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austriamicrosystems ag is now ams ag the technical content of this austriamicrosystems datasheet is still valid. contact information: headquarters: ams ag tobelbaderstrasse 30 8141 unterpremstaetten, austria tel: +43 (0) 3136 500 0 e - mail: ams_sales @ams.com please visit our website at www.ams.com
a s3 8 3 3 6 c h a n n e l h i g h - p re c i s i o n l e d c o n tr o l l e r fo r 3 d- l c d b a ck l i g h t w i t h i n t eg ra t e d s te p - u p c o n t r o l l e r www.austriamicrosystems.com/as3833 revision 1.8 1 - 20 d atas he et 1 general description the as3833 is a 6 channel high precision led controller with pwm input for driving external bipolar transistors in lcd-backlight panels, optimized for 2d and 3d operation. the integrated step-up controller provides the necessary output voltage for the led string supply. the smps feedback control optimizes the power efficiency by adjusting the led string supply voltage. build in safety features include under-voltage and thermal shutdown as well as open and short led detection. 2 key features 6 channel led controller step-up controller optimized for 2d/3d mode supply voltage range: 12v to 50v figure 1. as3833 output current up to 250ma per channel absolute current accuracy +/- 0.8% channel to channel accuracy+/- 0.6% 1 pwm input with internal phase shift open led detection and disconnect short led protection and auto-turnoff undervoltage shutdown temperature shutdown temperature supervision of external bjt bjt beta compensation smps feedback control dcdc softstart function over voltage protection (ovp) package soic-28 package tqfp-32 3 applications led backlighting for 3d-lcd backlight tv sets and monitors ams ag technical content still valid
revision 1.8 2 - 20 as3833 datasheet - c o n t e n t s contents 1 general description .................................................................................................................................................................. 1 2 key features ............................................................................................................................................................................ 1 3 applications .............................................................................................................................................................................. 1 4 pin assignments (top view) ..................................................................................................................................................... 3 4.1 pin descriptions .................................................................................................................................................................................. 4 5 absolute maximum ratings ...................................................................................................................................................... 5 6 electrical characteristics .......................................................................................................................................................... 6 7 typical operating characteristics ............................................................................................................................................. 8 8 detailed description ............................................................................................................................................................... 10 8.1 precision current output ..................................................................................................................................................................... 10 8.1.1 phase shift .............................................................................................................................................................................. 10 8.2 vddh_hc resistor ............................................................................................................................................................................. 11 8.3 safety features ................................................................................................................................................................................... 11 8.3.1 undervoltage lockout .............................................................................................................................................................. 11 8.3.2 overtemperature shutdown ................................................................................................................................................... 12 8.3.3 short led protection .............................................................................................................................................................. 12 8.3.4 open led detection ............................................................................................................................................................... 13 8.4 boost controller .................................................................................................................................................................................. 13 8.4.1 setting the output voltage ....................................................................................................................................................... 14 8.4.2 continuous conduction mode (ccm) .................................................................................................................................... 15 8.4.3 duty cycle .............................................................................................................................................................................. 15 8.4.4 inductor current ..................................................................................................................................................................... 15 8.4.5 input capacitor ....................................................................................................................................................................... 16 8.4.6 output capacitor .................................................................................................................................................................... 16 8.4.7 current sense resistor .......................................................................................................................................................... 16 8.4.8 compensation network .......................................................................................................................................................... 16 9 package drawings and markings ........................................................................................................................................... 17 10 ordering information ............................................................................................................................................................. 20 ams ag technical content still valid
revision 1.8 3 - 20 as3833 datasheet - p i n a s s i g n m e n t s ( to p v i e w ) 4 pin assignments (top view) figure 2. pin assignments (top view) ams ag technical content still valid
revision 1.8 4 - 20 as3833 datasheet - p i n a s s i g n m e n t s ( to p v i e w ) 4.1 pin descriptions a_i/o...analog pin, p...power pin, do...digital output, do_od...digital output open drain, di...digital input, di_pu...digital input with pullup resistor, di_pd...digital input with pull down resistor table 1. pin descriptions pin number as3833 tqfp-32 pin number as3833 soic-28 pin name pin type description 29 1 vss p analog ground 30 2 b4 a_i/o base 4. connect to base of external transistor. 31 3 e4 a_i/o emitter 4. connect to emitter of external transistor. 1 4 xfault do_od fault output. active low. 2 5 iset a_i/o current setting. connect current setting resistor. 3 6 uvlo a_i/o undervoltage lockout input. 4 7 comp a_i/o compensation network. connect compensation network. 5 8 sense a_i/o current sense input . provide a short, direct pcb path between this pin and the positive side of the current sense resistor. 6 9 fb a_i/o output voltage feedback input. input for voltage divider. connect voltage divider output as short as possible to this pin 7 10 vddl a_i/o voltage regulator output 3.3v. connect 2.2 f decoupling capacitor to gnd 8 11 gate a_i/o gate driver output. 10 12 pgnd p power ground 11 13 vddm p voltage regulator output. connect 2.2 f decoupling capacitor to gnd 12 14 vddh p supply voltage. connect 1 f decoupling capacitor to gnd 14 15 vddh_hc p voltage regulator input. connect 2.2 f decoupling capacitor to gnd 15 16 vth a_i/o reference input for overtemperature detection. 16 17 pwm1 di_pd pwm input 1. pwm input for channel 1 17 18 e6 a_i/o emitter 6. connect to emitter of external transistor. 18 19 b6 a_i/o base 6. connect to base of external transistor. 19 20 b5 a_i/o base 5. connect to base of external transistor. 20 21 e5 a_i/o emitter 5. connect to emitter of external transistor. 21 22 vss p analog ground 22 23 e2 a_i/o emitter 2. connect to emitter of external transistor. 23 24 b2 a_i/o base 2. connect to base of external transistor. 24 25 b1 a_i/o base 1. connect to base of external transistor. 25 26 e1 a_i/o emitter 1. connect to emitter of external transistor. 26 27 e3 a_i/o emitter 3. connect to emitter of external transistor. 27 28 b3 a_i/o base 3. connect to base of external transistor. ams ag technical content still valid
revision 1.8 5 - 20 as3833 datasheet - a b s o l u t e m a x i m u m r a t i n g s 5 absolute maximum ratings stresses beyond those listed in table 2 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 electrical characteristics on page 6 is not implied. exposure to absolute m aximum rating conditions for extended periods may affect device reliability. table 2. absolute maximum ratings parameter min max units comments electrical parameters vddh to vss, vddh_hc to vss -0.3 55 v vddm to vss, gate to vss -0.3 25 v xfault to vss -0.3 7 v vddl to vss -0.3 5 v analog pin voltage to vss 1 1. pins vth, uvlo, comp, sense, fb, iset, ex, bx -0.3 5 v digital pin voltage to vss 2 2. pins pwmx -0.3 5 v input current (latch-up immunity) -100 100 ma norm: jedec 78 electrostatic discharge electrostatic discharge hbm +/- 1500 v norm: mil 883 e method 3015 electrostatic discharge mm +/- 200 v norm: jesd22-a115c continuos power dissipation (t a = +70c) continuos power dissipation 1.5 w p t 3 for soic-28 package 3. depending on actual pcb layout and pcb used. continuos power dissipation derating factor 13 mw / c p derate 4 4. p derate derating factor changes the total continuous power dissipation (p t ) if the ambient temperature is not 25oc. therefore for e.g. t a =85oc calculate p t at 85oc = p t - p derate x (85oc - 25oc) temperature ranges and storage conditions junction to ambient thermal resistance 76 oc/w soic-28 package. for more information about thermal metrics, see application note an01 thermal characteristics . junction temperature (t jmax ) +150 oc storage temperature range -55 +150 oc package body temperature +260 oc the reflow peak soldering temperature (body temperature) specified is in accordance with ipc/ jedec j-std-020?moisture/reflow sensitivity classification for non-hermetic solid state surface mount devices?. the lead finish for pb-free leaded packages is matte tin (100% sn). humidity non-condensing 5 85 % moisture sensitive level 1 represents a max. floor life time of unlimited ams ag technical content still valid
revision 1.8 6 - 20 as3833 datasheet - e l e c t r i c a l c h a r a c t e r i s t i c s 6 electrical characteristics vddh = 24v, all voltages referenced to v ss , typical values are at t a = +25c (unless otherwise specified). all limits are guaranteed. the parameters with min. and max values are guaranteed with production tests or sqc (statistical quality control) methods. table 3. electrical characteristics symbol parameter conditions min typ max units general t a operating temperature range apply proper cooling to stay below maximum allowed tj. -20 +85 c t j operating junction temperature -20 +115 c power supply v ddh supply voltage +12 +50 v v ddm driver supply voltage regulator output +9 v v ddl 3v voltage regulator output +3.3 v i dd operating current consumption uvlo=2v, pwm1=0, rset=6k , vth=0.47v 4.6 5.0 5.6 ma i dd q quiescent current consumption uvlo=0v, pwm1=0, rset=6k , vth=0.47v 2.25 2.50 2.75 ma current sink parameters i led_100 trimmed current accuracy iled=100ma, tj = 25c excluding error of rset -0.8 +0.8 % i led_all current accuracy iled=50 1 to 250ma, bjt >50 tj = -20 to +115c -1.5 +1.5 % i ch_100 channel to channel accuracy iled=100ma, tj = 25c -0.6 +0.6 % v isetx reference voltage at pins iset +1.18 +1.20 +1.22 v ratio ratio = iled/iset 500 i bx base output current limit 5.5 7.5 ma short detection comparator acc short over-temperature protection accuracy accuracy of v be comparison with v th level -10 +10 mv power supply regulation b th bjt beta threshold 45 48 52 boost controller oscillator f osc oscillator frequency 220 250 280 khz boost controller pwm d max maximum duty cycle 85 87 89 % boost controller error amplifier v fb reference voltage at pin fb +1.23 +1.25 +1.27 v a v voltage gain 80 db bw bandwidth av = 0db 2 mhz i fb_in voltage sense input current pins fb 0.1 0.2 a i comp_out compensation output current pins comp, vcomp = 1v 10 a boost controller over current protection v sense current sense threshold pin sense +600 +800 +1000 mv ams ag technical content still valid
revision 1.8 7 - 20 as3833 datasheet - e l e c t r i c a l c h a r a c t e r i s t i c s boost controller driver r driver driver resistance sink and source pin gate 4 6 8 v driver gate maximum output voltage igate = 0ma vddm v t rise_driver gate voltage rise time vgate = 0 to 3v, cload = 3nf 15 25 50 ns t fall_driver gate voltage fall time vgate = 3 to 0v, cload = 3nf 15 25 50 ns boost controller under voltage lockout v uvlo under voltage lockout threshold +1.28 +1.35 +1.42 v i uvlo_hyst under voltage lockout hysteresis current 20 a digital pins v ih logic high input threshold +1.8 v v il logic low input threshold +0.8 v v ol logic low output level pin xfault open drain. i = -2ma +0.3 v r pu input resistance pull-up inputs 300 k r pd input resistance pull-down inputs 300 k thermal protection t off thermal shutdown threshold 140 c t hyst thermal shutdown hysteresis 30 c 1. is is not recommended to set iled < 50ma in order to minimize influences of offset voltages. table 3. electrical characteristics (continued) symbol parameter conditions min typ max units ams ag technical content still valid
revision 1.8 8 - 20 as3833 datasheet - ty p i c a l o p e r a t i n g c h a r a c t e r i s t i c s 7 typical operating characteristics v out boost = 60v; i out = 1a, t amb = +25oc (unless otherwise specified). figure 3. boost - efficiency vs. output current; v in = 13v figure 4. boost - efficiency vs. output current; v in = 24v figure 5. v out vs. i out ,v in = 13v 0 10 20 30 40 50 60 70 80 90 100 0,1 1 10 output current (a) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0,1 1 10 output current (a) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0 0,5 1 1,5 2 2,5 3 3,5 4 output current (a) output voltage (v) ams ag technical content still valid
revision 1.8 9 - 20 as3833 datasheet - ty p i c a l o p e r a t i n g c h a r a c t e r i s t i c s figure 6. v out vs. i out ,v in = 24v figure 7. boost - efficiency vs. input voltage, i out = 1a figure 8. v out vs. temp ,v in = 24v, i out = 0.2a 0 10 20 30 40 50 60 70 80 90 100 0 0,5 1 1,5 2 2,5 3 3,5 4 output current (a) output voltage (v) 0 10 20 30 40 50 60 70 80 90 100 10 12 14 16 18 20 22 24 26 28 30 input voltage (v) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 -30 -15 0 15 30 45 60 75 90 temperature (c) output voltage (v) ams ag technical content still valid
revision 1.8 10 - 20 as3833 datasheet - d e t a i l e d d e s c r i p t i o n 8 detailed description 8.1 precision current output figure 9. current output stage the led-current is derived from either rset using the following equation i set is protected against a short to ground. in the case of a ground short the current i set is limited to 660ua and the led-current to 330ma. i set has a lower limit of 6ua with a 1ua hysteresis.this sets the lower limit of the led-current to 3ma with r set =200k . if r set is large than 200k , the led-current is set to 0ma. 8.1.1 phase shift the outputs are controlled by the pwm-input and a built in phase shift generator. all outputs are phase shifted by 1/6 of the pwm-period. in order to calculate the phase shift timing, two pwm-periods are needed. this means that after changing the pwm-frequency, the phase shift is updated after the second period. the pwm-frequency must be in the range from 60hz to 1khz. figure 10. phase shift i led ratio i set = ratio v set r set --------- 500 1.2v r set ------------ = = (eq 1) ams ag technical content still valid
www.austriamicrosystems.com/as3833 revision 1.8 1 1 - 20 as3833 datasheet 8.2 vddh_hc resistor figure 11. vddh_hc resistor pin vddh_hc is connected to an internal 3.3v voltage regulator. in order to keep the power dissipation of this regulator low, it is recommended to connect pin vddh_hc to the power supply vin with a resistor. the resistor should guarantee sufficient voltage drop so that the remaining voltage at pin vddh_hc is approximately 5v. the power dissipation of the r vddh_hc hat to be considered. typical values for r vvdh2 are: vin = 13v: r vddh_hc = 100 / 1w vin = 24v: r vddh_hc = 250 / 2w 8.3 safety features 8.3.1 undervoltage lockout in order to avoid startup of the boost controller at low supply voltage an undervoltage lockout function is implemented. the boost controller only turns on when the voltage at pin uvlo exceeds v uvlo. once the boost controller is turned on a current source i uvlo_hyst is activated which increases the uvlo voltage and so shifts the turn off voltage level. figure 12. undervoltage lockout r vddh _ hc v in 5 v ? 75 ma -------------------- = (eq 2) p r vddh _hc 75 ma ( ) 2 r vddh _ hc = (eq 3) ams ag technical content still valid
revision 1.8 12 - 20 as3833 datasheet - d e t a i l e d d e s c r i p t i o n following equations can be derived for adjusting the threshold voltages: 8.3.2 overtemperature shutdown if the device temperature reaches t off the boost controller and all current outputs are turned off. after the temperature has decreased by t hyst all blocks are turned on again. 8.3.3 short led protection figure 13. short led protection a built in short protection comparator is monitoring the junction temperature t j of the external bipolar transistors by measuring the base-emitter voltage v be . when the measured v be gets lower than the voltage applied at pin vth an overtemperature an hence an short led condition is detected. subsequently the fault output is activated (xfault = 0) and the corresponding output is deactivated. v ddh_uvh v uvlo 1 r uvlo 1 r uvlo 2 ------------------- + ? ? ? ? = (eq 4) undervoltage lockout high level: v ddh_uvl v uvlo 1 r uvlo 1 r uvlo 2 ------------------- + ? ? ? ? i uvlo r uvlo 1 ? = (eq 5) undervoltage lockout low level: v be 1,2v 0.002 t j tj....junction temperature in k ?= (eq 6) ams ag technical content still valid
revision 1.8 13 - 20 as3833 datasheet - d e t a i l e d d e s c r i p t i o n 8.3.4 open led detection figure 14. open led detection a broken led-string is detected during pwm=1. if a led-string is broken the power supply feedback will increment the idac to increase the power supply output voltage. after the idac has reached its maximum value, a debounce counter is started. in order to run the debounce counter, the corresponding pwm-signal has to be high for more than 150us. after the debounce counter has counted up for 32ms, the fault output is activated (xfault = 0) and the corresponding output is disconnected from the power supply feedback loop. 8.4 boost controller figure 15. boost controller ams ag technical content still valid
revision 1.8 14 - 20 as3833 datasheet - d e t a i l e d d e s c r i p t i o n 8.4.1 setting the output voltage figure 16. vout setting according to the requirements of the led strings, the output voltage vout is adjusted by the internal power supply feedback between: and once vout_min and vout_max is known the external resistors can be caluclated: note: the overall resistance should be in the range of 100k to 200k to avoid any noise issues. keep fb-line as short as possible. v outmin v fb 1 r fb 1 r fb 2 ---------- + ? ? ? ? v outmax v fb 1 r fb 1 r fb 2 ---------- + ? ? ? ? a r fb 1 ? + = r fb 1 v outmax v outmin ? ( ) 255 a ------------------------------------------------------- = (eq 7) r fb 2 v fb r fb 1 v outmin v fb ? ( ) ---------------------------------------- = (eq 8) ams ag technical content still valid
revision 1.8 15 - 20 as3833 datasheet - d e t a i l e d d e s c r i p t i o n 8.4.2 continuous conduction mode (ccm) for normal operation the converter should stay in continuous conduction mode, to ensure that the inductor value must be bigger than l crit . where: v in ... input voltage at vddh v out ... output voltage v d ... diode forward voltage at d1 f sw ... switching frequency r ... load resistor, should be calculated with minimum current load r = v out / i out_min i out_min ... minimum output current (e.g. for led driver only one led string is on) 8.4.3 duty cycle within ccm, the well known relation between input and output voltage is deriped in the following equation: this means for the duty cycle: 8.4.4 inductor current the inductor current varies during a switching cycle. this variation can be expressed by the mean value of the inductor current and the delta rise/ fall current within each cycle (see figure 17) . f igure 17. inductor current mean inductor current: delta inductor current: (eq 9) l crit 1 v in v out v d + --------------------------- ? ? ? ? ? v 2 in r 2 f sw v out v d + ( ) 2 ---------------------------------------------------------------------- = (eq 10) v out v d + v in --------------------------- 1 1 d ? ------------- = (eq 11) d 1 v in v out v d + --------------------------- ?= (eq 12) i l i out 1 d ? ------------- = (eq 13) i l d d v in f s l ------------------- = ams ag technical content still valid
revision 1.8 16 - 20 as3833 datasheet - d e t a i l e d d e s c r i p t i o n peak current: rms inductor current: this peak current is flowing through mn1 during phase 1 and through d1 during phase 2 of each cycle. therefore this peak current is important for a proper diode , mosfet and inductor selection. note: the saturation current of the inductor should be about 20 to 30% larger than the peak current 8.4.5 input capacitor the input capacitor has to supply the delta inductor current and it should be selected according to: 8.4.6 output capacitor the output capacitor must be chosen according to the max allowable output ripple at high load. 8.4.7 current sense resistor note: low inductance, specific designed current sensing resistors should be used, e.g. stackpole electronics csr/csrn series of sensing resistors with less than 0.2nh (typ.). 8.4.8 compensation network a typical choice for values of the compensation network is c10 = 100pf, c11 = 10nf, r11 = 100k . use these values as initial choice and evaluate the transient response of the system to verify the behavior at output load change. (eq 14) i pk i l i l ? 2 -------- i out 1 d ? ------------- d v in 2 f s l ----------------------- +=+= (eq 15) i rms i l 2 1 12 ------ i l ? ? ? ? ? c in i l ? 4 v in ? f sw ------------------------------------ > (eq 17) esr v in ? 2 i l ? ----------------- < (eq 18) c out i out max ? d v out ? f sw ------------------------------------ > (eq 19) esr v out ? i out 1 d ? ------------- v in d 2 l f sw --------------------------- + ? ? ? ? < (eq 20) r s max ? v sense i l 0 5 , i l ? + ----------------------------------- = (eq 21) p rs i 2 l rms ? r s d = ams ag technical content still valid
revision 1.8 17 - 20 as3833 datasheet - p a c k a g e d r a w i n g s a n d m a r k i n g s 9 package drawings and markings figure 18. tqfp-32 marking table 4. packaging code figure 19. soic-28 marking table 5. packaging code yy ww g zz last two digits of the current year manufacturing week plant identifier free choice / traceability code yy ww r zz last two digits of the current year manufacturing week plant identifier free choice / traceability code ams ag technical content still valid
revision 1.8 18 - 20 as3833 datasheet - p a c k a g e d r a w i n g s a n d m a r k i n g s figure 20. tqfp-32 package ams ag technical content still valid
revision 1.8 19 - 20 as3833 datasheet - p a c k a g e d r a w i n g s a n d m a r k i n g s figure 21. soic-28 package ams ag technical content still valid
revision 1.8 20 - 20 as3833 datasheet - o r d e r i n g i n f o r m a t i o n 10 ordering information the devices are available as the standard products shown in table 6 . n ote: all products are rohs compliant and austriamicrosystems green. buy our products or get free samples online at icdirect: http://www.austriamicrosystems.com/icdirect technical support is available at http://www.austriamicrosystems.com/technical-support for further information and requests, please contact us mailto: sales@austriamicrosystems.com or find your local distributor at http://www.austriamicrosystems.com/distributor table 6. ordering information ordering code marking description delivery form package as3833-ztqt as3833 tape & reel tqfp-32 AS3833-ZSOT as3833 tape & reel soic-28 ams ag technical content still valid

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