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four white led backlight driver adm8843 rev. c information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. specifications subject to change without notice. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781.329.4700 www.analog.com fax: 781.461.3113 ?2004C201 analog devices, inc. all rights reserved. features drives 4 leds from a 2.6 v to 5.5 v (li-ion) input supply 1/1.5/2 fractional charge pump to maximize power efficiency 0.3% typical led current matching up to 88% power efficiency over li-ion range powers main and sub display leds with individual shutdown package footprint only 9 mm 2 (3 mm 3 mm) package height only 0.55 mm low power shutdown mode shutdown function soft start limiting in-rush current applications cellular phones with main and sub displays white led backlighting camera flash/strobes and movie light applications micro tft color displays dsc pdas general description the adm8843 uses charge pump technology to provide the power to drive up to four leds. the leds are used for back- lighting a color lcd display that has regulated constant current for uniform brightness intensity. the main display can use up to three leds, and the sub display uses one led. the ctrl1 and ctrl2 digital input control pins control the shutdown opera- tion and the brightness of the main and sub displays. to maximize power efficiency, the charge pump can operate in 1, 1.5, or 2 mode. the charge pump automatically switches among 1/1.5/2 modes, based on the input voltage, to maintain sufficient drive for the led anodes at the highest power efficiency. improved brightness matching of the leds is achieved by a feedback pin that senses individual led current with a typical matching accuracy of 0.3%. functional block diagram current control 1 current control 2 current control 3 current control 4 control logic v ref charge pump 1 /1.5 /2 mode osc led current control circuit fb1 current controlled sinks fb2 fb3 fb4 v out c4 4.7 f v cc c1 1 f ctrl1 ctrl2 c2 1 f r set i set gnd c3 2.2 f adm8843 05050-001 main sub figure 1.
adm8843 rev. c | page 2 of 16 table of contents features .............................................................................................. 1 applications....................................................................................... 1 general description ......................................................................... 1 functional block diagram .............................................................. 1 revision history ............................................................................... 2 specifications..................................................................................... 3 absolute maximum ratings............................................................ 4 thermal characteristics .............................................................. 4 esd caution.................................................................................. 4 pin configuration and function descriptions............................. 5 typical performance characteristics ............................................. 6 theory of operation ........................................................................ 9 automatic gain control............................................................ 10 brightness control with a digital pwm signal ..................... 10 led brightness control using a pwm signal applied to v pwm .................................... 12 led brightness control using a dc voltage applied to v bright ................................... 12 applications..................................................................................... 13 layout considerations and noise ............................................ 13 white led shorting .................................................................. 13 driving four leds in the main display only ....................... 13 driving fewer than four leds ................................................ 13 using smaller capacitor values ............................................... 14 power efficiency......................................................................... 15 outline dimensions ....................................................................... 16 ordering guide .......................................................................... 16 revision history 1/11rev. b to rev. c changes to figure 14........................................................................ 7 4/10rev. a to rev. b removed cp-16-12 package .............................................universal change to figure 2 ........................................................................... 5 change to figure 6 ........................................................................... 6 changes to figure 14........................................................................ 7 changes to figure 15........................................................................ 8 updated outline dimensions ....................................................... 16 changes to ordering guide .......................................................... 16 12/06rev. 0 to rev. a change to thermal characteristics section ................................. 4 changes to outline dimensions................................................... 16 changes to ordering guide .......................................................... 16 10/04revision 0: initial version
adm8843 rev. c | page 3 of 16 specifications v cc = 2.6 v to 5.5 v; t a = ?40c to +85c, unless otherwise noted; c1, c2 = 1.0 f; c3 = 2.2 f; c4 = 4.7 f. table 1. parameter min typ max unit test conditions input voltage, v cc 2.6 5.5 v supply current, i cc 2.6 5 ma all four leds disabled, v cc = 3.3 v, r set = 7.08 k, ctrl1 = 1, crtl2 = 1 shutdown current 5 a charge pump frequency 1.5 mhz charge pump mode thresholds 1.5 to 2 3.33 v 2 to 1.5 3.36 v hysteresis 40 mv 1 to 1.5 4.77 v 1.5 to 1 4.81 v hysteresis 40 mv i set pin led : led matching 0.3 % i led = 20 ma, v fb = 0.4 v i set pin voltage 1.18 v i led -to-i set ratio 120 i led -to-i set ratio accuracy 5% min compliance on fbx pin 0.15 v i set = 15 ma charge pump output resistance 1.2 1 mode 3.5 1.5 mode 8.0 2 mode led current 20 ma pwm 1 0.1 200 khz digital inputs input high 0.7 v cc v input low 0.3 v cc v input leakage current 1 a charge pump power efficiency 88 % ctrl1 = 1, crtl2 = 1, v cc = 3.4 v, v fb = 0.2 v, i fb = 20 ma v out ripple 30 mv v cc = 3.6 v, i led = 20 ma, all four leds enabled 1 guaranteed by design. no t 100% production tested.
adm8843 rev. c | page 4 of 16 absolute maximum ratings t a = 25c, unless otherwise noted. table 2. parameter rating supply voltage, v cc C0.3 v to +6.0 v i set C0.3 v to +2.0 v ctrl1, ctrl2 C0.3 v to +6.0 v v out shorted 1 indefinite feedback pins fb1 to fb4 C0.3 v to +6.0 v operating temperature range C40c to +85c v out 2 180 ma storage temperature range C65c to +125c power dissipation 2 mw esd class 1 1 short through led. 2 based on long-term c urrent density limitations. stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. thermal characteristics 16-lead lfcsp (cp-16-3) package: ja =50c/w esd caution
adm8843 rev. c | page 5 of 16 pin configuration and fu nction descriptions pin 1 indicator 1v out 2 c2+ 3i set 4 gnd notes 1. connect the exposed paddle to gnd. 11 c2? 12 ctrl2 10 gnd 9gnd 5 f b 1 6 f b 2 7 f b 3 8 f b 4 1 5 v c c 1 6 c 1 + 1 4 c 1 ? 1 3 c t r l 1 top view (not to scale) adm8843 05050-003 figure 2. pin configuration table 3. pin function descriptions pin no. mnemonic description 1 v out charge pump output. a 2.2 f capacitor to ground is required on this pin. connect v out to the anodes of all the leds. 2 c2+ flying capacitor 2 positive connection. 3 i set bias current set input. the current flowing through the r set resistor, i set , is gained up by 120 to provide the i led current. connect a resistor, r set , to gnd to set the bias current as v set /r set . note that v set = 1.18 v. 4, 9, 10 gnd device ground pins. 5 to 8 fb1 to fb4 led1 to led4 cathode connection and charge pump feed back. the current flowing in these leds is 120 times the current flowing through r set , i set . when using fewer than four leds, this pin can be left unconnected or connected to gnd. 11 c2? flying capacitor 2 negative connection. 12 ctrl2 digital input. 3 v cmos logic. used with ctrl1 to control the shutdown operation of the main and sub leds. 13 ctrl1 digital input. 3 v cmos logic. used with ctrl2 to control the shutdown operation of the main and sub leds. 14 c1? flying capacitor 1 negative connection. 15 v cc positive supply voltage input. connect this pin to a 2.6 v to 5.5 v supply with a 4.7 f decoupling capacitor. 16 c1+ flying capacitor 1 positive connection. C ep expose paddle. connect the exposed paddle to gnd.
adm8843 rev. c | page 6 of 16 typical performance characteristics 5 10 15 20 25 30 35 10.75 05050-004 r set (k ) led current (ma) 4.75 6.75 12.75 14.75 8.75 figure 3. i led (ma) vs. r set 05050-005 temperature ( c) led current (ma) ?40 0 80 40 20.08 20.12 20.14 20.16 20.18 20.20 20.24 20.10 20.22 figure 4. i led (ma) variation over temperature (c), v cc = 3.6 v 0 4 8 12 16 20 05050-006 duty cycle (%) led current (ma) 0 20 60 100 80 40 figure 5. i led (ma) vs. pwm dimming (varying duty cycle), four leds enabled, frequency = 1 khz 20.00 20.10 20.15 20.20 20.25 20.30 20.35 4.1 05050-007 supply voltage (v) led current (ma) 2.6 3.1 4.6 5.6 3.6 5.1 ?40 c +25 c +85 c 20.05 figure 6. i led (ma) vs. temperature (c), four leds enabled 5 10 15 20 25 30 35 3.8 05050-008 supply voltage (v) led current (ma) 2.6 3.0 4.6 5.4 3.4 5.0 4.2 figure 7. i led (ma) vs. supply voltage (v) 60 65 70 80 90 95 05050-009 duty cycle (%) efficiency (%) 04 0 6 0 8 0 70 50 85 90 100 10 20 30 75 figure 8. led efficiency vs. varying duty cycle of 1 khz pwm signal, four leds enabled, 20 ma/led
adm8843 rev. c | page 7 of 16 60 80 100 120 160 180 05050-010 supply voltage (v) supply current (ma) 2.6 3.0 3.8 4.6 4.2 3.4 140 5.0 5.4 ?40 c +25 c +85 c figure 9. supply current vs. supply voltage over temperature, four leds enabled @ 20 ma/led 05050-011 ch2 20.0mv ch1 20.0mv m 10.0 s ch1 ?12.8mv 2 1 b w b w v out v cc figure 10. 1.5 mode operating waveforms 5050-012 ch2 20.0mv ch1 20.0mv m 400ns ch2 2.4mv 2 1 b w b w v out v cc figure 11. 1 mode operating waveforms 5050-013 ch2 160ma ch1 2.00v m 10.0 s ch2 ?2.44mv 2 1 b w b w c urrent 3 v out ctrl1/2 ch3 1.00v figure 12. soft start showing the initial in-rush current and v out variation, four leds @ 20 ma/led, v cc = 3.6 v 05050-014 ch2 20.0mv ch1 20.0mv m 400ns ch2 2.4mv 2 1 b w b w v out v cc figure 13. 2 mode operating waveforms 40 45 50 60 80 90 5050-015 v cc (v) power efficien c y (%) 70 55 65 75 85 v f = 4.0v v f = 3.8v v f = 4.3v v f = 3.2v v f = 3.6v 2.8 3.0 3.4 3.8 3.6 3.2 4.0 4.2 2.93.13.33.53.73.94.1 figure 14. power efficiency vs. supply voltage over li-ion range, four leds @ 20 ma/led
adm8843 rev. c | page 8 of 16 40 45 50 60 80 90 05050-016 v cc (v) power efficien c y (%) 70 55 65 75 85 v f = 4.0v v f = 3.8v v f = 4.3v v f = 3.2v v f = 3.6v 2.8 3.0 3.4 3.8 3.6 3.2 4.0 4.2 2.9 3.1 3.3 3.5 3.7 3.9 4.1 figure 15. power efficiency vs. supply voltage over li-ion range, four leds @ 15 ma/led 05050-017 ch2 2.00mv ch1 2.00v m 10.0ms ch2 4.36mv 2 1 v out ctrl1/2 : 44.0ms @: ?44.4ms c2 fall 200 s low signal amplitude figure 16. tpc delay
adm8843 rev. c | page 9 of 16 theory of operation the adm8843 charge pump driver for lcd white led back- lights implements a multiple-gain charge pump (1, 1.5, 2) to maintain the correct voltage on the anodes of the leds over a 2.6 v to 5.5 v (li-ion) input supply voltage. the charge pump automatically switches among 1/1.5/2 modes, based on the input voltage, to maintain sufficient drive for the led anodes, with v cc input voltages as low as 2.6 v. it also includes regulation of the charge pump output voltage for supply voltages up to 5.5 v. the adm8843s four leds are arranged into two groups, main and sub. the main display can have up to three leds (fb1 to fb3), and the sub display has one led (fb4) (see figure 18 ). the ctrl1 and ctrl2 digital in put control pins control the shutdown operation and the brightness of the main and sub displays (see table 4 ). table 4. shutdown truth table ctrl1 ctrl2 led shutdown operation 0 0 sub display off/main display off 0 1 sub display off/main display on 1 0 sub display on/main display off 1 1 sub display on/main display on an external resistor, r set , is connected between the i set pin and gnd. this resistor sets up a reference current, i set , which is internally gained up by 120 within the adm8843 to produce i led currents of up to 20 ma/led (i led = i set 120 and i set = 1.18 v/r set ). the adm8843 uses four separate current sinks to sense each led current individually with a typical matching performance of 0.3%. this current matching performance ensures uniform brightness across a color display. the adm8843 lets the user control the brightness of the white leds with a digital pwm signal applied to ctrl1 and/or ctrl2. the duty cycle of the applied pwm signal determines the brightness of the main and/or sub display backlight white leds. the adm8843 also allows the brightness of the white leds to be controlled using a dc voltage (see figure 17 ). soft start circuitry limits the in-rush current flow at power-up. the adm8843 is fabricated using cmos technology for minimal power consumption and is packaged in a 16-lead lead frame chip scale package. i set r set = 13.4k r = 15k v bright 0v?2.5v adm8843 05050-022 figure 17. pwm brightness control using a dc voltage applied to v bright current control 1 current control 2 current control 3 current control 4 control logic v ref charge pump 1 /1.5 /2 mode osc led current control circuit fb1 current controlled sinks fb2 fb3 fb4 v out c4 4.7 f v cc c1 1 f ctrl1 ctrl2 c2 1 f r set i set gnd c3 2.2 f adm8843 05050-001 main sub figure 18. functional block diagram
adm8843 rev. c | page 10 of 16 automatic gain control the automatic gain control block controls the operation of the charge pump by selecting the appropriate gain for the charge pump. doing so maintains sufficient drive for the led anodes at the highest power efficiency over a 2.6 v to 5.5 v input supply range. the charge pump switching thresholds are described in table 5 . table 5. charge pump switching thresholds gain threshold (v) 1.5 to 2 3.33 2 to 1.5 3.36 1 to 1.5 4.77 1.5 to 1 4.81 brightness control with a digital pwm signal pwm brightness control provides the widest brightness control method by pulsing the white leds on and off using one or both digital input control pins, ctrl1 and ctrl2. pwm brightness control also removes any chromaticity shifts associated with changing the white led current, because the leds operate at either zero current or full current (set by r set ). the digital pwm signal applied with a frequency of 100 hz to 200 khz turns the current control sinks on and off using ctrl1 and/or ctrl2. the average current through the leds changes with the pwm signal duty cycle. if the pwm frequency is much less than 100 hz, flicker may be seen in the leds. for the adm8843, zero duty cycle turns off the leds, and a 50% duty cycle results in an average led current, i led , that is half the pro- grammed led current. for example, if r set is set to program 20 ma/led, a 50% duty cycle results in an average i led of 10 ma/led, which is half the programmed led current. fb1 fb2 fb3 fb4 ctrl1 ctrl2 r set i set adm8845 05050-018 3.4v v cc v out i in c3 2.2 f c1 1 f c2 1 f pwm input or high/low pwm input or high/low figure 19. digital pwm brightne ss control application diagram applying a digital pwm signal to one or both digital input control pins, ctrl1 and ctrl2, adjusts the brightness of the sub and/or main displays. the adm8843s four white leds are organized into two groups, main display (fb1 to fb3) and sub display (fb4); refer to the theory of operation section. the brightness of the adm8843s main and sub displays can be controlled together or separately. this is achieved by applying a digital pwm signal to both the ctrl1 and ctrl2 pins. the duty cycle of the applied digital pwm signal determines the brightness of the main and sub displays together. varying the duty cycle of the applied pwm signal varies the brightness of the main and sub displays from 0% to 100%. by holding ctrl1 low and applying a digital pwm signal to ctrl2, the sub display is turned off and the main display is turned on. then the brightness of the main display is determined by the duty cycle of the applied digital pwm signal. by applying a digital pwm signal to ctrl1 and holding ctrl2 low, the sub display is turned on and the main display is turned off. then the brightness of the sub display is determined by the duty cycle of the applied digital pwm signal. by applying a digital pwm signal to ctrl1 and holding ctrl2 high, the sub display is turned on and the main display is turned on. then the brightness of the sub display is determined by the duty cycle of the applied digital pwm signal. the bright- ness of the main display is set to the maximum (maximum is set by r set ). by holding ctrl1 high and applying a digital pwm signal to ctrl2, the sub and main displays are turned on. then the brightness of the main display is determined by the duty cycle of the applied digital pwm signal. the brightness of the sub display is set to the maximum (maximum is set by r set ). when ctrl1 and ctrl2 are low, the led current control sinks shutdown. shutdown of the charge pump is delayed by 15 ms. this timeout period, t cp , allows the adm8843 to determine if a digital pwm signal is present on ctrl1 and ctrl2, or if the user has selected a full chip shutdown (see figure 20 ). if digital pwm brightness control of the leds is not required, a constant logic level 1 (v cc ) or logic level 0 (gnd) must be applied. the four white led in the adm8843 are arranged into two groups, sub and main. it is possible to configure the four leds as in table 6 . refer also to figure 20 .
adm8843 rev. c | page 11 of 16 table 6. digital inputs truth table ctrl1 ctrl2 led operation 0 0 sub display off/main display off (full shutdown) 1 , 2 0 1 sub display off/main display on 1 , 3 1 0 sub display on/main display off 1 , 2 1 1 sub display on/main display on (full on) 1 , 3 0 pwm sub display off/digital pwm brightness control on main display 4 , 5 pwm 0 digital pwm brightness control on sub display/main display off 2 , 4 1 pwm sub display on/digital pwm brightness control on main display 1 , 5 pwm 1 digital pwm brightness control on sub display/main display on 5 pwm pwm digital pwm brightness control on sub and main display 5 1 sub display on means the display is on with the maximum brightness set by the r set resistor. ctrl1 = 1 means a constant logic level (v cc ) is applied to ctrl1. 2 main display off means only the main display is off. ctrl2 = 0 means a constant logic level (gnd) is applied to ctrl2. 3 main display on means the display is on with the maximum brightness set by the r set resistor. ctrl2 = 1 means a constant logic level (v cc ) is applied to ctrl2. 4 sub display off means only the sub display leds is off. ctrl1 = 0 means a constant logic level (gnd) is applied to ctrl1. 5 pwm means a digital pwm signal is applied to the ctrl1 and/or the ctrl2 pin with a frequency from 100 hz to 200 khz. led config. full on sub and main 50% duty cycle main and sub off ctrl1 ctrl2 v out i led (sub) i led (main) sub display brightness main display brightness 37ms > t cp > 15ms shdn shdn 50% 50% 100% 100% 80% t cp 05050-020 main 80% duty cycle, sub off figure 20. application timing
adm8843 rev. c | page 12 of 16 led brightness control using a pwm signal applied to v pwm adding two external resistors and a capacitor, as shown in figure 21 , can also be used for pwm brightness control. this pwm brightness control method can be used instead of ctrl1 and/or ctrl2 digital pwm brightness control. with this con- figuration, ctrl1 and ctrl2 digital logic pins can control shutdown of the white leds, and v pwm can control the bright- ness of all the white leds. this is done by applying a high frequency pwm signal (amplitude 0 v to 2.5 v) to drive an r-c-r filter on the i set pin of the adm8843. a 0% pwm duty cycle corresponds to 20 ma/led, and a 100% pwm duty cycle corresponds to a 0 ma/led. at pwm frequencies above 5 khz, c5 may be reduced (see figure 21 ). the amplitude of the pwm signal must only be 0 v and 2.5 v to result in 20 ma flowing in each led. 100 ) 1( 120 2 2 _ cycleduty rr rr voltage i i set set set led ? + = i set r set = 13.4k r = 7.5k v pwm 0v?2.5v adm8843 05050-021 100% = i led = 0ma 0% = i led = 20ma r = 7.5k c5 = 1 f figure 21. pwm brightness control using filter-pwm signal led brightness control using a dc voltage applied to v bright by adding one resistor, as shown in figure 17 , this configuration can also be used for brightness control of the white leds by using a dc voltage applied to the v bright node. figure 22 shows an application example of led brightness control using a dc voltage with an amplitude of 0 v to 2.5 v applied to v bright . the equation for i led is i set = [(1/ r set + 1/ r )( v set )] C [(1/ r )( v bright )] i led = 120 i set where: r = 15 k v set = voltage at i set pin (1.18 v) v bright 05050-023 i led 2.5v 0ma 1.6v 7.2ma 0.8v 13.6ma 0v 20ma figure 22. pwm brightness contro l application diagram using a dc voltage applied to v bright
adm8843 rev. c | page 13 of 16 applications layout considerations and noise because of the adm8843s switching behavior, pcb trace layout is an important consideration. to ensure optimum performance, a ground plane should be used, and all capacitors (c1, c2, c3, c4) must be located with minimal track lengths to the pins of the adm8843. white led shorting if an led is shorted, the adm8843 continues to drive the remaining leds with i led per led (i led = i set 120 ma). this is because the adm8843 uses four internal current sinks to produce the led current. if an led is shorted, the adm8843 continues to sink (i set 120 ma). driving four leds in the main display only the adm8843 can be operated with four leds in the main display only (see figure 23 ). with this configuration, ctrl1 and ctrl2 are used together to control the main display shutdown operation and brightness control. driving fewer than four leds the adm8843 can be operated with fewer than four leds in parallel by simply leaving the unused fbx pins floating or by connecting them to gnd. for example, figure 24 shows three leds being powered by the adm8843. v out fb1 fb2 fb3 fb4 v cc 2.6v?5.5v ctrl1 ctrl2 gnd adm8843 05050-024 lcd r set i set figure 23. driving four white leds v out fb1 fb2 fb3 fb4 v cc 2.6v?5.5v ctrl1 ctrl2 gnd adm8843 05050-025 main display r set i set figure 24. driving three white leds v out fb1 fb2 fb3 fb4 v cc 2.6v?5.5v ctrl1 ctrl2 gnd adm8843 r set i set 05050-002 main display sub display figure 25. typical application diagram
adm8843 rev. c | page 14 of 16 using smaller capacitor values the adm8843 can be operated with the smaller capacitor values described here to reduce capacitor footprint sizes. option 1 input and output ripple plots for 1 and 1.5 modes of operation are shown with c1, c2 = 0.22 f; c3 = 0.47 f; and c4 = 1 f. 05050-026 ch2 10.0mv ch3 10.0mv m 400ns ch3 ?33mv 3 2 b w b w v out v cc figure 26. 1 mode operation, four leds with 20 ma/led at v cc = 5.0 v, with a 1 f v cc decoupling capacitor 05050-027 ch2 20.0mv m 400ns ch3 ?33mv 3 2 b w v out v cc ch3 50.0mv b w figure 27. 1.5 mode operation, four leds with 20 ma/led at v cc = 3.6 v, with a 1 f v cc decoupling capacitor option 2 input and output ripple plots for 1 and 1.5 modes of operation are shown with c1, c2 = 0.22 f; c3 = 0.47 f; and c4 = 4.7 f. 05050-028 ch2 10.0mv ch3 10.0mv m 1.00 s ch3 ?33mv 3 2 b w b w v out v cc figure 28. 1 mode operation, four leds with 20 ma/led at v cc = 5.0 v, with a 4.7 f v cc decoupling capacitor 05050-029 ch2 20.0mv ch3 50.0mv m 400ns ch3 ?33mv 3 2 b w b w v out v cc figure 29. 1.5 mode operation, four leds with 20 ma/led at v cc = 3.6 v, with a 4.7 f v cc decoupling capacitor
adm8843 rev. c | page 15 of 16 power efficiency the adm8843 power efficiency () equations are as follows: = p out / p in p in = (( v cc i load gain ) + ( i q v cc )) p out = 4 ( v f i led ) where: i q is the quiescent current of the adm8843, 2.6 ma. v f is the led forward voltage. gain is the charge pump mode (1, 1.5, 2). example 1 the adm8843 driving four white led with 20 ma/led at v cc = 3.4 v (1.5 mode), led v f = 4.5 v. p in = (( v cc i load gain ) + ( v cc i q )) p in = ((3.4 80 ma 1.5) + (3.4 2.6 ma)) p in = ((0.408) + (0.00884)) p in = 0.41684 p out = 4( v f i led ) p out = 4(4.5 v 20 ma) p out = 0.36 = p out / p in = 0.36/0.41684 = 87 % v out fb1 fb2 fb3 fb4 v cc = 3.4v ctrl1 ctrl2 gnd adm8843 r set 7.32k i set 05050-019 v cc i in i load figure 30. charge pump power efficiency diagram, example 1 example 2 the adm8843 driving four white led with 20 ma/led at v cc = 3.4 (1.5 mode), led v f = 3.6 v. p in = (( v cc i load gain ) + ( v cc i q )) p in = ((3.4 80 ma 1.5) + (3.4 2.6 ma)) p in = ((0.408) + (0.00884)) p in = 0.41684 p out = 4( v f i led ) p out = 4(3.6 v 20 ma) p out = 0.288 = p out / p in = 0.288/0.41684 = 70 %
adm8843 rev. c | page 16 of 16 outline dimensions * compliant to jedec standards mo-220-veed-2 except for exposed pad dimension. 1 0.50 bsc 0.60 max p i n 1 i n d i c a t o r 1.50 ref 0.50 0.40 0.30 0.25 min 0.45 2.75 bsc sq top view 12 max 0.80 max 0.65 typ seating plane pin 1 indicator 0.90 0.85 0.80 0.30 0.23 0.18 0.05 max 0.02 nom 0.20 ref 3.00 bsc sq * 1.65 1.50 sq 1.35 16 5 13 8 9 12 4 exposed pad bottom view for proper connection of the exposed pad, refer to the pin configuration and function descriptions section of this data sheet. 07-17-2008-a figure 31. 16-lead lead frame chip scale package [lfcsp_vq] 3 mm 3 mm body, very thin quad (cp-16-3) dimensions shown in millimeters ordering guide model 1 temperature range package description package option branding adm8843acpz-reel7 ?40c to +85c 16-lead lead frame chip scale package [lfcsp_vq] cp-16-3 m2u adm8843eb-evalz evaluation board 1 z = rohs compliant part. ?2004C2011 analog devices, inc. all rights reserved. trademarks and registered trademarks are the prop erty of their respective owners. d05050-0-1/11(c)

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