MAX1233/34 toc21
DAC FULL-SCALE ERROR vs. TEMPERATURE
1.2 0.8 FULL-SCALE ERROR (LSB) FULL-SCALE ERROR (%) 0.4 0 -0.4 -0.8 -1.2 5.5 0.75 0.50 0.25 0 -0.25 -0.50 -0.75 -40 -20 0 20 40 60 80 TEMPERATURE (C)
MAX1233/34 toc22
1.2 0.8 0.4 0 -0.4 -0.8 -1.2 FULL-SCALE ERROR (%) VREF (V)
DAC SUPPLY CURRENT vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc23
DAC SUPPLY CURRENT vs. TEMPERATURE
175 DAC SUPPLY CURRENT (A) 150 125 100 75 50 25
MAX1233/34 toc24
250
200
DAC SUPPLY CURRENT (A)
200
150
100
50
0 2.7 3.2 3.7 4.2 4.7 5.2 AVDD (V)
0 -40 -20 0 20 40 60 80 TEMPERATURE (C)
ADC REFERENCE VOLTAGE vs. ANALOG SUPPLY VOLTAGE
2.550
MAX1233/34 toc25
ADC REFERENCE VOLTAGE vs. TEMPERATURE
1.020 2.60
MAX1233/34 toc26
1.250
2.525 VREF (V) VREF = 1.0V 2.500 VREF = 2.5V 2.475
1.010 VREF (V) VREF (V)
2.55 VREF = 1.0V
1.125
1.000
2.50
1.000
0.990
2.45
VREF = 2.5V
0.875
2.450 2.7 3.2 3.7 4.2 4.7 5.2 AVDD (V)
0.980
2.40 -40
0.750 -20 0 20 40 60 80 TEMPERATURE (C)
10
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Typical Operating Characteristics (continued)
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK = 10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1F capacitor at REF, TA = +25C, unless otherwise noted.) ADC REFERENCE SUPPLY CURRENT vs. ANALOG SUPPLY VOLTAGE
MAX1233/34 toc27
REFERENCE SUPPLY CURRENT vs. TEMPERATURE
MAX1233/34 toc28
750
750
SUPPLY CURRENT (A)
650
SUPPLY CURRENT (A)
700
700
650
600
600
550 2.7 3.2 3.7 4.2 4.7 5.2 AVDD (V)
550 -40 -25 -10 5 20 35 50 TEMPERATURE (C) 65 80
Pin Description
PIN 1 2 3* 4* 5* 6* 7 8* 9* 10* 11* NAME DVDD AVDD X+ Y+ XYGND BAT1 BAT2 AUX1 AUX2 FUNCTION Positive Digital Supply Voltage, +2.7V to +3.6V for MAX1233, +4.75V to +5.25V for MAX1234. Bypass with a 0.1F capacitor. Must be within 300mV of AVDD. Positive Analog Supply Voltage, +2.7V to +3.6V for MAX1233, +4.75V to +5.25V for MAX1234. Bypass with a 0.1F capacitor. Must be within 300mV of DVDD. X+ Position Input Y+ Position Input X- Position Input Y- Position Input Analog and Digital Ground Battery Monitoring Input 1. Measures battery voltages up to 6V. Battery Monitoring Input 2. Measures battery voltages up to 6V. Auxiliary Analog Input 1 to ADC. Measures analog voltages from zero to VREF. Auxiliary Analog Input 2 to ADC. Measures analog voltages from zero to VREF. 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 AVDD. Bypass REF to GND with a 0.1F capacitor in the external reference mode only. DAC Voltage Output; 0.9 x AVDD Full Scale Keypad Row 4. Can be reconfigured as GPIO3. Keypad Row 3. Can be reconfigured as GPIO2. Keypad Row 2. Can be reconfigured as GPIO1. Keypad Row 1. Can be reconfigured as GPIO0. Keypad Column 1. Can be reconfigured as GPIO4.
12
REF
13 14 15 16 17 18
DACOUT R4 R3 R2 R1 C1
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Pin Description (continued)
PIN 19 20 21 22 23 24 25 26 27 28 NAME C2 C3 C4 KEYIRQ PENIRQ DOUT BUSY DIN SCLK CS FUNCTION Keypad Column 2. Can be reconfigured as GPIO5. Keypad Column 3. Can be reconfigured as GPIO6. Keypad Column 4. Can be reconfigured as GPIO7. Active-Low Keypad Interrupt. KEYIRQ is low when a key press is detected. Active-Low Pen Touch Interrupt. PENIRQ is low when a screen touch is detected. Serial Data Output. Data is clocked out at SCLK falling edge. High impedance when CS is high. 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. Serial Data Input. Data is clocked in on the rising edge of 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%). Active-Low Chip Select. Data is not clocked into DIN unless CS is low. When CS is high, DOUT is high impedance.
*ESD protected: 8kV Contact, 15kV Air.
Detailed Description
The MAX1233/MAX1234 are 4-wire touch-screen controllers. Figure 1 shows the functional diagram of the MAX1233/MAX1234. Each device includes a 12-bit sampling 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 onresistance 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.
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 converter 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's analog input section including the input multiplexer, the differential input, and the differential reference. The input multiplexer 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's source impedance is high, the acquisition time lengthens, and more time must be allowed. The acquisition time (tACQ) is the maximum time the device takes to acquire the input signal to 12bit accuracy. Configure tACQ by writing to the ADC control register. See Table 1 for the maximum input signal source impedance (RSOURCE) for complete settling during acquisition. Accommodate higher source impedances by placing a 0.1F capacitor between the analog input and GND. Input Bandwidth The ADC's input-tracking circuitry has a 0.5MHz smallsignal bandwidth. To avoid high-frequency signals being aliased into the frequency band of interest, antialias filtering is recommended.
Touch-Screen Operation
The 4-wire touch-screen controller works by creating a voltage gradient across the vertical or horizontal resistive 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 internal MOSFET switches that connect each resistive layer to AVDD 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 AVDD and the other side to ground. The horizontal resistive layer functions as a sense line. One side of this resistive layer gets connected to the X+ input, while the other side is left
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
C1 C2 C3 C4 R1 R2 R3 R4
OSCILLATOR
KEYPAD CONTROLLER AND GPIO
MAX1233 MAX1234
REGISTERS AND SCAN STATE CONTROL TEMP SENSOR
*X+ *XX/Y SWITCHES *Y+ *YMUX 12-BIT ADC BATTERY MONITOR BATTERY MONITOR SERIAL DATA I/O
DOUT SCLK DIN CS PENIRQ KEYIRQ
*BAT1
BUSY
*BAT2 *AUX1 *AUX2 REF
INTERNAL REFERENCE 2.5V/1.0V 8-BIT DAC
DACOUT
REF DAC
*ESD PROTECTED
Figure 1. Block Diagram
+AVDD
Table 1. Maximum Input Source Impedance
ACQUISITION RESOLUTION TIME (s) (BITS) 1.5 1.5 8 10 12 8 10 12 8 10 12 MAXIMUM RSOURCE FOR COMPLETE SETTLING DURING ACQUISITION (k) 2.6 2.0 1.5 23 19 15 560 470 400
FORCE LINE Y+
SENSE LINE X+
+IN -IN SENSE LINE
+REF -REF
1.5 5.0 5.0 5.0 95 95 95
FORCE LINE
Y-
GND
Figure 2. Touch-Screen Measurement
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
+AVDD VREF
TEMP2
TEMP1
MAX1233 MAX1234
X+
XREF ON/OFF
Y+ Y+IN
+REF CONVERTER -IN 2.5V/1.0V REFERENCE -REF
7.5k VBAT1 7.5k VBAT2 2.5k 2.5k
BATTERY ON AUX1 AUX2 GND
BATTERY ON
Figure 3. Simplified Diagram of Analog Input Section
Analog Input Protection Internal protection diodes that clamp the analog input to AVDD 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 AVDD 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 8kV, using the Contact-Discharge method and 15kV using the Air-Gap method specified in IEC1000-4-2.
Reference for ADC
Internal Reference The MAX1233/MAX1234 offer an internal voltage reference 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
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
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 reference 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 powered up and the internal ADC reference is always ON. The MAX1233/MAX1234 internal reference remains fully powered after completing a scan.
+1.25V BANDGAP 3R 2x REF PIN OPTIONAL
2R
Figure 4. Block Diagram of the Internal Reference
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 reference connected to REF for ADC conversion. External Reference The MAX1233/MAX1234 can accept an external reference 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 15A 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 0.1F capacitor. Selecting Internal or External Reference Set the type of reference being used by programming the ADC control register. To select the internal reference, 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.
Internal Clock
The MAX1233/MAX1234 operate from an internal oscillator, which is accurate to within 20% of the 10MHz specified clock rate. The internal oscillator controls the timing of the acquisition, conversion, touch-screen settling, 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 150A (typ) and provides 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's output is pulled to ground with a 1M load. The internal DAC can be used in various system applications 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 converter (V/I) that generates a reference current. This current is mirrored to 255 equally weighted current sources. DAC switches control the outputs of these current 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 = (VREF/256). The DAC has a full-scale output voltage of (0.9 x AVDD - 1LSB).
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-
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
+AVDD VREF 1M SW1 SW2 SW255 S1 TOUCH-SCREEN DETECTOR X+ PENIRQ
OUT
TOUCH SCREEN
Y+
Figure 5. DAC Current-Steering Topology
Output Buffer The DAC voltage output is an internally buffered unitygain follower that slews at up to 0.4V/s. 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 5s when loaded with 10k in parallel 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.
XY-
S2
Figure 6. Touch-Screen Detection Block Diagram
Keypad Controller and GPIO
The keypad controller is designed to interface a matrixtype 4 rows x 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 masking 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 holds all keypad scan results, including masked data, and is thus the pending register. 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.
internally pulled to AVDD 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 0.1s 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 DVDD and the R_ pins are internally pulled to GND through a 16k resistor. When a key is pressed, the associated row pin is pulled to DVDD and the key press is detected. Figure 7 shows the key-press detection circuitry.
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
Interrupts
PEN Interrupt Request (PENIRQ) The PENIRQ output can be used to alert the host controller of a screen touch. The PENIRQ output is normally
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
SIMPLIFIED KEYPAD CIRCUITRY
DRIVERS PULL HIGH OR GO THREE-STATE
C1 R1
C2
C3
C4
TO KEYPAD WAKEUP AND DEBOUNCE LOGIC
KEYPAD R2
R3
R4
Figure 7. Key-Press Detection Circuitry
X+
X+
PENIRQ
PENIRQ
BUSY
BUSY
CS DATA READ
CS DATA READ DOUT TOUCHSCREEN DATA
DIN DOUT
TOUCHSCREEN DATA
Figure 8a. Timing Diagram for Touch-Initiated Screen Scan
Figure 8b. Timing Diagram for Host-Initiated Screen Scan 17
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
high and goes low after a screen touch is detected. 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 controller 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.
R_
KEYIRQ
BUSY
CS DATA READ DOUT
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.
TOUCHSCREEN DATA
Figure 9a. Timing Diagram for Key-Press-Initiated Debounce Scan
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. 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 interface. 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
R_ KEYIRQ
BUSY
CS
DATA READ
DIN DOUT
TOUCHSCREEN DATA
Figure 9b. Timing Diagram for Host-Initiated Keypad Debounce Scan
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 continues reading or writing until the rising edge of CS, or until it reaches the end of the page.
Table 2. Command Word Format
BIT15 MSB R/W BIT14 RES BIT13 RES BIT12 RES BIT11 RES BIT10 RES BIT9 RES BIT8 RES BIT7 RES BIT6 PAGE BIT5 ADD5 BIT4 ADD4 BIT3 ADD3 BIT2 ADD2 BIT1 ADD1 BIT0 LSB ADD0
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Table 3. Register Summary for MAX1233/MAX1234
PAGE ADDR (HEX) REGISTER NAME BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F
X 0 0 0 Y 0 0 0 Z1 0 0 0 Z2 0 0 0 KPD K15 K14 K13 BAT1 0 0 0 BAT2 0 0 0 AUX1 0 0 0 AUX2 0 0 0 TEMP1 0 0 0 TEMP2 0 0 0 DAC 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 GPIO GPD7 GPD6 GPD5 KPData1 K1_15 K1_14 K1_1 KPData2 K2_15 K2_14 K2_1 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved RES RES RES ADC PENSTS ADSTS A/D3 KEY KEYSTS1 KEYSTS0 DBN2 DAC DAPD 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 Reserved 0 0 0 GPIO PU7 PU6 PU5 Pullup GPIO GP7 GP6 GP5 KPKeyMask KM15 KM14 KM13 KPColumn CM4 CM3 CM2 Mask Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 K12 0 0 0 0 0 0 0 0 0 0 GPD4 K1_1 K2_1 0 0 0 0 0 0 0 0 0 0 0 0 0 RES A/D2 DBN1 0 0 0 0 0 0 0 0 0 0 0 0 PU4
X11 Y11 Z1_11 Z2_11 K11 B1_11 B2_11 A1_11 A2_11 T1_11 T2_11 0 0 0 0 GPD3 K1_11 K2_11 0 0 0 0 0 0 0 0 0 0 0 0 0 RES A/D1 DBN0 0 0 0 0 0 0 0 0 0 0 0 0 PU3
X10 Y10 Z1_10 Z2_10 K10 B1_10 B2_10 A1_10 A2_10 T1_10 T2_10 0 0 0 0 GPD2 K1_10 K2_10 0 0 0 0 0 0 0 0 0 0 0 0 0 RES A/D0 HLD2 0 0 0 0 0 0 0 0 0 0 0 0 PU2 GP2 KM10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X9 Y9 Z1_9 Z2_9 K9 B1_9 B2_9 A1_9 A2_9 T1_9 T2_9 0 0 0 0 GPD1 K1_9 K2_9 0 0 0 0 0 0 0 0 0 0 0 0 0 RES RES1 HLD1 0 0 0 0 0 0 0 0 0 0 0 0 PU1 GP1 KM9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X8 Y8 Z1_8 Z2_8 K8 B1_8 B2_8 A1_8 A2_8 T1_8 T2_8 0 0 0 0 GPD0 K1_8 K2_8 0 0 0 0 0 0 0 0 0 0 0 0 0 RES RES0 HLD0 0 0 0 0 0 0 0 0 0 0 0 0 PU0 GP0 KM8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X7 Y7 Z1_7 Z2_7 K7 B1_7 B2_7 A1_7 A2_7 T1_7 T2_7 DA7 0 0 0 0 K1_7 K2_7 0 0 0 0 0 0 0 0 0 0 0 0 0 RES AVG1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OE7 KM7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X6 Y6 Z1_6 Z2_6 K6 B1_6 B2_6 A1_6 A2_6 T1_6 T2_6 DA6 0 0 0 0 K1_6 K2_6 0 0 0 0 0 0 0 0 0 0 0 0 0 RES AVG2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OE6 KM6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X5 Y5 Z1_5 Z2_5 K5 B1_5 B2_5 A1_5 A2_5 T1_5 T2_5 DA5 0 0 0 0 K1_5 K2_5 0 0 0 0 0 0 0 0 0 0 0 0 0 RES CNR1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OE5 KM5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X4 Y4 Z1_4 Z2_4 K4 B1_4 B2_4 A1_4 A2_4 T1_4 T2_4 DA4 0 0 0 0 K1_4 K2_4 0 0 0 0 0 0 0 0 0 0 0 0 0 RES CNR0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OE4 KM4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X3 Y3 Z1_3 Z2_3 K3 B1_3 B2_3 A1_3 A2_3 T1_3 T2_3 DA3 0 0 0 0 K1_3 K2_3 0 0 0 0 0 0 0 0 0 0 0 0 0 RES ST2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OE3 KM3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X2 Y2 Z1_2 Z2_2 K2 B1_2 B2_2 A1_2 A2_2 T1_2 T2_2 DA2 0 0 0 0 K1_2 K2_2 0 0 0 0 0 0 0 0 0 0 0 0 0 RES ST1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OE2 KM2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X1 Y1 Z1_1 Z2_1 K1 B1_1 B2_1 A1_1 A2_1 T1_1 T2_1 DA1 0 0 0 0 K1_1 K2_1 0 0 0 0 0 0 0 0 0 0 0 0 0 RES ST0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OE1 KM1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
X0 Y0 Z1_0 Z2_0 K0 B1_0 B2_0 A1_0 A2_0 T1_0 T2_0 DA0 0 0 0 0 K1_0 K2_0 0 0 0 0 0 0 0 0 0 0 0 0 0 RES RFV 0 0 0 0 0 0 0 0 0 0 0 0 0 0 OE0 KM0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
GP4 GP3 KM12 KM11 CM1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
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 0x0040H. The succeeding 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--one 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, battery voltage, auxiliary analog inputs, and temperature. The ADC control register determines which input is selected and converted. Tables 4 and 5 show the format and bit descriptions for the ADC control register.
SCLK
CS
WRITE OPERATION
DIN
D15
D0
D15
D0
D15 IS READ/WRITE BIT LOW FOR WRITE
D15-D0 COMMAND WORD
D15-D0 DATA WORD
DOUT
THREESTATE
THREESTATE
TIMING NOT TO SCALE.
Figure 10a. Timing Diagram of Write Operation
SCLK
CS
READ OPERATION
DIN
D15 D14 D15-D0 COMMAND WORD
D0
DOUT THREE-STATE
D15 DATA WORD
D0
D15 DATA WORD
D0
THREE-STATE
Figure 10b. Timing Diagram of Read Operation
Table 4. ADC Control Register
BIT15 PENSTS BIT14 ADSTS BIT13 BIT12 BIT11 BIT10 A/D3 A/D2 A/D1 A/D0 BIT9 RES1 BIT8 RES0 BIT7 AVG1 BIT6 AVG0 BIT5 BIT4 BIT3 ST2 BIT2 ST1 BIT1 ST0 BIT0 RFV CNR1 CNR0
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
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 converter 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, regardless of read or write.
MAX1233/MAX1234
Table 5. ADC Control Register Bit Descriptions
BIT 15 (MSB) 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 (LSB) NAME PENSTS ADSTS A/D3 A/D2 A/D1 A/D0 RES1 RES0 AVG1 AVG0 CNR1 CNR0 ST2 ST1 ST0 RFV Read: ADC status; Write: stops ADC Selects ADC scan functions Selects ADC scan functions Selects ADC scan functions Selects ADC scan functions Controls ADC resolution Controls ADC resolution Controls ADC result averaging Controls ADC result averaging Controls ADC conversion rate Controls ADC conversion rate Controls touch-screen settling wait time Controls touch-screen settling wait time Controls touch-screen settling wait time Chooses 1.0V or 2.5V reference DESCRIPTION Read: pen interrupt status; Write: sets interrupt initiated touch-screen scans
Table 6. ADSTS Bit Operation
PENSTS 0 ADSTS 0 READ FUNCTION No screen touch detected; scan or conversion in progress Screen touch detected; scan or conversion in progress No screen touch detected; data available Screen touch detected; data available WRITE FUNCTION 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. Stops any ongoing scan and waits to detect a screen touch. Upon detection, issues an interrupt and performs a scan. 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. Stops any ongoing scan and powers down the screen touch detection circuit. No screen touches are detected in this mode.
1
0
0
1
1
1
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Table 7. ADC Scan Select (Touch Screen, Battery, Auxiliary Channels, and Temperature)
A/D3 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 A/D2 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 A/D1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 A/D0 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 FUNCTION Configures the ADC reference as selected by RES [1:0] bits as shown in Table 13. No measurement is performed. Measures X/Y touch position and returns results to the X and Y data registers. Measures X/Y touch position and Z1/ Z2 touch pressure and returns results to the X, Y, Z1, and Z2 data registers. Measures X touch position and returns results to the X data register. Measures Y touch position and returns results to the Y data register. Measures Z1/Z2 touch pressure and returns results to the Z1 and Z2 data register. Measures Battery Input 1 and returns results to the BAT1 data register. Measures Battery Input 2 and returns results to the BAT2 data register. Measures Auxiliary Input 1 and returns results to the AUX1 data register. Measures Auxiliary Input 2 and returns results to the AUX2 data register. Measures temperature (single ended) and returns results to the TEMP1 data register. Measures Battery Input 1, Battery Input 2, Auxiliary Input 1, Auxiliary Input 2, and temperature (differential), and returns results to the appropriate data registers. Measures temperature (differential) and returns results to the TEMP1 and TEMP2 data registers. Turns on Y+, Y- drivers. No measurement is performed. Turns on X+, X- drivers. No measurement is performed. Turns on Y+, X- drivers. No measurement is performed.
Table 8. ADC Resolution Control
RES1 0 0 1 1 RES0 0 1 0 1 ADC RESOLUTION 8 bit 8 bit 10 bit 12 bit INTERNALLY TIMED REFERENCE POWER-UP DELAY* (s) 31 31 37 44
Table 10. ADC Conversion Rate Control
CNR1 0 0 1 1 CNR0 0 1 0 1 FUNCTION 3.5s/sample (1.5s acquisition, 2s conversion) 3.5s/sample (1.5s acquisition, 2s conversion) 10s/sample (5s acquisition, 5s conversion) 100s/sample (95s acquisition, 5s conversion)
*Applicable only for temperature, battery, or auxiliary measurements in auto power-up reference mode.
Table 9. ADC Averaging Control
AVG1 0 0 1 1 AVG0 0 1 0 1 FUNCTION No data averages (default) 4 data averages 8 data averages 16 data averages
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
Bits 1-3: Touch-Screen Settling Time Control These bits specify the time delay from pen-touch detection 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-A/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 powerdown 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 contents, 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 keypad 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),
MAX1233/MAX1234
Table 11. Touch-Screen Settling Time Control*
ST2 0 0 0 0 1 1 1 1 ST1 0 0 1 1 0 0 1 1 ST0 0 1 0 1 0 1 0 1 SETTLING TIME Settling time: 0s Settling time: 100s Settling time: 500s Settling time: 1ms Settling time: 5ms Settling time: 10ms Settling time: 50ms Settling time: 100ms
Table 15. DAC Control Register Descriptions
BIT 15 (MSB) [14:0] NAME DAPD 0 DESCRIPTION DAC powered down Reserved
*Applicable only for X, Y, Z1, and Z2 measurements.
Table 12. ADC Reference Control Bit
RFV 0 1 FUNCTION +1.0V reference +2.5V reference
Table 16. DAC Power-Down Bit
DAPC 0 1 FUNCTION DAC powered up DAC powered down
Table 13. Internal ADC Reference Auto Power-Up Control
RES1 0 0 1 1 RES0 0 1 0 1 ADC REFERENCE SOURCE Internal Internal External External ADC REFERENCE POWER MODE Power up, wait for reference to settle, and power down again for each temperature, battery, or auxiliary scan (auto power-up mode) Always powered up Always powered down Always powered down
Table 14. DAC Control Register
BIT15 DAPD BIT14 0 BIT13 0 BIT12 0 BIT11 0 BIT10 0 BIT9 0 BIT8 0 BIT7 0 BIT6 0 BIT5 0 BIT4 0 BIT3 0 BIT2 0 BIT1 0 BIT0 0
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Table 17. Keypad Control Register
BIT15 KEYSTS1 BIT14 BIT13 BIT12 DBN1 BIT11 DBN0 BIT10 HLD2 BIT9 HLD BIT8 HLD BIT7 0 BIT6 0 BIT5 0 BIT4 0 BIT3 0 BIT2 0 BIT1 0 BIT0 0 KEYSTS0 DBN2
Table 18. Keypad Control Register Description
BIT 15 (MSB) 14 13 12 11 10 9 8 [7:0] NAME KEYSTS1 KEYSTS0 DBN2 DBN1 DBN0 HLD2 HLD1 HLD0 0 DESCRIPTION Read: keypad interrupt status; Write: set interrupt initiated keypad scans Read: keypad scan status; Write: stop keypad scan Keypad debounce time control Keypad debounce time control Keypad debounce time control Keypad hold time control Keypad hold time control Keypad hold time control Reserved
Table 19. KEYSTS1/KEYSTS0 Functions
KEYSTS1 0 KEYSTS0 0 READ FUNCTION No button press detected; scan or debounce in progress Button press detected; scan or debounce in progress No button press detected; data available Button press detected; data available WRITE FUNCTION Scans keypad once and waits to detect a button press. Upon detection, issues an interrupt and waits for the host's instruction before scanning. Stops any ongoing scan and waits to detect a button press. Upon detection, issues an interrupt and scans the keypad. Stops any ongoing scan and waits to detect a button press. Upon detection, issues an interrupt and waits for the host's instruction before scanning. Stops any ongoing scan and powers down the button press detection circuit. No button presses are detected in this mode.
1
0
0
1
1
1
Table 20. Keypad Debounce Time Control
DBN2 0 0 0 0 1 1 1 1 DBN1 0 0 1 1 0 0 1 1 DBN0 0 1 0 1 0 1 0 1 FUNCTION (ms) Debounce time: 2 Debounce time: 10 Debounce time: 20 Debounce time: 50 Debounce time: 60 Debounce time: 80 Debounce time: 100 Debounce time: 120
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
allowing certain keys to be masked from detection. Tables 18-21 show the programmable bits of the keypad control register. Tables 23, 24, and 25 show the programmable 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's 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 register descriptions. Tables 28 and 29 show the GPIO pullup disable register and associated descriptions. For more information, see the Applications Information section.
MAX1233/MAX1234
Table 21. Keypad Hold Time Control
HLD2 0 0 0 0 1 1 1 1 HLD1 0 0 1 1 0 0 1 1 HLD0 0 1 0 1 0 1 0 1 FUNCTION If a button is held, wait 100s before beginning next debounce scan If a button is held, wait 1 debounce time before beginning the next debounce scan If a button is held, wait 2 debounce times before beginning the next debounce scan If a button is held, wait 3 debounce times before beginning the next debounce scan If a button is held, wait 4 debounce times before beginning the next debounce scan If a button is held, wait 5 debounce times before beginning the next debounce scan If a button is held, wait 6 debounce times before beginning the next debounce scan If a button is held, wait 7 debounce times before beginning the next debounce scan
Table 22. Keypad Key Mask Control Register
BIT15 KM15 BIT14 KM14 BIT13 KM13 BIT12 KM12 BIT11 KM11 BIT10 KM10 BIT9 KM9 BIT8 KM8 BIT7 KM7 BIT6 KM6 BIT5 KM5 BIT4 KM4 BIT3 KM3 BIT2 KM2 BIT1 KM1 BIT0 KM0
Table 23. Keypad Key Mask Control Register Descriptions--Individual Mask
BIT 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 NAME KM15 KM14 KM13 KM12 KM11 KM10 KM9 KM8 KM7 KM6 KM5 KM4 KM3 KM2 KM1 KM0 DESCRIPTION Mask status register data update on individual key for row 4, column 4 Mask status register data update on individual key for row 3, column 4 Mask status register data update on individual key for row 2, column 4 Mask status register data update on individual key for row 1, column 4 Mask status register data update on individual key for row 4, column 3 Mask status register data update on individual key for row 3, column 3 Mask status register data update on individual key for row 2, column 3 Mask status register data update on individual key for row 1, column 3 Mask status register data update on individual key for row 4, column 2 Mask status register data update on individual key for row 3, column 2 Mask status register data update on individual key for row 2, column 2 Mask status register data update on individual key for row 1, column 2 Mask status register data update on individual key for row 4, column 1 Mask status register data update on individual key for row 3, column 1 Mask status register data update on individual key for row 2, column 1 Mask status register data update on individual key for row 1, column 1
Table 24. Keypad Column Mask Control Register
BIT15 CM4 BIT14 CM3 BIT13 CM2 BIT12 CM1 BIT11 0 BIT10 0 BIT9 0 BIT8 0 BIT7 0 BIT6 0 BIT5 0 BIT4 0 BIT3 0 BIT2 0 BIT1 0 BIT0 0
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Table 25. Keypad Column Mask Control Register Descriptions
BIT 15 14 13 12 [11:0] NAME CM4 CM3 CM2 CM1 0 DESCRIPTION Mask interrupt, status register, and pending register data update on all keys in column 4 Mask interrupt, status register, and pending register data update on all keys in column 3 Mask interrupt, status register, and pending register data update on all keys in column 2 Mask interrupt, status register, and pending register data update on all keys in column 1 Reserved
Table 26. GPIO Control Register
BIT15 GP7 BIT14 GP6 BIT13 GP5 BIT12 GP4 BIT11 GP3 BIT10 GP2 BIT9 GP1 BIT8 GP0 BIT7 OE7 BIT6 OE6 BIT5 OE5 BIT4 OE4 BIT3 OE3 BIT2 OE2 BIT1 OE1 BIT0 OE0
Table 27. GPIO Control Register Descriptions
BIT 15 14 13 12 11 10 9 8 [7:0] NAME GP7 GP6 GP5 GP4 GP3 GP2 GP1 GP0 [OE7:OE0] DESCRIPTION 1 C4 pin becomes GPIO pin 7 C3 pin becomes GPIO pin 6 C2 pin becomes GPIO pin 5 C1 pin becomes GPIO pin 4 R4 pin becomes GPIO pin 3 R3 pin becomes GPIO pin 2 R2 pin becomes GPIO pin 1 R1 pin becomes GPIO pin 0 GPIO pin configured as an output 0 C4 pin remains keypad column 4 C3 pin remains keypad column 3 C2 pin remains keypad column 2 C1 pin remains keypad column 1 R4 pin remains keypad row 4 R3 pin remains keypad row 3 R2 pin remains keypad row 2 R1 pin remains keypad row 1 GPIO pin configured as an input
Table 28. GPIO Pullup Disable Register
BIT15 PU7 BIT14 PU6 BIT13 PU5 BIT12 PU4 BIT11 PU3 BIT10 PU2 BIT9 PU1 BIT8 PU0 BIT7 0 BIT6 0 BIT5 0 BIT4 0 BIT3 0 BIT2 0 BIT1 0 BIT0 0
Table 29. GPIO Pullup Disable Register Descriptions
BIT [15:8] [7:0] NAME [PU7:PU0] 0 DESCRIPTION 1: Pullup disabled. Open collector output. 2: Pullup enabled. Reserved
Analog Input Data Registers Table 30 shows the format of the X, Y, Z1, Z2, 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 registers, while Tables 32, 33, and 34 provide individual register bit descriptions. These registers have the same format as the keypad mask register. Each bit represents one key on the keypad. Table 35 shows a map of a 16-key keypad. Data written through the serial interface to these registers is not stored.
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 0000H. The DAC register defaults to 1000H.
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Table 30. Analog Inputs Data Register Format
REGISTER BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 NAME X Y Z1 Z2 BATT1 BATT2 AUX1 AUX2 TEMP1 TEMP2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 X11 Y11 X10 Y10 X9 Y9 BIT8 X8 Y8 Z1_8 Z2_8 B1_8 B2_8 A1_8 A2_8 T1_8 T2_8 BIT7 X7 Y7 Z1_7 Z2_7 B1_7 B2_7 A1_7 A2_7 T1_7 T2_7 BIT6 X6 Y6 Z1_6 Z2_6 B1_6 B2_6 A1_6 A2_6 T1_6 T2_6 BIT5 X5 Y5 Z1_5 Z2_5 B1_5 B2_5 A1_5 A2_5 T1_5 T2_5 BIT4 X4 Y4 Z1_4 Z2_4 B1_4 B2_4 A1_4 A2_4 T1_4 T2_4 BIT3 X3 Y3 Z1_3 Z2_3 B1_3 B2_3 A1_3 A2_3 T1_3 T2_3 BIT2 X2 Y2 Z1_2 Z2_2 B1_2 B2_2 A1_2 A2_2 T1_2 T2_2 BIT1 X1 Y1 Z1_1 Z2_1 B1_1 B2_1 A1_1 A2_1 T1_1 T2_1 BIT0 X0 Y0 Z1_0 Z2_0 B1_0 B2_0 A1_0 A2_0 T1_0 T2_0
Z1_11 Z1_10 Z1_9 Z2_11 Z2_10 Z2_9 B1_11 B1_10 B1_9 B2_11 B2_10 B2_9 A1_11 A1_10 A1_9 A2_11 A2_10 A2_9 T1_11 T1_10 T1_9 T2_11 T2_10 T2_9
Table 31. Keypad Data Registers
REGISTER BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 NAME KBD KPData1 KPData2 K15 K14 K13 K12 K11 K10 K9 K1_15 K1_14 K1_13 K1_12 K1_11 K1_10 K1_9 K2_15 K2_14 K2_13 K2_12 K2_11 K2_10 K2_9 BIT8 K8 K1_8 K2_8 BIT7 K7 K1_7 K2_7 BIT6 K6 K1_6 K2_6 BIT5 K5 K1_5 K2_5 BIT4 K4 K1_4 K2_4 BIT3 K3 K1_3 K2_3 BIT2 K2 K1_2 K2_2 BIT1 K1 K1_1 K2_1 BIT0 K0 K1_0 K2_0
Table 32. Keypad Data Register Descriptions
BIT 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 NAME K15 K14 K13 K12 K11 K10 K9 K8 K7 K6 K5 K4 K3 K2 K1 K0 DESCRIPTION Keypad scan result for row 4, column 4. Can only be masked by column mask. Keypad scan result for row 3, column 4. Can only be masked by column mask. Keypad scan result for row 2, column 4. Can only be masked by column mask. Keypad scan result for row 1, column 4. Can only be masked by column mask. Keypad scan result for row 4, column 3. Can only be masked by column mask. Keypad scan result for row 3, column 3. Can only be masked by column mask. Keypad scan result for row 2, column 3. Can only be masked by column mask. Keypad scan result for row 1, column 3. Can only be masked by column mask. Keypad scan result for row 4, column 2. Can only be masked by column mask. Keypad scan result for row 3, column 2. Can only be masked by column mask. Keypad scan result for row 2, column 2. Can only be masked by column mask. Keypad scan result for row 1, column 2. Can only be masked by column mask. Keypad scan result for row 4, column 1. Can only be masked by column mask. Keypad scan result for row 3, column 1. Can only be masked by column mask. Keypad scan result for row 2, column 1. Can only be masked by column mask. Keypad scan result for row 1, column 1. Can only be masked by column mask.
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Table 33. Keypad Data Register 1 (Status Register) Descriptions
BIT 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 NAME 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 DESCRIPTION Keypad scan result for row 4, column 4. Can be masked by key mask or column mask. Keypad scan result for row 3, column 4. Can be masked by key mask or column mask. Keypad scan result for row 2, column 4. Can be masked by key mask or column mask. Keypad scan result for row 1, column 4. Can be masked by key mask or column mask. Keypad scan result for row 4, column 3. Can be masked by key mask or column mask. Keypad scan result for row 3, column 3. Can be masked by key mask or column mask. Keypad scan result for row 2, column 3. Can be masked by key mask or column mask. Keypad scan result for row 1, column 3. Can be masked by key mask or column mask. Keypad scan result for row 4, column 2. Can be masked by key mask or column mask. Keypad scan result for row 3, column 2. Can be masked by key mask or column mask. Keypad scan result for row 2, column 2. Can be masked by key mask or column mask. Keypad scan result for row 1, column 2. Can be masked by key mask or column mask. Keypad scan result for row 4, column 1. Can be masked by key mask or column mask. Keypad scan result for row 3, column 1. Can be masked by key mask or column mask. Keypad scan result for row 2, column 1. Can be masked by key mask or column mask. Keypad scan result for row 1, column 1. Can be masked by key mask or column mask.
Table 34. Keypad Data Register 2 (Pending Register) Descriptions
BIT 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 NAME 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 DESCRIPTION Keypad scan result for row 4, column 4. Can only be masked by column mask. Keypad scan result for row 3, column 4. Can only be masked by column mask. Keypad scan result for row 2, column 4. Can only be masked by column mask. Keypad scan result for row 1, column 4. Can only be masked by column mask. Keypad scan result for row 4, column 3. Can only be masked by column mask. Keypad scan result for row 3, column 3. Can only be masked by column mask. Keypad scan result for row 2, column 3. Can only be masked by column mask. Keypad scan result for row 1, column 3. Can only be masked by column mask. Keypad scan result for row 4, column 2. Can only be masked by column mask. Keypad scan result for row 3, column 2. Can only be masked by column mask. Keypad scan result for row 2, column 2. Can only be masked by column mask. Keypad scan result for row 1, column 2. Can only be masked by column mask. Keypad scan result for row 4, column 1. Can only be masked by column mask. Keypad scan result for row 3, column 1. Can only be masked by column mask. Keypad scan result for row 2, column 1. Can only be masked by column mask. Keypad scan result for row 1, column 1. Can only be masked by column mask.
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
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-bit 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-bit 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.
Applications Information
Programmable 8-/10-/12-Bit Resolution
The MAX1233/MAX1234 provide the option of three different 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 resolution is set to 8 bits with a 31s internally timed reference power-up delay as indicated by the ADC resolution control table. As explained in the control register section, the RES1 and RES0 bits control the reference
MAX1233/MAX1234
ADC Transfer Function
The MAX1233/MAX1234 output data is in straight binary 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.
OUTPUT CODE 11 ... 111 11 ... 110 11 ... 101
FULL-SCALE TRANSITION
MAX1233 MAX1234
Table 35. Keypad to Key Bit Mapping
COMPONENT R1 R2 R3 R4 C1 K0 K1 K2 K3 C2 K4 K5 K6 K7 C3 K8 K9 K10 K11 C4 K12 K13 K14 K15
00 ... 011 00 ... 010 00 ... 001 00 ... 000 0 1 23 INPUT VOLTAGE (LSB)
FS = VREF ZS = GND 1LSB = VREF 4096
FS FS - 3/2LSB
Figure 11. Ideal Input Voltages and Output Codes
Table 36. DAC Data Register
BIT15 0 BIT14 0 BIT13 0 BIT12 0 BIT11 0 BIT10 0 BIT9 0 BIT8 0 BIT7 DA7 BIT6 DA6 BIT5 DA5 BIT4 DA4 BIT3 DA3 BIT2 DA2 BIT1 DA1 BIT0 DA0
Table 37. GPIO Data Register
BIT15 GPD7 BIT14 GPD6 BIT13 GPD5 BIT12 GPD4 BIT11 GPD3 BIT10 GPD2 BIT9 GPD1 BIT8 GPD0 BIT7 0 BIT6 0 BIT5 0 BIT4 0 BIT3 0 BIT2 0 BIT1 0 BIT0 0
Table 38. GPIO Data Register Descriptions
BIT 15...8 7...0 NAME GPD7...0 0 GPIO data bits for GPIO pins 7...0 Reserved DESCRIPTION
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
+AVDD
FORCE LINE Y+
SENSE LINE X+
+IN
+REF CONVERTER -IN -REF
SENSE LINE
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 during 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.
FORCE LINE
Y-
Touch-Pressure Measurement
The MAX1233/MAX1234 provide two methods of measurement of the pressure applied to the touch screen. Although 8-bit resolution is typically sufficient, the following 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 position, use the following equation to calculate RTOUCH : X Z RTOUCH = RXPLATE x POSITION x 2 - 1 4096 Z1
GND
Figure 12. Ratiometric Y-Coordinate Measurement
power-up status when the A/D0-A/D3 bits are zero. These values can be set initially on power-up. (Subsequently A/D0-A/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 conversions. Figure 12 shows the switching matrix configuration for Y coordinate measurement. The +REF and -REF inputs are connected directly to Y+ and Y-. The conversion 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.
(
)
The second method requires knowing both the X-plate and Y-plate resistance. Three touch-screen conversions are required in this method as well for measurement of the X-position, Y-position, and Z- position of the touch screen. Use the following equation to calculate RTOUCH: X 4096 R RTOUCH = XPLATE x POSITION x - 1 Z1 4096 Z1 Y - RYPLATE x POSITION 4096
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-
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
FORCE LINE X+ Y+ SENSE LINE MEASURE X-POSITION
HOST WRITES ADC CONTROL REGISTER
BATTERY INPUT 1 OR BATTERY INPUT 2
TOUCH V X-POSITION
START CLOCK
XFORCE LINE
YOPEN CIRCUIT
SET BUSY LOW
MEASURE Z1-RESISTANCE
SENSE LINE X+ Y+
FORCE LINE
NO
IS ADC REFERENCE IN AUTO POWER-DOWN MODE? YES POWER UP REFERENCE
TOUCH V Z1-RESISTANCE
XFORCE LINE
YOPEN CIRCUIT
OPEN CIRCUIT X+
FORCE LINE Y+
POWER UP ADC
POWER DOWN ADC
TOUCH V Z2-RESISTANCE
CONVERT BATTERY INPUT 1 OR 2
POWER DOWN REFERENCE
SET BUSY HIGH
FORCE LINE XYSENSE LINE MEASURE Z2-RESISTANCE
NO
IS DATA AVERAGING DONE? TURN OFF CLOCK
Figure 13. Pressure Measurement Block Diagram
YES
DC/DC CONVERTER BATTERY 0.5V TO 6.0V VBAT 7.5k 2.7V
DONE STORE BATTERY INPUT 1 OR 2 IN BAT1 OR BAT2 REGISTER
AVDD
Figure 15. Battery Voltage-Reading Flowchart
Battery-Voltage Monitors
0.125V TO 1.5V CONVERTER
2.5k
Figure 14. Battery Measurement Block Diagram
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 voltage monitoring circuitry. The MAX1233/ MAX1234 directly 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.
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Auxiliary Analog Inputs
Two auxiliary analog inputs (AUX1 and AUX2) allow the MAX1233/MAX1234 to monitor analog input voltages from zero to VREF. Figure 16 illustrates the process of auxiliary input reading.
HOST WRITES ADC CONTROL REGISTER AUXILIARY INPUT 1 OR AUXILIARY INPUT 2
Temperature Measurements
The MAX1233/MAX1234 provide two temperature measurement options: a single-ended conversion method and a differential conversion method. Both temperature measurement techniques rely on the semiconductor junction's operational characteristics at a fixed current level. The forward diode voltage (VBE) vs. temperature is a well-defined characteristic. The ambient temperature can be predicted in applications by knowing the value of the VBE voltage at a fixed temperature and then monitoring 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/C. The single conversion method results in a resolution of 0.29C/LSB (2.5V reference) and 0.12C/LSB (1.0V reference) with a typical accuracy of 2C. Figure 18 shows the flowchart for the single temperature measurement. The differential conversion method uses two measurement 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: VBE = (kT/q) ln(N) where: VBE = difference in diode voltage N = current ratio of the second measurement to the first measurement k = Boltzmann's constant (1.38 x 10-23 eV/Kelvin) q = electron charge (1.60 x 10-19 C) T = temperature in Kelvin The resultant equation solving for K is: T(K) = q x V / (k x ln(N))
START CLOCK
SET BUSY LOW
NO
IS ADC REFERENCE IN AUTO POWER-DOWN MODE? YES POWER UP REFERENCE
POWER UP ADC
POWER DOWN ADC
CONVERT AUXILIARY INPUT 1 OR 2
POWER DOWN REFERENCE
SET BUSY HIGH NO IS DATA AVERAGING DONE? TURN OFF CLOCK
YES DONE STORE AUXILIARY INPUT 1 OR 2 IN AUX1 OR AUX2 REGISTER
Figure 16. Auxiliary Input Flowchart
MUX
A/D CONVERTER
TEMP1
TEMP2
Figure 17. Internal Block Diagram of Temperature Sensor 32 ______________________________________________________________________________________
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
HOST WRITES ADC CONTROL REGISTER TEMPERATURE INPUT 1 HOST WRITES ADC CONTROL REGISTER TEMPERATURE INPUT 1 AND TEMPERATURE INPUT 2
START CLOCK
START CLOCK
SET BUSY LOW
SET BUSY LOW
CONVERT TEMPERATURE INPUT 2
NO
IS ADC REFERENCE IN AUTO POWER-DOWN MODE? YES POWER UP REFERENCE
NO
IS ADC REFERENCE IN AUTO POWER-DOWN MODE? YES POWER UP REFERENCE
NO
IS DATA AVERAGING DONE?
YES STORE TEMPERATURE INPUT 2 IN TEMP2 REGISTER
POWER UP ADC
POWER DOWN ADC
POWER UP ADC
POWER DOWN ADC
CONVERT TEMPERATURE INPUT 1
POWER DOWN REFERENCE
CONVERT TEMPERATURE INPUT 1
POWER DOWN REFERENCE
SET BUSY HIGH NO IS DATA AVERAGING DONE? TURN OFF CLOCK NO IS DATA AVERAGING DONE?
SET BUSY HIGH
TURN OFF CLOCK
YES DONE STORE TEMPERATURE INPUT 1 IN TEMP1 REGISTER
YES DONE STORE TEMPERATURE INPUT 1 IN TEMP1 REGISTER
Figure 18. Single Temperature Measurement Process
Figure 19. Differential Temperature Measurement Process
where: V = V (I N) - V (I1) (in mV) T(K) = 2.68(K/mV) x V(mV) T(C) = [2.68(K/mV) x V(mV) - 273K]C/ 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 1.6C/LSB (2.5V reference) and 0.65C/LSB (1V reference) with a typical accuracy of 3C. Figure 19 shows the differential temperature measurementprocess. Note: The bias current for each diode temperature measurement is only turned ON during the acquisition and, therefore, does not noticeably increase power consumption.
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33
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Battery Voltage, Auxiliary Input, and Temperature Input Scan
Use this scan to make periodic measurements of both battery inputs, both auxiliary inputs, and both temperature inputs. The respective data registers have the latest results at the end of each cycle. Thus, a single write by the host to the MAX1233/MAX1234 ADC control register results in six different measurements being made. Figure 20 shows this scan operation. 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 control 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.
Touch-Initiated Screen Scans (PENSTS = 1; ADSTS = 0)
In the touch-initiated screen-scan mode, the MAX1233/MAX1234 automatically perform a touchscreen scan upon detecting a screen touch. The touchscreen 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 Xand Y- coordinate scan. Selection of resolution, conversion rate, averaging, and touch-screen settling time determine the overall conversion time. Figure 22 shows the complete flowchart for a touchinitiated 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 touchscreen scan begins. The MAX1233/MAX1234 detect a screen touch and drive PENIRQ LOW. The host recognizes 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.
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's VOUT to be adjustable. The minimum and maximum DAC voltages (VDAC(HIGH) and V DAC(LOW) ) can be found in the Electrical Characteristics table. The output voltage of the MAX1677 (VOUT) can be calculated by noting the following equations: VOUT = VREFDAC + i1R1 [Equation 1] i1 = i2 + i3 [Equation 2] [Equation 3] i2 = VREFDAC / R2 i3 = (VREFDAC - VDAC) / R3 [Equation 4] Substituting equations 2, 3, and 4 into equation 1 yields: VOUT = VREFDAC + (R1 / R2) VREF + (R1 / R3) (VREFDAC - VDAC) [Equation 5]
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
BATTERY VOLTAGE, AUXILIARY INPUT, AND TEMPERATURE INPUT SCAN ([A/D3:A/D0] = 1011)
HOST WRITES ADC CONTROL REGISTER
CONVERT BATTERY INPUT 2
CONVERT TEMPERATURE INPUT 1
START CLOCK
SET BUSY LOW
NO
IS DATA AVERAGING DONE?
NO
IS DATA AVERAGING DONE?
NO
IS ADC REFERENCE IN AUTO POWER-DOWN MODE? YES POWER UP REFERENCE
YES STORE BATTERY INPUT 2 IN BAT2 REGISTER
YES STORE TEMPERATURE INPUT 1 IN TEMP1 REGISTER
CONVERT AUXILIARY INPUT 1
CONVERT TEMPERATURE INPUT 2
POWER UP ADC
NO
IS DATA AVERAGING DONE?
NO
IS DATA AVERAGING DONE?
CONVERT BATTERY INPUT 1
YES STORE AUXILIARY INPUT 1 IN AUX1 REGISTER
YES STORE TEMPERATURE INPUT 2 IN TEMP2 REGISTER
NO
IS DATA AVERAGING DONE?
CONVERT AUXILIARY INPUT 2
POWER DOWN ADC
YES POWER DOWN REFERENCE STORE BATTERY INPUT 1 IN BAT1 REGISTER NO IS DATA AVERAGING DONE?
SET BUSY HIGH
YES STORE AUXILIARY INPUT 2 IN AUX2 REGISTER
TURN OFF CLOCK
DONE
Figure 20. Scan Mode Flowchart ______________________________________________________________________________________ 35
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
PENIRQ-INITIATED X- AND Y- SCREEN SCAN SCREEN TOUCH
POWER DOWN ADC
YES
ARE THERE UNREAD SCAN RESULTS? NO SET PENIRQ LOW
TURN ON DRIVERS: X+. X-
NO
IS TOUCH-SCREEN SETTLING DONE?
YES GO TO NO HOST-INITIATED SCAN (FIGURE 23) POWER UP ADC
IS PENSTS BIT = 1?
CONVERT Y- COORDINATES YES START CLOCK NO SET BUSY LOW YES TURN ON DRIVERS: Y+, YSTORE Y- COORDINATES IN Y- REGISTER IS DATA AVERAGING DONE?
NO
IS TOUCH-SCREEN SETTLING DONE?
POWER DOWN ADC
SET BUSY HIGH YES POWER UP ADC TURN OFF CLOCK
CONVERT X- COORDINATES
RESET PENIRQ HIGH
DONE NO IS DATA AVERAGING DONE?
YES STORE X- COORDINATES IN X- REGISTER
Figure 21. Touch-Initiated X- and Y- Coordinate Screen Scan 36 ______________________________________________________________________________________
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
PENIRQ-INITIATED X, Y, AND Z SCREEN SCAN
SCREEN TOUCH STORE X- COORDINATES IN X- REGISTER CONVERT Z1- COORDINATES
YES
ARE THERE UNREAD SCAN RESULTS?
POWER DOWN ADC NO TURN ON DRIVERS: X+, XYES STORE Z1- COORDINATES IN Z1- REGISTER IS DATA AVERAGING DONE?
NO SET PENIRQ LOW NO GO TO HOST-INITIATED SCAN (FIGURE 24)
IS TOUCH-SCREEN SETTLING DONE?
IS PENSTS BIT = 1?
CONVERT Z2 COORDINATES YES POWER UP ADC
YES START CLOCK CONVERT Y- COORDINATES NO IS DATA AVERAGING DONE?
SET BUSY LOW NO TURN ON DRIVERS: Y+, YIS DATA AVERAGING DONE?
YES STORE Z2- COORDINATES IN Z2- REGISTER
YES STORE Y- COORDINATES IN Y- REGISTER
POWER UP ADC
NO
IS TOUCH-SCREEN SETTLING DONE?
SET BUSY HIGH POWER DOWN ADC
YES TURN OFF CLOCK POWER UP ADC TURN ON DRIVERS: Y+, XRESET PENIRQ HIGH CONVERT X- COORDINATES NO IS TOUCH-SCREEN SETTLING DONE?
DONE
NO
IS DATA AVERAGING DONE?
YES POWER UP ADC
Figure 22. Touch-Initiated X- , Y-, and Z- Coordinate Screen Scan ______________________________________________________________________________________ 37
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
HOST-INITIATED X- AND Y- SCREEN SCAN SCREEN TOUCH
STORE X- COORDINATES IN X- REGISTER
POWER DOWN ADC YES ARE THERE UNREAD SCAN RESULTS? TURN ON DRIVERS: X+, XNO SET PENIRQ LOW NO IS TOUCH-SCREEN SETTLING DONE?
IS PENSTS BIT = 1?
YES
GO TO TOUCH-INITIATED SCAN (FIGURE 21)
YES POWER UP ADC
NO HOST WRITES ADC CONTROL REGISTER (PENSTS = ADSTS = 0)
CONVERT Y- COORDINATES
SET BUSY LOW
NO
IS DATA AVERAGING DONE?
START CLOCK
YES STORE Y- COORDINATES IN Y- REGISTER
TURN ON DRIVERS: Y+, YPOWER DOWN ADC
NO
IS TOUCH-SCREEN SETTLING DONE?
SET BUSY HIGH
YES POWER UP ADC
TURN OFF CLOCK
RESET PENIRQ HIGH CONVERT X- COORDINATES DONE
NO
IS DATA AVERAGING DONE?
YES
Figure 23. Host-Initiated X- and Y- Coordinate Screen Scan 38 ______________________________________________________________________________________
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
HOST-INITIATED X-, Y-, AND Z- SCREEN SCAN TURN ON DRIVERS: Y+, XSCREEN TOUCH
NO YES ARE THERE UNREAD SCAN RESULTS? NO SET PENIRQ LOW
IS TOUCH-SCREEN SETTLING DONE?
TURN ON DRIVERS: X+, X-
YES POWER UP ADC
NO
IS TOUCH-SCREEN SETTLING DONE?
CONVERT Z1- COORDINATES
IS PENSTS BIT = 1?
YES
GO TO TOUCH-INITIATED SCAN (FIGURE 22)
YES POWER UP ADC NO IS DATA AVERAGING DONE?
NO HOST WRITES ADC CONTROL REGISTER YES STORE Z1- COORDINATES IN Z1- REGISTER
CONVERT Y- COORDINATES
START CLOCK
NO
IS DATA AVERAGING DONE?
CONVERT Z2- COORDINATES
SET BUSY LOW YES STORE Y- COORDINATES IN Y- REGISTER NO IS DATA AVERAGING DONE?
TURN ON DRIVERS: Y+, Y-
POWER DOWN ADC NO IS TOUCH-SCREEN SETTLING DONE?
YES STORE Z2- COORDINATES IIN Z2- REGISTER
YES POWER UP ADC
POWER DOWN ADC
SET BUSY HIGH CONVERT X- COORDINATES
TURN OFF CLOCK NO IS DATA AVERAGING DONE?
YES STORE X- COORDINATES IN X- REGISTER
RESET PENIRQ HIGH
DONE POWER DOWN ADC
Figure 24. Host-Initiated X-, Y-, and Z- Coordinate Screen Scan ______________________________________________________________________________________ 39
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
HOST-INITIATED DEBOUNCE SCAN KEY-PRESS-INITIATED DEBOUNCE SCAN KEYPAD TOUCH KEYPAD TOUCH
YES YES ARE THERE UNREAD DEBOUNCE RESULTS?
ARE THERE UNREAD DEBOUNCE RESULTS?
NO SET KEYIRQ LOW
NO SET KEYIRQ LOW
IS KEYSTS1 = 1? NO GO TO HOST-INITIATED DEBOUNCE SCAN
YES
GO TO KEY-PRESS-INITIATED DEBOUNCE SCAN
IS KEYSTS1 = 1?
NO HOST WRITES ADC CONTROL REGISTER
YES START CLOCK
START CLOCK SET BUSY LOW
SET BUSY LOW SCAN AND DEBOUNCE KEYS
STORE KEYPAD SCAN RESULTS IN REGISTER
SCAN AND DEBOUNCE KEYS
STORE KEYPAD SCAN RESULTS IN REGISTER SET BUSY HIGH SET BUSY HIGH RESET KEYIRQ HIGH RESET KEYIRQ HIGH DONE DONE
Figure 25. Key-Press-Initiated Debounce Scan 40
Figure 26. Host-Initiated Debounce Scan
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
VBATT
MAX1233 MAX1234
AVDD
FEEDBACK RESISTORS DACOUT R3
SIMPLIFIED DC/DC CONVERTER ERROR AMP
R1
i1
DAC
i3
R2
i2
VREF 1.25V
CONTROL VOUT (LCD BIAS)
MAX1677
Figure 27. LCD Contrast Control Circuit
CS SCK MISO SPI VDD MOSI DIN BUSY PENIRQ KEYIRQ SS CS DCLK DOUT CS SCK MISO CS DCLK DOUT
MAX1233 MAX1234
MICROWIRE MOSI DIN BUSY PENIRQ KEYIRQ
MAX1233 MAX1234
Figure 28a. SPI Interface
Figure 28b. MICROWIRE Interface
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 VOUTMAX using the following equation: VOUTMAX = VREFMAX + (R1MAX / R2MIN)VREFMAX + (R1MAX / R3MIN) (VREFMAX - VDACMIN) [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 VOUTMIN using the following equation: VOUTMIN= VREFMIN + (R1MIN / R2MAX)VREFMIN + (R1MAX / R3MIN) (VREFMIN - VDACMAX) [Equation 7] If VOUTMIN 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's falling edge and is clocked into the P on the DCLK's rising edge. The first
41
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
CS SCK MISO QSPI VDD MOSI DIN BUSY PENIRQ KEYIRQ SS CS DCLK DOUT
MAX1233 MAX1234
Figure 29. QSPI Interface
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 operation, the ground return to the star ground's 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 0.1F capacitor as close to pins 1 and 2 of the MAX1233/MAX1234 as possible. Minimize capacitor lead lengths for best supply-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 converter 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 "flickering" 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 Xinputs to ground also help reduce the noise further. Caution should be observed for settling time of the touch screen.
SUPPLIES +3V/+5V GND +3V/+5V
R* = 10
AVDD
GND
DVDD
VDD
DGND
MAX1233 MAX1234
*OPTIONAL
DIGITAL CIRCUITRY
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.
Figure 30. Power-Supply Grounding Connection
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 support a maximum fSCLK of 10MHz. DOUT data transitions on the serial clock's falling edge and is clocked into the P on the DCLK's rising edge.
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.
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
42
Aperture Jitter
Aperture jitter (tAJ) is the sample-to-sample variation in the time between the samples.
Aperture Delay
Aperture delay (tAD) is the time defined between the falling edge of the sampling clock and the instant when an actual sample is taken.
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15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital samples, 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 analogto-digital noise is caused by quantization error only and results directly from the ADC's resolution (N bits): SNR = (6.02 N + 1.76) dB In reality, there are other noise sources besides quantization 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 harmonics, and the DC offset.
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: V 2 + V32 + V4 2 + V52 THD = 20 x log 2 V12
MAX1233/MAX1234
where V1 is the fundamental amplitude, and V2 through V5 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 component) to the RMS value of the next-largest distortion component.
Signal-to-Noise Plus Distortion
Signal-to-noise plus distortion (SINAD) is the ratio of the fundamental input frequency's RMS amplitude to the RMS equivalent of all other ADC output signals: SINAD (dB) = 20 log (SignalRMS / NoiseRMS)
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's 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
Chip Information
TRANSISTOR COUNT: 28,629
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43
15kV ESD-Protected Touch-Screen Controllers Include DAC and Keypad Controller MAX1233/MAX1234
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
32L QFN.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit 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 (c) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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