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aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 1 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 general description the aat2822-aat2825 family of integrated panel power solutions provides the regulated voltages required by an active-matrix thin-film transistor (tft) liquid-crystal dis - play (lcd). the aat2822 includes a triple-output dc-dc converter, a led backlight driver, and a vcom buffer in a 4 mm x 4mm tqfn package. the primary 1.3mhz dc-dc boost converter uses an ultra-small inductor and ceramic capacitor to generate output voltage (v avdd ) of up to 14.5v for the charge pumps. the low on-resistance of the integrated power mosfet allows for efficiency up to 93%. the two charge pumps independently regulate a positive output (vgh) and a negative output (vgl). these low- power outputs use external diode and capacitor stages to regulate output voltages up to +30v and down to -30v. a proprietary regulation algorithm minimizes out - put ripple when using small capacitors. the high efficiency backlight driver provides a constant current output capable of boosting up to 28v. the driver is an ideal power solution for backlight applications with up to seven white leds in series or up to 39 white leds in a parallel and series configuration. led brightness is pwm controlled up to 1khz. filtered pwm is supported for higher frequencies. the high slew rate operational amplifier is suitable for vcom buffering and gain adjustment. the sequencing of the power supplies ensures proper panel startup and avoid damage to the device. the aat2822 family is available in a pb-free, 24-pin 4 x 4mm tqfn package and operates over the -40c to +85c temperature range. featureslcd bias power ? 2.5v to 5.5v input supply range ? 1.3mhz fixed frequency current-mode step-up regulator ? fast transient response ? adjustable voltage up to 14.5v ? 1% typical accuracy ? small external inductor and capacitors ? integrated soft start and sequencing of all rails ? short-circuit, over-voltage, and over-temperature protection positive output, vgh ? up to 13.2v input supply (v dd ) ? adjustable voltage up to 30v @ 20ma ? 3% typical accuracy negative output, vgl ? up to 13.2v input supply (v dd ) ? adjustable voltage down to -30v @ 20ma ? 3% typical accuracy wled driver ? input voltage range: 2.5v to 25v ? maximum continuous output: ? 12v @ 260ma ? 28v @ 50ma ? panel sizes from 5" C 10" ? 5.0" 3s5p ? 5.6" 3s6p ? 7.0" 3s9p ? 8.0" 3s10p/11p ? 10" 3s13p ? constant led current with 6% accuracy ? pwm dimming control ? up to 1khz ? 1.3mhz switching fixed frequency ? up to 90% efficiency vcom buffer ? high-performance ? 13v/s slew rate ? 12mhz, -3db bandwidth ? 75ma output short-circuit current ? low 1.5ma quiescent current applications? automotive displays ? digital photo frames ? netbooks ? pnds downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 2 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 typical application vi n lx fb co mp drv p fb p fb n drvn re f v gl v avd d r in r fb1 r fb2 c in2 c avddout c drvp c drvn d1 r co mp r fbp1 c in1 c vgh c co mp c wi n c vg l c re f d2 d3 vd d v in v gh v led wl x ov p we n wd im wf b pw m on of f en on of f l2 d2 r bal up to 13 st ring s opin op - ou t op + agnd pgnd1 pgnd 2 wc om p r wc om p c wc om p vavd d vcom _i n vcom _o ut r op1 r op2 c wo ut c comout v in v dd l1 2.5v - 5.5v 2.5v - 5.5v r fbn1 r fbp2 r fbn2 r ovp1 r ovp2 downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 3 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 1. future products. please contact factory for availability. pin descriptions pinout is preliminary and subject to change during development. pin number symbol function description aat2822 aat2823 aat2824 1 aat2825 1 1 1 n/a n/a wlx o boost inductor node. connect an inductor between in and wlx. wlx is high impedance in shutdown. 2 2 2 2 pgnd2 i/o power ground. connect to gnd underneath the ic. 3 3 3 3 ref o internal reference bypass terminal. connect a 0.1f capaci - tor from this terminal to analog ground (gnd). external load capability to 50a. 4 4 4 4 fbn i negative charge-pump regulator feedback input. regulates to 0v nominal. 5 5 n/a n/a wen i active high logic level enable for wled driver. 6 6 6 6 drvn o negative charge-pump driver output. output high level is vdd, and low level is pgnd. 7 7 7 7 vdd pi positive and negative charge-pump driver supply voltage. by - pass to pgnd with a 0.1f capacitor. 8 8 8 8 drvp o positive charge-pump driver output. output high level is vinp, and low level is pgnd. 9 9 9 9 en i active high logic level enable input. connect en to in for normal operation. 10 10 10 10 fbp i positive charge-pump regulator feedback input. regulates to 0.6v nominal. connect feedback resistive divider to analog ground (gnd). 11 11 11 11 pgnd1 i/o power ground. connect to gnd underneath the ic. 12 12 12 12 lx o main boost regulator power mosfet n-channel drain. connect output diode and output capacitor as close to pgnd as possible. 13 13 13 13 comp i step-up regulator error-ampliier compensation point. connect a series rc from comp to agnd. 14 14 14 14 fb o main boost regulator feedback input. regulates to 0.6v nomi - nal. connect feedback resistive divider to analog ground (gnd) to set output voltage. 15 n/a 15 n/a opin i operational-ampliier power input. power supply rail for the operational ampliiers. typically connected to vavdd. bypass opin to gnd with a 0.1f capacitor. 16 n/a 16 n/a op+ i operational-ampliier non-inverting input. 17 n/a 17 n/a op- i operational-ampliier inverting input. 18 n/a 18 n/a out o operational-ampliier output. 19 19 n/a n/a wcomp i white led driver error-ampliier compensation point. connect a series rc from wcomp to agnd. 20 20 n/a n/a wfb o feedback pin. connect a resistor to ground to set the maximum led current. 21 21 n/a n/a ovp o feedback pin for over-voltage protection sense. connect a re - sistive divider between the boost converter output and ground. 22 22 22 22 vin i supply input. +2.5v to +5.5v input range. bypass with a 0.1f capacitor between in and gnd, as close to the pins as possible. 23 23 agnd agnd agnd i/o analog ground. connect to power ground (pgnd) underneath the ic. 24 24 n/a n/a wdim i dimming control input. apply a pwm signal up to 1khz to adjust the wled brightness from 100% to 5%, proportional to the duty cycle of the pwm signal. n/a 15, 16, 17, 18 1, 19, 20, 21 1, 15, 16, 17, 18, 19, 20, 21 n/c not connected. ep ep 5, 24, ep 5, 24, ep gnd ground. ep = exposed paddle, connect to pcb ground plane. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 4 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 pin configurations tqfn44-24 (top view) aat2822 aat2823 1 3 2 5 4 6 18 16 17 14 15 13 10 11 12 8 9 7 19 21 20 23 22 24 wlx pgnd2 ref fbn wen drvn vdd drvp en fbp pgnd1 lx opin op+fb comp op- out ep wcomp wfb ovp vin agnd wdim 1 3 2 5 4 6 18 16 17 14 15 13 10 11 12 8 9 7 19 21 20 23 22 24 wlx pgnd2 ref fbn wen drvn vdd drvp en fbp pgnd1 lx n/c n/cfb comp n/c n/c ep wcomp wfb ovp vin agnd wdim aat2824 aat2825 1 3 2 5 4 6 18 16 17 14 15 13 10 11 12 8 9 7 19 21 20 23 22 24 n/c pgnd2 ref fbn gnd drvn vdd drvp en fbp pgnd1 lx opin op+fb comp op- out ep n/c n/c n/c vin agnd gnd 1 3 2 5 4 6 18 16 17 14 15 13 10 11 12 8 9 7 19 21 20 23 22 24 n/c pgnd2 ref fbn gnd drvn vdd drvp en fbp pgnd1 lx n/c n/cfb comp n/c n/c ep n/c n/c n/c vin agnd gnd downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 5 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at conditions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time. 2. mounted on an fr4 board. 3. derate 20mw/c above 25c. part number descriptions part number lcd bias startup sequence backlight vcom buffer aat2822 ? vavdd->vgh->vgl ? ? aat2822-1 ? vavdd->vgl->vgh ? ? aat2823 ? vavdd->vgh->vgl ? aat2823-1 ? vavdd->vgl->vgh ? aat2824 ? vavdd->vgh->vgl ? AAT2824-1 ? vavdd->vgl->vgh ? aat2825 ? vavdd->vgh->vgl aat2825-1 ? vavdd->vgl->vgh absolute maximum ratings 1 description value units v in , en -0.3 to 7 v v dd , opin, out, op+, op- -0.3 to 15 lx, wlx -0.3 to 30 wcomp, comp, fb, fbp, fbn, ref, wen, pwm, wfb, ovp -0.3 to v in + 0.3 drvp -0.3 to (v dd + 0.3) drvn -0.3 to (v dd + 0.3) thermal information 2 symbol description value units ja thermal resistance 3 50 c/w p d maximum power dissipation 2 w t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads) 300 downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 6 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 electrical characteristics v in = 5v, en = wen = wdim = v in , v avdd = v dd = 12v, t a = -40c to 85c unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units power supply v in input voltage range 2.5 5.5 v v uvlo under-voltage lockout threshold rising edge 2.4 2.5 v uvlo hys uvlo hysteresis 50 mv i in in quiescent current v fb = v fbp = 0.7v, v fbn = -0.1, lx not switching 1.1 1.6 ma i shdn shutdown current en = wen = low, i shdn = i in + i dd , v dd = 5v 1 a v ref ref output voltage no load 1.182 1.20 1.218 v ref load regulation 0 < i load < 50a 10 mv ref current in regulation 50 a t sd thermal shutdown temperature rising +140 o c hysteresis 15 main step-up regulator v avdd output voltage range v in - v diode 14.5 v f osc operating frequency 910 1300 1690 khz dc max maximum duty cycle 86 90 % v fb fb regulation voltage no load 0.588 0.6 0.612 v fb fault trip level v fb falling 0.535 0.546 0.557 v fb load regulation 0 < i avdd < full load 0.01 %/ma fb line regulation v in = 2.5v to 5.5v 0.1 0.4 %/v fb input bias current v fb = 0.7v -1 +1 a r lx(on) lx on-resistance i lx = 200ma 350 700 m? i lx lx leakage current v lx = 13.2v 0.01 20 a i lim lx current limit v fb = 0.7v, duty cycle = 75% 1 a t ss soft-start period 1.3 ms gate high charge pump (vgh) v dd v dd input supply range 2.7 13.2 v operating frequency f osc khz v fbp fbp regulation voltage 0.588 0.6 0.612 v fbp fault trip level v fbp falling 470 530 mv i fbp fbp input bias current v fbp = 0.7v -1 +1 a drvpp rds drvp pch on-resistance 3 6 ? drvpn rds drvp nch on-resistance v fbp = 0.585v 1.5 3 v fbp = 0.615v 20 k gate low charge pump (vgl) v dd v dd input supply range 2.7 13.2 v operating frequency f osc hz v fbn fbn regulation voltage -50 0 +50 mv fbn fault trip level v fbn rising 408 425 442 mv i fbn fbn input bias current v fbn = -0.1v -1 +1 a drvnp rds drvn pch on-resistance 3 6 ? drvnn rds drvn nch on-resistance v fbn = 0.035v 1.5 3 ? v fbn = -0.025v 20 k? downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 7 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 electrical characteristicsv in = 5v, en = wen = wdim = v in , v avdd = v dd = 12v, t a = -40 o c to 85 o c unless otherwise noted. typical values are at t a = 25 o c. symbol description conditions min typ max units wled driver (aat2822, aat2823 only) v led output voltage v in - v diode 28 v i out maximum continuous output current v led = 28v 50 ma v fb / v in line regulation v in = 2.5v to 5.5v 0.7 %/v r ds(on) low side switch on-resistance 300 m v wfb wfb pin regulation 0.282 0.3 0.318 v t ss soft-start time from enable to output regulation; v fb = 300mv 300 s v ovp over-voltage protection threshold v led rising 0.55 0.60 0.65 v ov hys over-voltage hysteresis v led falling 25 mv i limit n-channel current limit 1.3 a f pwm maximum w dim pwm frequency 1 khz dc min minimum duty cycle 5 % vcom buffer (aat2822 , aat2824 only) v opin supply range 4.5 13.2 v i opin supply current 1.5 2.5 ma v os input offset voltage (v neg , v pos , v out ) v sup /2 12 mv v cm input common-mode range 0 v sup v v oh output voltage swing, high i out = 5ma v sup - 150 mv v ol output voltage swing, low i out = -5ma 150 mv i sc short-circuit current v sup /2 source 75 ma sink 75 gbw gain bandwidth product 12 mhz sr slew rate 13 v/s logic wdim/ wen l /en l enable input low voltage v in = 2.5v 0.4 v wdim/ wen h /en h enable input high voltage v in = 5.5v 1.4 v i en wdim/wen/en input current 1 a downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 8 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 typical characteristics oscillator frequency vs. temperature temperature (c) oscillator frequency (mhz) -4 0- 15 10 35 60 85 1.235 1.240 1.245 1.250 1.255 1.260 1.265 1.270 1.275 1.280 1.285 power up sequencing (vavddvghvgl; v in = 5.0v) ie (500i) ns(5vi) v avdd (5vi) v gl (0vi) v gh (0vi) power up sequencing (vavdd->vgl->vgh; v in = 5.0v) time (1ms/div) en/set(2v/div) v avdd (2v/div) v gl (10v/div) v gh (10v/div) main boost efficiency (v out = 12v) output current (ma) efficiency (%) 05 0 100 200 150 300 250 400 350 500 450 0 10 20 30 40 50 60 70 80 90 100 main boost load transient (v in = 5.0v) time (500s/div) v out (100mv/div) i out (50ma/div) 100ma 10ma line regulation input voltage (v) output voltage (v) 2. 73 .7 3. 24 .7 4. 25 .2 11.75 11.80 11.85 11.90 11.95 12.00 12.05 12.10 12.15 12.20 12.25 i out = 1ma i out = 10ma i out = 100ma downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 9 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 typical characteristics vgh vs. temperature temperature (c) vgh (v) -4 0- 15 10 35 60 85 29.5 29.6 29.7 29.8 29.9 30.0 30.1 30.2 30.3 30.4 30.5 vgh load regulation load current (ma) positive output voltage (v) 02 48 61 2 10 16 14 20 18 29.5 29.6 29.7 29.8 29.9 30.0 30.1 30.2 30.3 30.4 30.5 5.0v2.7v vgl vs. temperature temperature (c) vgl (v) -4 0- 15 10 35 60 85 -30.50 -30.40 -30.30 -30.20 -30.10 -30.00 -29.90 -29.80 -29.70 -29.60 -29.50 vgl load regulation load current (ma) negative output voltage (v) 02 48 61 2 10 16 14 20 18 -30.5 -30.4 -30.3 -30.2 -30.1 -30.0 -29.9 -29.8 -29.7 -29.6 -29.5 5.0v2.7v wled efficiency vs. load current (7s3p; v in = 5v; v l = 12v) load current (ma) efficiency (%) 01 02 04 0 30 60 50 80 70 100 90 0 10 20 30 40 50 60 70 80 90 wled operation at 300ma load (v in = 5.0v, 3s13p) time (200s/div) v led (5v/div) i led (500ma/div) v out (100mv/div) downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 10 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 typical characteristics vcom buffer supply current vs. temperature (v in = 5.0v, v opin = 12v) temperature (c) vgl (v) -4 0- 15 10 35 60 85 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 vcom input offset voltage vs. temperature (v in = 5.0v, v opin = 12v) temperature (c) input offset voltage (mv) -4 0- 15 10 35 60 85 0.0 0.5 1.0 1.5 2.0 2.5 downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 11 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 functional block diagram aat2822 step-up controller charge pump control reference op wled control vdd fbn ref vin comp lx fbdrvp fbp drvn wfb opin op- out op+ brightness control ovp wlx we n wdim en wcomp agnd pgnd1 pgnd2 functional description main boost converter the main boost regulator contains a current-mode, fixed-frequency pwm architecture to maximize loop bandwidth and provide fast transient response to pulsed loads typical of tft-lcd panel source drivers. the 1.3mhz switching frequency allows the use of low profile, low value inductors and ceramic capacitors to minimize the thickness of lcd panel designs. dual charge-pump regulator the aat2822 provides low-power regulated output volt - ages from two individual charge pumps to provide the vgh and vgl supplies. using a single stage, the vgl charge pump inverts the supply voltage (v dd ) and pro - vides a regulated negative output voltage. the vgh charge pump doubles v dd and provides a regulated posi - tive output voltage. these outputs use external schottky diodes and capacitor multiplier stages (dependent upon the required output voltage) to regulate up to 30v. integrated soft-start circuitry minimizes the start-up inrush current and eliminates output voltage overshoot across the full input voltage range and all load condi - tions. a constant switching frequency of 1.3mhz mini - mizes output ripple and capacitor size. white led backlight applications the aat2822 consists of a 1.3mhz fixed-frequency dc/ dc boost controller, and an integrated high voltage mosfet power switch. a high-voltage rectifier, power downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 12 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 inductor, output capacitor, and sense resistors are required to implement a dc/dc constant current boost converter. integrated soft-start circuitry minimizes the start-up inrush current and eliminates output voltage overshoot across the full input voltage range and all load conditions. the backlight current is set by an external ballast resistor up to a maximum of 260ma at 12v or 50ma at 28v output. brightness control is via pwm dim - ming at up to 1khz. higher frequencies are achieved by filtered pwm. the aat2822 can drive from 3 leds in series up to a maximum of 7 leds, making it suitable for screen sizes from 5 up to 10. depending upon the number of leds required, up to 9 parallel strings can be successfully driven. if the ovp input voltage is exceeded the wled driver continues to regulate at the ovp threshold. start en high wled boost stop switching v wled >v ovp no yesyes no figure 1: wled driver operation. vcom buffer: operational amplifier the operational amplifier drives the lcd backplane vcom. the operational amplifier features +/- 75ma(min) output short-circuit current, 13v/s slew rate, and 12mhz bandwidth. internal short-circuit protection limits the short circuit current while the output is directly shorted. power supply sequencing the aat2822 family has integrated power supply sequenc - ing to prevent damage to the lcd screen. two sequences are available to swap the startup of the positive and negative gate drive voltages. the startup sequence for the -1 option establishes main boost supply (v avdd ) first, followed by the gate voltages vgl then vgh. the sequence for the plain option is to establish v avdd first followed by vgh then vgl. the wled backlight driver is independently controlled by wen and wdim. operating faults the aat2822 family continuously monitors for fault con - ditions on the main boost converter and charge pumps according to defined fault trip levels. during operation if any fault conditions persist the controller will shut down all supplies. after removing the fault conditions, recycle the enables to start up the supplies. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 13 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 start en high main boost v fb > fb fault trip level and persist negative cp v fbn > fbn fault trip level and persist positive cp v fbp > fbp fault trip level and persist star t- up sequence complete shut-down main boost, negative cp, and positive cp yes no yesyes yes nono no no en low opamp figure 2: startup sequence for aat282x-1 1 . 1. for aat282x the startup sequence is positive charge pump followed by the nega - tive charge pump. application informationmain step-up converter output capacitor the high output ripple inherent in the boost converter necessitates low impedance output filtering. multi-layer ceramic (mlc) capacitors provide small size and ade - quate capacitance, low parasitic equivalent series resis - tance (esr) and equivalent series inductance (esl), and are well suited for use with the primary step-up con - verter. mlcs of type x7r or x5r are recommended to ensure good capacitance stability over the full operating temperature range. the output capacitor is sized to maintain the output load without significant voltage droop during the power switch on interval, when the output diode is not con - ducting. and because the vgh, vgl also have their input power from the main step-up converter output, the out - put capacitor may also decrease the inrush current dur - ing vgh and vgl start up. a ceramic output capacitor with a minimum value of 22f is recommended. for inrush current sensitive applications, two 22f are rec - ommended. typically, 25v rated ceramic capacitors are required for the 24v boost output. ceramic capacitors sized as small as 0805 are available which meet these requirements. mlcs exhibit significant capacitance reduction with applied voltage. output ripple measure - ments should confirm that output voltage droop is acceptable. input capacitor the boost converter input current flows during both on and off switching intervals. the input ripple current is less than the output ripple and, as a result, less input capacitance is required. however, the aat2822 input voltage is shared among other channels; a ceramic input capacitor from 4.7f to 10f is recommended. minimum 6.3v rated ceramic capacitors are required at the input. ceramic capacitors sized as small as 0603 are available which meet these requirements. large capacitance tantalum or solid-electrolytic capaci - tors may be necessary to meet stringent output ripple and transient load requirements. these can replace (or be used in parallel with) ceramic capacitors. both tanta - lum and oscon-type capacitors are suitable due to their low esr and excellent temperature stability (although they exhibit much higher esr than mlcs). aluminum- electrolytic types are less suitable due to their high esr downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 14 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 characteristics and temperature drift. unlike mlcs, these types are polarized and proper orientation on input and output pins is required. 30% to 70% voltage derating is recommended for tantalum capacitors. selecting the schottky diode to ensure minimum forward voltage drop and no recov - ery, high voltage schottky diodes are the best choice for the primary step-up converter. the output diode is sized to maintain acceptable efficiency and reasonable operat - ing junction temperature under full load operating condi - tions. forward voltage (v f ) and package thermal resis - tance ( ja ) are the dominant factors to consider in select - ing a diode. the diodes published current rating may not reflect actual operating conditions and should be used only as a comparative measure between similarly rated devices. 20v rated schottky diodes are recommended for outputs less than 15v, while 30v rated schottky diodes are recommended for outputs greater than 15v. the average diode current is equal to the output cur - rent: i avg < i out the average output current multiplied by the forward diode voltage determines the loss of the output diode. p loss_diode = i avg v f = i out v f diode junction temperature can be estimated: t j = t a + ja p loss_diode the junction temperature should be maintained below 110c, but may vary depending on application and/or system guidelines. the diode ja can be minimized with additional pcb area on the cathode. pcb heat sinking the anode may degrade emi performance. the reverse leakage current of the rectifier must be con - sidered to maintain low quiescent (input) current and high efficiency under light load. the rectifier's reversed current increases dramatically at high temperatures. selecting the main step-up inductor the primary step-up converter is designed to operate with a 2.2h inductor for all input and output voltage combinations. the inductor saturation current rating should be greater than the nmos current limit. if neces - sary, the peak inductor current can exceed the satura - tion level by a small amount with no significant effect on performance . the maximum duty cycle can be estimated from the relationship for a continuous mode boost con - verter. maximum duty cycle (d max ) is the duty cycle at minimum input voltage (v in(min) ) . d max = (v out + v f - v in(min) ) v out + v f where v f is the schottky diode forward voltage and can be estimated at 0.5v. manufacturers specifications list both the inductor dc current rating, which is a thermal limitation, and peak inductor current rating, which is determined by the saturation characteristics. measurements at full load and high ambient temperature should be completed to ensure that the inductor does not saturate or exhibit excessive temperature rise. the output inductor (l) is selected to avoid saturation at minimum input voltage, maximum output load condi - tions. peak current may be calculated from the following equation, again assuming continuous conduction mode. worst-case peak current occurs at minimum input volt - age (maximum duty cycle) and maximum load. switching frequency (f s ) is at 1.3mhz with a 2.2h inductor. i peak = + i out 1 - d max d max v in(min) 2 f s l the rms current flowing through the boost inductor is equal to the dc plus ac ripple components. under worst-case rms conditions, the current waveform is critically continuous. the resulting rms calculation yields worst-case inductor loss. the rms value should be compared against the manufacturers temperature rise or thermal derating guidelines. i peak 3 i rms = for a given inductor type, smaller inductor size leads to an increase in dcr winding resistance and, in most cases, increased thermal impedance. winding resistance degrades boost converter efficiency and increases the inductor operating temperature. p loss_inductor = i rms 2 dcr setting the output voltage the resistive divider network r2 and r3 of figure 7 pro - grams the output to regulate at a voltage higher than 0.6v as shown in table 1. to limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the minimum sug - downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 15 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 gested value for r3 is 6.04k. the resistive divider can be calculated in the following equation: r 3 = r 2 -1 = r 2 - 1 v avd d v fb v avd d 0.6v v avdd (v) r 3 = 6.04k? r 2 (k?) r 3 = 59k? r 2 (m?) 9 84.5 0.825 10 93.1 0.931 11 105 1.02 12 115 1.13 13 124 1.21 15 143 1.4 20 196 1.1 22 215 2.1 24 237 2.3 table 1: setting the output voltage for the main step-up converter. selecting compensation components the aat2822 main boost architecture uses peak current mode control to eliminate the double pole effect of the output l&c filter and simplifies compensation loop design. the current mode control architecture simplifies the transfer function of the control loop to a one-pole, one left plane zero and one right half plane (rhp) sys - tem in frequency domain. the dominant pole can be calculated by: f p = 1 2 r o c 6 the esr zero of the output capacitor can be calculated by: f z_esr = 1 2 r esr c 6 where:c 6 is the output filter capacitor r o is the load resistor value r esr is the equivalent series resistance of the output capacitor. the right half plane (rhp) zero can be determined by: f z_rhp = v in 2 2 l 1 i avdd v avdd it is recommended to design the bandwidth to one decade lower than the frequency of rhp zero to guaran - tee the loop stability. a series capacitor and resistor network (r11 and c8) connected to the comp pin sets the pole and zero which are given by: f p_com = 1 2 r ea c 8 f z_com = 1 2 r 11 c 8 where:c 8 is the compensation capacitor r 11 is the compensation resistor r ea is the output resistance of the error amplifier (m). a 100pf capacitor and a 200k resistor in series are chosen for optimum phase margin and fast transient response. charge pump the number of charge pump stages required for a given output (v gh ) varies with the input voltage applied (v avdd ) from the main boost. a lower input voltage requires more stages for a given output. if the numbers of stag - es increases, the maximum load current limitation of the charge pump would be decreased to maintain output voltage regulation. the number of stages required can be estimated by: v gh - v avdd(min) v avdd(min) - 2v f n p = for the positive output and v gl 2v f - v avdd(min) n n = for the negative output where v f = 0.31v is the forward voltage of the bat54 schottky diode at 4ma forward current. when solving for n p and n n , round up the solution to the next highest integer to determine the number of stages required. negative output voltage (v gl ) the negative output voltage is adjusted by a resistive divider from the output (v on ) to the fbn and ref pins. the maximum reference voltage current is 200a; therefore, the minimum allowable value for r 10 of figure downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 16 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 6 is 6.04k ? . it is best to select the smallest value pos - sible for r 10 , as this will keep the value of r 9 to a mini - mum. with r 10 selected, r 9 can be determined: r 9 = r 10 = r 10 v gl v re f v gl 1.2v positive output voltage (v gh ) the positive output voltage is set by a resistive divider from the output (v gh ) to the fbp and ground pins. limiting the value of r 7 to 6.04k ? or lower reduces noise in the feedback circuit. once r 7 has been determined, solve for r 6 : r 6 = r 7 - 1 = r 7 - 1 v gh v fb p v gh 0.6v flying and output capacitors the minimum value for the flying capacitor is limited by the output power requirement, while the maximum value is set by the bandwidth of the power supply. if c fly is too small, the output may not be able to deliver the power demanded, while too large of a capacitor may limit the bandwidth and time required to recover from load and line transients. a 0.1f x7r or x5r ceramic capacitor is typically used. the voltage rating of the flying and reser - voir output capacitors varies with the number of charge pump stages. the reservoir output capacitor value should be roughly 10 times the value of the flying capacitor. use larger capacitors for reduced output ripple. input capacitor the primary function of the input capacitor is to provide a low impedance loop for the edges of pulsed current drawn by the ic. a low esl x7r or x5r type ceramic capacitor is ideal for this function. the size required will vary depending on the load, output voltage, and input voltage characteristics. typically, the input capacitor value should be 5 to 10 times the value of the flying capacitor. if the source impedance of the input supply is high, a larger capacitor may be required. to minimize stray inductance, the capacitor should be placed as closely as possible to the ic. this keeps the high fre - quency content of the input current localized, minimizing radiated and conducted emi. rectifier diodes for the rectifiers, use schottky diodes with a voltage rat - ing of 1.5 times the input voltage. the maximum steady- state voltage seen by the rectifier diodes for both the positive and negative charge pumps (regardless of the number of stages) is: v reverse = v in - v f the bat54sdw quad schottky diode in a sot363 (2x2mm) package is a good choice for multiple-stage charge pump configuration. white led driver the white led backlight driver can be enabled when input supply rises above under voltage lockout threshold. to reduce inrush current it is recommended that the main boost and white led driver are not enabled concurrently. over-voltage protection (ovp) with open circuit failure the ovp protection circuit consists of a resistor network tied from the output voltage to the ovp pin (see figure 3). to protect the device from open circuit failure, the resistor divider can be selected such that the over-volt - age threshold occurs prior to the output reaching v led+(max) . the value of r 5 should be selected from 10k to 20k to minimize losses without degrading noise immunity. r 4 = r 5 -1 = 10k -1 v led+(max) v ov p v led+(max) 0.6v wl x ov p wf b r 8 c 4 c 5 d 2 l 2 r 4 r 5 0.6v 0.3v v in v wl x v le d figure 3: over-voltage protection circuit. ovp constant voltage operation under closed loop constant current conditions, the output voltage is determined by the operating current, led for - ward voltage characteristics (v fled ), quantity of series connected leds (n), and the feedback pin voltage (v fb ). v out = v fb + n v fled downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 17 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 when the rising ovp threshold is exceeded, switching is stopped and the output voltage decays. switching auto - matically restarts when the output drops below the lower ovp hysteresis voltage (100mv typical), and as a result the output voltage increases. the cycle repeats, maintaining an average dc output voltage proportional to the average of the rising and falling ovp levels (mul - tiplied by the resistor divider scaling factor). high oper - ating frequency and low output voltage ripple ensure dc current and negligible flicker in the led string(s). while ovp is active, the maximum led current program - ming error (i led ) is proportional to voltage error across an individual led (v fled ). ?v fled = n v fled(typ) - v ovp(min) - v wfb n to minimize the i led error, the minimum ovp voltage (v ovp(min) ) may be increased, yielding a corresponding increase in the maximum ovp voltage (v ovp(max) ) . measurements should confirm that the maximum switch - ing node voltage (v wlx(max) ) is less than 30v under worst case operating conditions. v wlx(max) = v ovp(max) + 1 + v f + v ring r 2 r 1 v f is the schottky diode d 2 forward voltage at turn-off. v ring is the voltage ring occurring at turn-off. white led selection and current setting the wled current is controlled by the wfb voltage and the ballast resistor (r 8 ). for maximum accuracy, a 1% tolerance resistor is recommended. the ballast resistor (r 8 ) value can be calculated as fol - lows: r 8 = v wfb(max) i led(max) where v wfb = 0.3v for example, if the maximum current for each string of 3 series leds is 20ma, the maximum current for a 10 inch panel (3s13p) is 260ma (20ma x 13), which cor - responds to a minimum resistor value of 1.15 ? r 8 = = 1.15 0.3v 260ma maximum i led current (ma) r 8 ( ? ) 30 0.768 25 0.909 20 1.15 15 1.54 10 2.32 5 4.64 table 2: maximum led current and ballast resistor (r 8 ) values for 10 panel size. typical white leds are driven at maximum continuous currents of 15ma to 20ma. the maximum number of series-connected leds is determined by the minimum output voltage of the boost converter (v led ), minus the maximum feedback voltage (v wfb(max) ) divided by the maximum led forward voltage (v fled(max) ) which can be estimated from the manufacturers datasheet at the maximum led operating current. v le d = v ovp(typ) + 1 r 5 r 4 n = v ovp(min) - v wfb(max) v fled(max) for example, the typical forward voltage of the white led is 3.5v at 20ma. v le d = v ovp(typ) = 0.6v = 27.8v + 1 r 5 r 4 + 1 464k 10k n = = = 7.8 leds v ovp(min) - v wfb(max) v fled(max) 27.8v - 0.6v 3.5v therefore, under these typical operating conditions, 7 leds can be used in series for each string. pwm dimming control the dimming of the white led can be controlled using a pwm or a filter pwm signal. by connecting a pwm signal to the wdim pin and adjusting the duty cycle of the pwm signal, the dimming of the white led changes proportion - ally to the percentage of the duty cycle as shown in figure 4. however, the dimming control using pwm connected to the wdim pin can operate at a frequency up to 1khz. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 18 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 wdim 24 wlx 1 wcomp 19 en 9 agnd 23 pgnd2 2 wen fbp 10 ovp 21 drvp 8 vdd 7 wfb 20 n/c 16 n/c 15 pgnd1 11 lx 12 comp 13 fb 14 n/c 17 n/c 18 vin 22 3 fbndrvn aat2822 adj r8 r210 pwm figure 4: pwm dimming control. for applications requiring a pwm frequency higher than 1khz, an external filter pwm is connected to the wfb pin to control the dimming of the white led. this low-pass filter (r 23 /c 25 ) integrates the high frequency pwm signal to produce a dc dimming control as shown in figure 5. wdim 24 wlx 1 wcomp 19 en 9 agnd 23 pgnd2 2 wen fbp 10 ovp 21 drvp 8 vdd 7 wfb 20 n/c 16 n/c 15 pgnd1 11 lx 12 comp 13 fb 14 n/c 17 n/c 18 vin 22 3 fbn drvn aat2822 adj r8 4.99 k r2 1 hf-pwm r23 4.99k r22 28k c25 0.1f connect wdim to vin figure 5: low-pass filter pwm dimming control. when the pwm duty cycle is adjusted, the dc voltage across the ballast resistor (r 8 ) changes, resulting in change of the white led current. apply the kcl at the feedback node (wfb). the voltage across the r 8 resistor can be expressed: r 21 r 22 v r8 = 0.3v - (v c25 - 0.3v) for minimum dimming, v r8 = 0v. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 19 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 choose r 21 = 4.99k and v c25 = 2v, and solve for r 22 : r 21 (0.3v - v r8 ) (v c25 - 0.3v) r 22 = = 28k the low-pass filter should be chosen to produce an acceptable ripple for the dc dimming voltage and a small time constant. for application where the pwm fre - quency is greater than 10khz, the optimum values for the low-pass filter are r 23 = 4.99k and c 25 = 0.1f. selecting the schottky diode to ensure minimum forward voltage drop and no recov - ery, high-voltage schottky diodes are considered the best choice for the wled boost converter. the output diode is sized to maintain acceptable efficiency and rea - sonable operating junction temperature under full load operating conditions. forward voltage (v f ) and package thermal resistance ( ja ) are the dominant factors to con - sider in selecting a diode. the diode's non-repetitive peak forward surge current rating (i fsm ) should be con - sidered for high pulsed load applications such as camera flash. the i fsm rating drops with increasing conduction period. manufacturers datasheets should be consulted to verify reliability under peak load conditions. the diodes published current rating may not reflect actual operating conditions and should be used only as a com - parative measure between similarly rated devices. 40v rated schottky diodes are recommended for outputs less than 30v, while 60v rated schottky diodes are rec - ommended for outputs greater than 35v. the average diode current is equal to the output cur - rent: i avg = i out the average output current multiplied by the forward diode voltage determines the loss of the output diode. p loss_diode = i avg v f = i out v f diode junction temperature can be estimated: t j = t a + ja p loss_diode output diode junction temperature should be maintained below 110c, but may vary depending on application and/or system guidelines. the diode ja can be mini - mized with additional pcb area on the cathode. pcb heat-sinking the anode may degrade emi performance. the reverse leakage current of the rectifier must be con - sidered to maintain low quiescent (input) current and high efficiency under light load. the rectifier's reverse current increases dramatically at elevated temperatures. selecting the wled step-up inductor the wled step-up converter has the same topology as the main step-up converter. it is designed to operate with a 2.2h inductor for all input and output voltage combinations. the inductor saturation current rating should be greater than the nmos current limit. d max = (v out + v f - v in(min) ) v out + v f the output inductor (l) is selected to avoid saturation at minimum input voltage and maximum output load con - ditions. peak current may be calculated from the follow - ing equation, again assuming continuous conduction mode. worst-case peak current occurs at minimum input voltage (maximum duty cycle) and maximum load. switching frequency is estimated at 1.3mhz with a 2.2h inductor. i peak = + i out 1 - d max d max v in(min) 2 f s l selecting the wled step-up capacitors the high output ripple inherent in the boost converter necessitates low impedance output filtering. multi-layer ceramic (mlc) capacitors provide small size and adequate capacitance, low parasitic equivalent series resistance (esr) and equivalent series inductance (esl), and are well suited for use with the wled boost regulator. mlc capacitors of type x7r or x5r are recom - mended to ensure good capacitance stability over the full operating temperature range. the output capacitor is sized to maintain the output load without significant voltage droop ( v out ) during the power switch on interval, when the output diode is not conducting. a ceramic output capacitor with a value of 2.2f to 4.7f is recommended. typically, 50v rated capacitors are required for the 28v maximum boost out - put. ceramic capacitors sized as small as 0805 or 1206 are available which meet these requirements. mlc capacitors exhibit significant capacitance reduction with applied voltage. output ripple measurements should confirm that output voltage droop and operating stability are acceptable. voltage derating can minimize this factor, but results may vary with package size and among specific manufacturers. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 20 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 the output capacitor size can be estimated using the equation: i out d max f s ?v out c out = to maintain stable operation at full load, the output capacitor should be sized to maintain v out b etween 100mv and 200mv. the wled boost converter input current flows during both on and off switching intervals. the input ripple current is lower than the output ripple and, as a result, a lower input capacitance is required. lcd vcom buffer the vcom buffer is designed to drive the voltage on the backplane of an lcd display. the buffer must be capable of sinking and sourcing capacitive pulse current at low frequency. a 10nf ceramic output capacitor in series with a 100 resistor is sufficient for buffer stability at high frequencies. the vcom output voltage is typically set to half of the main boost output voltage v add . the maximum input bias voltage for the vcom buffer (v opin ) cannot exceed 13v. in applications where the main boost output voltage v vadd is greater than 13v, v opin should be connected to an exter - nal supply to prevent damage to the device; the jumper j 7 should be left open to disconnect v avdd from v opin . downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 21 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 d1 100p f c8 200k? r1 1 4. 7 f 10 vc 1 vi n wd im 24 wlx 1 wc om p 19 en 9 agnd 23 pgnd2 2 we n 5 fb p 10 ov p 21 drv p 8 vd d 7 wf b 20 op + 16 opin 15 pgnd 1 11 lx 12 comp 13 fb 14 op - 17 ou t 18 vi n 22 re f 3 fb n 4 drv n 6 u1 aat282 2 10f 10 v c3 0.22f 6.3v c7 0.1 f 25 v c1 2 0. 22f 50 v c2 1 pw m 2.2 h l2 ad j r2 6.04 k? r3 22 f 25 v c6 8n f c9 d2 2.2 f 50 v c5 adj r4 10k? r5 6.04 k? r1 0 ad j r6 6.04 k? r7 10k? r1 4 10k? r1 3 17.4 k? r1 2 0? r1 adj r8 0.1 f 50 v c1 3 0. 22f 25 v c1 8 0.1 f 50 v c1 1 0.1 f 25 v c1 0 0.22f 25 v c1 6 0. 22f 50 v c1 9 0.22f 50 v c1 7 j1 vi n en lx vavd d vgh (positive) vgl (negative ) j2 vi n j3 we n ad j r9 0.1 f 10 vc 2 wl x 10f 16 v c4 2.2 h l1 ov p ov p 0? r1 5 agnd vd d 3 4 5 6 2 1 a1 bat54sdw vd d open r1 6 3 4 5 6 2 1 a2 bat54sd w 0.1 f 50 v c1 4 0.1 f 50 v c1 5 3 4 5 6 2 1 a3 bat54sd w 0. 22f 50 v c2 0 1 2 st age 3 j5 1 2 stage 4 j6 0. 1 f c2 2 drv n drv p fb p fb n 0.1 f 25 v c2 3 100? r1 7 10nf c2 4 1 2 st age 2 j4 vi n vin-wled open r1 9 0? r1 8 vavdd 0? r2 1 vi n 0? r2 0 hf-pwm open r2 3 open r2 2 wf b ope n c2 5 3 4 5 6 2 1 a4 bat54sdw 0.1 f 50 v c2 7 0.1 f 50 v c2 8 1 2 st age 2 j8 1 2 st age 3 j9 1 2 st age 4 j1 0 0.22f 50 v c2 9 0.22f 50 v c3 0 avdd vi n vopi n 1 2 j7 10pf 25 v c2 6 wled + wl ed - 1. 2v 0. 6v 0.6v 0.6v 0v figure 6: aat2822ibk evaluation board schematic. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 22 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 component part number description manufacturer u1 aat2822ibk tft-lcd dc-dc converter with wled driver and vcom buffer skyworks c1 grm188r61a475k cap ceramic 4.7f 0603 x5r 10v 10% murata c2 grm188r71c104k cap ceramic 0.1f 0603 x7r 16v 10% c3, c4 grm21br61c106k cap ceramic 10f 0805 x5r 16v 10% c5 grm31cr71h225k cap ceramic 2.2f 1206 x7r 50v 10% c6 grm31cr61c226m cap ceramic 22f 1206 x5r 16v 20% c7 grm188r71a224k cap ceramic 0.22f 0603 x7r 10v10% c8 grm1885c1h101j cap ceramic 100pf 0603 cog 50v 5% c9 grm2195c1h822j cap ceramic 8nf 0805 x7r 50v 10% c10, c12, c22, c23 grm188r61e104k cap ceramic 0.1f 0603 x5r 25v 10% c11, c13, c14, c15, c27, c28 grm188r71h104k cap ceramic 0.1f 0603 x7r 50v 10% c16, c18 grm188r61e224k cap ceramic 0.22f 0603 x5r 25v10% c17, c19, c20, c21, c29, c30 grm21br71h224k cap ceramic 0.22f 0805 x7r 50v10% c24 grm188r71h103k cap ceramic 10nf 0603 x7r 50v 10% c25 nc c26 grm1885c1h100j cap ceramic 10pf 0603 cog 50v 5% a1, a2, a3, a4 bat54sdw-7-f schottky diode array 30v sc70-6 diode inc d1, d2 ss16l schottky diode 1a 60v micro smp taiwan semiconductor l1, l2 cdrh5d16-2r2 power inductor 2.2h 3.0a smd sumida r2, r4, r6, r8, r9 adjustable value (see equations.1 C 5 and table 5); 0603 yageo r3, r7, r10 rc0603fr-0760k4l res 6.04k 1/10w 1% 0603 smd r5, r13, r14 rc0603fr-0710kl res 10k 1/10w 1% 0603 smd r11 rc0603fr-07200kl res 200k 1/10w 1% 0603 smd r12 rc0603fr-0717k4l res 17.4k 1/10w 1% 0603 smd r15, r19, r20, r21 rc0603fr-070rl res 0 1/10w 1% 0603 smd r17 rc0603fr-07100rl res 100 1/10w 1% 0603 smd r18, r22, r23, r25 nc table 3: aat2822ibk evaluation board bill of materials (bom). panel sizes (inches) wled matrix (series and parallel) ballast resistor r 8 () 5 3s5p 2.37 5.6 3s6p 2.0 7 3s9p 1.3 8 3s10p/11p 1.2 10 3s13p 1.0 5 7s2p 4.7 table 4: ballast resistor selection for different panel sizes. eq. 1: r 2 = r 3 -1 = 6.04k -1 v avd d v fb v avd d 0.6v eq. 2: r 9 = r 10 = 6.04k v gl v fb n v gl 1.2v eq. 3: r 6 = r 7 - 1 = 6.04k - 1 v gh v fb p v gh 0.6v downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 23 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 eq. 4: r 4 = r 5 -1 = 10k -1 v led+(max) v ov p v led+(max) 0.6v eq. 5: r 8 = = v wfb(max) i led(max) 0.3v i led(max) d1 100p f c8 200k ? r11 4.7 f 10v c1 vin wdim 24 wlx 1 wcomp 19 en 9 agnd 23 pgnd 2 2 wen 5 fbp 10 ovp 21 drvp 8 vdd 7 wfb 20 n/c 16 n/c 15 pgnd1 11 lx 12 co mp 13 fb 14 n/c 17 n/c 18 vi n 22 ref 3 fbn 4 dr vn 6 u1 aat2823 10f 10v c3 0.22f 6.3v c7 0.1 f 25v c12 0.22f 50 v c21 pwm 2.2 h l2 adj r2 6.04k? r3 22 f 25v c6 8nf c9 d2 2.2 f 50 v c5 adj r4 10k? r5 6.04k? r10 adj r6 6.04k? r7 17.4k? r12 0? r1 adj r8 0.1 f 50v c13 0.22f 25v c18 0.1 f 50 v c11 0.1 f 25 v c10 0.22f 25v c16 0.22f 50v c19 0.22f 50v c17 j1 vin en lx vavd d vg h (positive) vgl (negative) j2 vin j3 wen ad j r9 0.1 f 10v c2 wlx 10f 16v c4 2.2 h l1 ov p ovp agnd vdd 3 4 5 6 2 1 a1 bat54s dw vdd 3 4 5 6 2 1 a2 bat54sd w 0.1 f 50v c14 0.1 f 50v c15 3 4 5 6 2 1 a3 bat54sd w 0.22f 50 v c20 1 2 stage 3 j5 1 2 stage4 j6 drvn drvp fbp fbn 0. 1 f 25 v c23 1 2 stage 2 j4 vin vin-wled open r19 0? r18 vavdd 0? r21 vin 0? r2 0 hf-pwm open r2 3 open r22 wfb open c25 3 4 5 6 2 1 a4 bat54sd w 0.1 f 50 v c27 0.1 f 50 v c28 1 2 stage2 j8 1 2 stage3 j9 1 2 stage4 j10 0.22f 50v c29 0.22f 50v c30 avdd vi n 10pf 25v c26 wled+ wled- 1.2v 0.6v 0.6v 0.6v 0v figure 7: aat2823ibk evaluation board schematic. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 24 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 d1 100p f c8 200k ? r1 1 4. 7 f 10 vc 1 vi n n/ c 24 n/ c 1 n/ c 19 en 9 agnd 23 pgnd2 2 we n 5 fb p 10 n/ c 21 drvp 8 vd d 7 n/ c 20 op + 16 op in 15 pgnd 1 11 lx 12 comp 13 fb 14 op - 17 ou t 18 vi n 22 ref 3 fb n 4 drvn 6 u1 aat2824 10f 10 v c3 0.22f 6.3v c7 0.1 f 25 v c1 2 0. 22f 50 v c2 1 ad j r2 6.04k? r3 22 f 25 v c6 6.04k? r1 0 ad j r6 6.04k? r7 10k? r1 4 10k? r1 3 0? r1 0.1 f 50 v c1 3 0. 22f 25 v c1 8 0. 1 f 50 v c1 1 0. 1 f 25 v c1 0 0.22f 25 v c1 6 0. 22f 50 v c1 9 0.22f 50 v c1 7 j1 vi n en lx vavd d vgh (positive ) vgl (n egative) j2 vi n we n ad j r9 0.1 f 10 vc 2 2.2 h l1 0? r1 5 agnd vd d 3 4 5 6 2 1 a1 bat54sdw vd d open r1 6 3 4 5 6 2 1 a2 bat54sdw 0.1 f 50 v c1 4 0.1 f 50 v c1 5 3 4 5 6 2 1 a3 bat54sdw 0. 22f 50 v c2 0 1 2 stage 3 j5 1 2 stage 4 j6 0. 1 f c2 2 drv n drvp fb p fb n 0. 1 f 25 v c2 3 100? r1 7 10nf c2 4 1 2 stage 2 j4 vi n open r1 9 0? r1 8 vavd d 3 4 5 6 2 1 a4 bat54sdw 0. 1 f 50 v c2 7 0. 1 f 50 v c2 8 1 2 st age2 j8 1 2 st age3 j9 1 2 st age4 j10 0.22f 50 v c2 9 0.22f 50 v c3 0 avdd vi n vopi n 1 2 j7 10pf 25 v c2 6 1.2v 0.6v 0.6v 0v figure 8: aat2824ibk evaluation board schematic. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 25 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 d1 100p f c8 200k ? r1 1 4.7 f 10 vc 1 vi n n/c 24 n/c 1 n/ c 19 en 9 agnd 23 pgnd2 2 we n 5 fb p 10 n/ c 21 drvp 8 vdd 7 n/ c 20 n/c 16 n/c 15 pgnd1 11 lx 12 comp 13 fb 14 n/c 17 n/c 18 vin 22 re f 3 fb n 4 drvn 6 u1 aat282 5 10f 10 v c3 0.22f 6.3v c7 0.1 f 25 v c1 2 0.22 f 50 v c2 1 ad j r2 6.04k? r3 22 f 25 v c6 6.04k ? r1 0 ad j r6 6.04k? r7 0? r1 0.1 f 50 v c1 3 0.22 f 25 v c1 8 0.1 f 50 v c1 1 0.1 f 25 v c1 0 0.22f 25 v c1 6 0.22 f 50 v c1 9 0.22f 50 v c1 7 j1 vi n en lx vavdd vgh (posit iv e) vgl (negati ve ) j2 vin we n ad j r9 0.1 f 10 vc 2 2.2 h l1 agnd vd d 3 4 5 6 2 1 a1 bat54sd w vd d 3 4 5 6 2 1 a2 bat54sd w 0.1 f 50 v c1 4 0.1 f 50 v c1 5 3 4 5 6 2 1 a3 bat54sd w 0.22 f 50 v c2 0 1 2 stage 3 j5 1 2 stage4 j6 drvn drvp fb p fb n 0.1 f 25 v c2 3 1 2 stage 2 j4 vi n open r1 9 0? r1 8 vavdd 3 4 5 6 2 1 a4 bat54sdw 0.1 f 50 v c2 7 0.1 f 50 v c2 8 1 2 stage2 j8 1 2 stage3 j9 1 2 stage4 j1 0 0.22f 50 v c2 9 0.22f 50 v c3 0 avdd vi n 10pf 25 v c2 6 1.2v 0.6v 0.6v 0v figure 9: aat2825ibk evaluation board schematic. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 26 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 figure 10: aat28xxibk evaluation board figure 11: aat28xxibk evaluation board top side layout. bottom side layout. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 27 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 3. the leadless package family, which includes qfn, tqfn, dfn, tdfn and stdfn, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. a solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection. ordering information 1,2 package part marking 1 part number (tape and reel) 2 tqfn44-24 8xxyy aat2822ibk-t1 tqfn44-24 f8xyy aat2822ibk-1-t1 tqfn44-24 b7xyy aat2823ibk-t1 tqfn44-24 f9xyy aat2823ibk-1-t1 tqfn44-24 aat2824ibk-t1 tqfn44-24 aat2824ibk-1-t1 tqfn44-24 aat2825ibk-t1 tqfn44-24 aat2825ibk-1-t1 skyworks green? products are compliant with all applicable legislation and are halogen-free. for additional information, refer to skyworks de?nition of green? , document number sq04-0074. package information 3 tqfn44-24 4.000 0.050 2.700 0.050 pin 1 dot by marking 4.000 0.050 2.700 0.050 0.214 0.036 0.500 bsc 0.400 0.050 0.750 0.050 0.255 0.025 pin 1 identificationchafer 0.300 45 1 o ie botto ie side ie 0.000 ? 0.050 all dimensions in millimeters. downloaded from: http:///
aat2822/2823/2824/2825 da ta sheet tft-lcd dc/dc con ve rt er with wled driver and vcom buffer 28 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202081b ? skyworks proprietary information ? products and product information are subject to cha nge without notice. ? august 2, 2012 copyright ? 2012 skyworks solutions, inc. all rights reserved. information in this document is provided in connection with skyworks solutions, inc. (skyworks) pr oducts or services. these materials, including the information contained herein, are provided by sky works as a service to its customers and may be used for informational purposes only by the customer. skyworks a ssumes no responsibility for errors or omissions in these materials or the information contained her ein. sky- works may change its documentation, products, services, speciications or product descriptions at any time, without notice. skyworks makes no commitment to update the materials or information and shall have no responsibility whatsoever for conlicts, incompatibilities, or other dificulties arising from any fut ure changes. no license, whether express, implied, by estoppel or otherwise, is granted to any intellectual prope rty rights by this document. skyworks assumes no liability for any materials, products or informatio n provided here- under, including the sale, distribution, reproduction or use of skyworks products, information or ma terials, except as may be provided in skyworks terms and conditions of sale. the materials, products and information are provided as is without warranty of any kind, whether e xpress, implied, statutory, or otherwise, including fitness for a particular purpose or use, merchantability, performance, quality or non-infringement of any intellectual proper ty right; all such warranties are hereby expressly disclaimed. skyworks does not warrant the accuracy or completeness of the information, text, graphics or other items contained within these materials. skyworks shall not be liable for any damages, in- cluding but not limited to any special, indirect, incidental, statutory, or consequential damages, i ncluding without limitation, lost revenues or lost profits that may result from the use of the materials or information, whether or not the recipient of materials has been advised of the possibility of such damage. skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, o r other equipment in which the failure of the skyworks products could lead to personal injury, death , physical or en- vironmental damage. skyworks customers using or selling skyworks products for use in such applicatio ns do so at their own risk and agree to fully indemnify skyworks for any damages resulting from such improper use or sale. customers are responsible for their products and applications using skyworks products, which may dev iate from published speciications as a result of design defects, errors, or operation of products ou tside of pub- lished parameters or design speciications. customers should include design and operating safeguards to minimize these and other risks. skyworks assumes no liability for applications assistance, custom er product design, or damage to any equipment resulting from the use of skyworks products outside of stated pub lished speciications or parameters. skyworks, the skyworks symbol, and breakthrough simplicity are trademarks or registered trademarks of skyworks solutions, inc., in the united states and other countries. third-party brands and names are for identiication purposes only, and are the property of their respective owners. additional information , including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by refere nce. downloaded from: http:///

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