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dual led flash driver with i 2 c-compatible interface ADP1655 rev. 0 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 ?2009 analog devices, inc. all rights reserved. features ultracompact solution small 2 mm 1.5 mm 12-ball wlcsp package tiny, low profile 2.2 h power inductor led current source for loca l led grounding and low emi synchronous 2 mhz pwm boost convertor, no external diode high efficiency: 88% peak reduces high levels of input battery current during flash limits battery current drain in torch mode i 2 c programmable currents up to 400 ma in flash mode for two leds currents up to 500 ma in flash mode for one led with 5% accuracy currents up to 160 ma in torch mode with 10% accuracy peak inductor current limit flash timer control i 2 c-compatible control registers external strobe pin external direct torch pin tx_mask input to prevent high input battery current levels safety thermal overload protection flash timeout inductor fault detection output overvoltage short circuit protection soft start reduces inrush input current applications camera-enabled cellular phones and smart phones digital still cameras, camcorders, and pdas functional block diagram ADP1655 10f 2.2h input voltage = 2.5v to 5.5v torch scl/en1 i2c/en sgnd pgnd sda/en2 vout led_out tx_mask strobe vin sw 0 8028-001 10f figure 1. l1 inductor digital input/ output led anode li-ion + li-ion + pgnd c1 3mm 6.5mm c2 08028-002 figure 2. pcb layout general description the ADP1655 is a very compact, highly efficient, dual white led flash driver for high resolution camera phones, which improves picture and video quality in low light environments. the device integrates a 2 mhz synchronous inductive boost convertor, an i 2 c-compatible interface and a 500 ma current source. the high switching frequency enables the use of a tiny, low profile 2.2 h power inductor, and the current source permits led cathode grounding for thermally enhanced, low emi and compact layouts. the efficiency is high over the entire battery voltage range to maximize the input power to led power conversion and minimize battery current draw during flash events. in addition, a tx-mask input permits the flash led current to reduce quickly and, therefore, the battery current reduces quickly, during a gsm power amplifier current burst. the i 2 c-compatible interface enables the programmability of timers, currents, and status bit readback for operation monitoring and safety control. the ADP1655 comes in a compact 12-ball 0.5 mm pitch wlcsp package and is specified over the full ?40c to +125c junction temperature range.
ADP1655 rev. 0 | page 2 of 24 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 functional block diagram .............................................................. 1 general description ......................................................................... 1 revision history ............................................................................... 2 specifications ..................................................................................... 3 recommended specifications: input and output capacitance and inductance ............................................................................. 4 i 2 c-compatible interface timing specifications ..................... 5 absolute maximum ratings ............................................................ 6 thermal data ................................................................................ 6 thermal resistance ...................................................................... 6 esd caution .................................................................................. 6 pin configuration and function descriptions ............................. 7 typical performance characteristics ............................................. 8 theory of operation ...................................................................... 12 white led driver ...................................................................... 12 assist light and torch modes .................................................. 12 2-bit logic interface mode (i2c/en = 0) ............................... 13 i 2 c interface mode (i2c/en = 1) ............................................. 13 state transitions ......................................................................... 15 i 2 c register map ............................................................................. 16 safety features ................................................................................. 19 overvoltage fault ....................................................................... 19 output capacitor fault .............................................................. 19 timeout fault .............................................................................. 19 overtemperature fault .............................................................. 19 short-circuit fault ..................................................................... 19 current limit .............................................................................. 19 amount of led detection ........................................................ 19 input undervoltage .................................................................... 19 applications information .............................................................. 20 external component selection ................................................ 20 pcb layout ...................................................................................... 22 outline dimensions ....................................................................... 23 ordering guide .......................................................................... 23 revision history 5/09revison 0: initial version
ADP1655 rev. 0 | page 3 of 24 specifications v in = 3.6 v, t j = ?40c to +125c for minimum/maximum specifications and t a = 25c for typical specifications, unless otherwise noted. table 1. parameter 1 conditions min typ max unit supply input voltage range 2.7 5.5 v undervoltage lockout threshold v in falling 2.3 2.4 2.5 v hysteresis 50 100 150 mv shutdown current t j = ?40c to +85c, current into vin pin, v in = 2.7 v to 4.5 v 0.3 1 a standby current t j = ?40c to +85c, current into vin pin, v in = 2.7 v to 4.5 v 3 10 a i2c/en = scl/en1 = sda/en2 = 1.8 v operating quiescent current torch mode, two leds, led current = 40 ma 5.3 ma sw switch leakage t j = ?40c to +85c 1 a inputs input logic low voltage 0.54 v input logic high voltage 1.26 v torch, strobe, tx_mask pull-down 350 k scl/en1, sda/en2 pull-down i2c/en = 0 v 350 k torch glitch filtering delay from torch rising edge to device start 6.3 9 11.7 ms led driver led current assist light, torch i2c/en = 0, one led 80 ma i2c/en = 0, two leds 40 ma i2c/en = 1, assist light value setting = 0 (000 binary) 20 ma i2c/en = 1, assist light value setting = 7 (111 binary) 160 ma flash i2c/en = 0, one led 500 ma i2c/en = 0, two leds 320 ma i2c/en = 1, flash value setting = 0 (0000 binary) 200 ma i2c/en = 1, one led, flash value setting = 15 (1111 binary) 500 ma i2c/en = 1, two leds, flash value setting = 10 to 15 (1010 to 1111 binary) 400 ma led current accuracy i led = 320 ma to 500 ma ?5 +5 % i led = 60 ma to 320 ma ?5 +10 % i led = 20 ma to 60 ma ?5 +20 % led current source headroom 2 flash typical, 400 ma led current 290 mv torch 160 ma 190 led_out ramp-up time 1 ms led_out ramp-down time 0.5 ms maximum timeout for flash 850 ms timer accuracy ?7.5 +7.5 % switching regulator switching frequency 1.85 2 2.15 mhz minimum duty cycle 9.0 % n-fet resistance 135 m p-fet resistance 290 m
ADP1655 rev. 0 | page 4 of 24 parameter 1 conditions min typ max unit safety features thermal shutdown threshold t j rising 150 c t j falling 140 c overvoltage threshold 9.0 9.5 10.1 v coil peak current limit peak current value setting = 0 (00 binary) 1.13 1.25 1.38 a peak current value setting = 1 (01 binary) 1.35 1.5 1.65 a peak current value setting = 2 (10 binary) 1.58 1.75 1.93 a peak current value setting = 3 (11 binary) 1.8 2.0 2.2 a led_out short-circuit detection comparator reference voltage 1.2 1.3 v led counting comparator threshold voltage led value setting = 0 (00 binary) 4.3 v led value setting = 1 (01 binary) 4.6 v led value setting = 2 (10 binary) 4.0 v led value setting = 3 (11 binary) 4.9 v 1 all limits at temperature extremes ar e guaranteed via correlation using standard statistical quality control (sqc). 2 two leds are used for this parameter. recommended specifications: input and output capacitance and inductance table 2. parameter symbol conditions min typ max unit capacitance c min input t a = ?40c to +125c 4.0 f output t a = ?40c to +125c 4.0 20 f minimum and maximum inductance l t a = ?40c to +125c 1.5 2.8 h
ADP1655 rev. 0 | page 5 of 24 i 2 c-compatible interface timing specifications table 3. parameter 1 min max unit description f scl 400 khz scl clock frequency t high 0.6 s scl high time t low 1.3 s scl low time t su, dat 100 ns data setup time t hd, dat 0 0.9 s data hold time t su, sta 0.6 s setup time for repeated start t hd, sta 0.6 s hold time for start/repeated start t buf 1.3 s bus free time between a stop and a start condition t su, sto 0.6 s setup time for stop condition t r 20 + 0.1 c b 2 300 ns rise time of scl and sda t f 20 + 0.1 c b 300 ns fall time of scl and sda t sp 0 50 ns pulse width of suppressed spike c b 400 pf capacitive load for each bus line 1 guaranteed by design. 2 c b is the total capacitance of one bus line in picofarads. sd a scl s s = start condition sr = repeated start condition p = stop condition sr p s t low t r t hd, dat t high t su, dat t f t f t su, sta t hd, sta t sp t su, sto t buf t r 08028-003 figure 3. i 2 c-compatible interf ace timing diagram
ADP1655 rev. 0 | page 6 of 24 absolute maximum ratings table 4. parameter rating vin, sda/en2, scl/en1, i2c/en, strobe, torch, tx_mask to sgnd ?0.3 v to +6 v led_out, sw, vout to sgnd ?0.3 v to +12 v pgnd to sgnd ?0.3 v to +0.3 v vout to led_out ?0.3 v to +6 v ambient temperature range (t a ) ?40c to +85c junction temperature range (t j ) ?40c to +125c storage temperature jedec j-std-020 esd human body model 2000 v esd charged device model 1000 v esd machine model 200 v 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 data the ADP1655 may be damaged if the junction temperature limits are exceeded. monitoring t a does not guarantee that t j is within the specified temperature limits. in applications with high power dissipation and poor thermal resistance, the maximum t a may have to be derated. in applications with moderate power dissipation and low pcb thermal resistance, the maximum t a can exceed the maximum limit as long as the t j is within speci- fication limits. t j of the device is dependent on the t a , the power dissipation (pd) of the device, and the junction-to-ambient thermal resistance ( ja ) of the package. maximum t j is calculated from the t a and pd using the following formula: t j = t a + ( pd ja ) thermal resistance ja of the package is based on modeling and calculation using a 4-layer board. ja is highly dependent on the application and board layout. in applications where high maximum power dissi- pation exists, attention to thermal board design is required. the value of ja may vary, depending on pcb material, layout, and environmental conditions. the specified value of ja is based on a 4-layer, 4 in 3 in, 2 1/2 oz copper board, per jedec standards. for more information, see the an-617 application note, microcsp tm wafer level chip scale package. ja is specified for a device mounted on a jedec 2s2p pcb. table 3. thermal resistance package type ja unit 12-ball wlcsp 75 c/w esd caution
ADP1655 rev. 0 | page 7 of 24 pin configuration and fu nction descriptions top view (ball side down) not to scale pgnd sgnd vin sw torch tx_mask vout strobe i2c/en led_out sda/en2 scl/en1 1 a b c d 23 ball a 1 indicator 08028-004 figure 4. pin configuration table 5. pin function descriptions pin no. mnemonic type description a1 pgnd ground ground for internal switching fet. a2 sgnd ground connect this pin at a single point to the power ground. a3 vin supply connect the battery between vin and pgnd. bypass vin with a 10 f, 6.3 v or greater x5r/x7r capacitor. b1 sw output connect a 2.2 h inductor between sw and the battery. b2 torch digital input this pin enables the torch, provided that the device is not in flash or assist light mode. b3 tx_mask digital input connect a digital signal to the tx_mask pin. when the logic level is driven high during a flash event the current is reduced to the torch level. c1 vout output vout senses the output voltage of the boost converter and provides the input voltage to the led current source. the vout pin features a comparator to detect an overvoltage condition if the led string is open circuited. connect a 10.0 f capacitor between vout and pgnd. c2 strobe digital input/ output the strobe input is used to synchronize the timin g of the camera module to the led driver in i 2 c-compatible interface mode. in 2-bit logic interfac e mode, this acts as an output, indicating the number of leds attached. strobe = high indicates two leds, whereas strobe = low indicates one led. c3 i2c/en digital input a logic low selects the 2-bit logic interface, whereas logic high selects i 2 c-compatible interface. if i2c/en is low and sda/en2 and scl/en1 are lo w, the driver enters shutdown mode with consumption < 1 a. d1 led_out output white led anode connection. connect led_out to the anode of the white led. led_out is internally connected to a programmable pmos current source, which regulates the led current. d2 sda/en2 digital input/ output data input/output (sda). in 2-bit logic interface mode, sda/en2 is the second input bit of the digital interface. second input bit (en2). in i 2 c mode, sda is the data input/output of the i 2 c-compatible interface. d3 scl/en1 digital input clock input (scl). in 2-bit logic interface mode, scl/en 1 is the first input bit of the digital interface. first input bit (en1). in i 2 c mode, scl is the clock input of the i 2 c-compatible interface.
ADP1655 rev. 0 | page 8 of 24 typical performance characteristics i led (ma) 600 500 400 300 200 100 0 input voltage (v) 4.2 4.7 5.2 3.7 3.2 2.7 08028-005 i limit ? 2.00a i limit ? 1.75a i limit ? 1.50a i limit ? 1.25a figure 5. maximum current vs. input voltage, one led i led (ma) 450 400 350 300 250 200 150 100 50 0 input voltage (v) 4.2 4.7 5.2 3.7 3.2 2.7 i limit ? 2.00a i limit ? 1.75a i limit ? 1.50a i limit ? 1.25a 08028-006 figure 6. maximum current vs. input voltage, two leds; led forward voltage (vf) = 4.3 v for each led channel 1 (i l ) 0.5a/div channel 2 (i hpled ) 0.2a/div channel 3 (v out ) 5v/div channel 4 (strobe) 5v/div l = fdse0312-2r2m c out =10f : 335 s 50s/div 4 3 2 1 08028-007 figure 7. startup, two leds flash mode, i led = 400 ma, v in = 3.2 v channel 1 (i l ) 0.5a/div channel 2 (i hpled ) 0.2a/div channel 3 (v out ) 5v/div channel 4 (strobe) 5v/div l = fdse0312-2r2m c out =10f : 335 s 50s/div 4 3 2 1 08028-008 figure 8. startup, two leds flash mode, i led = 400 ma, v in = 3.6 v channel 1 (i l ) 0.5a/div channel 2 (i hpled ) 0.2a/div channel 3 (v out ) 5v/div channel 4 (scl) 5v/div l = fdse0312-2r2m c out =10f : 180s 50s/div 4 3 2 1 08028-009 figure 9. startup, two leds assist light mode, i led = 40 ma, v in = 3.2 v channel 1 (i l ) 0.5a/div channel 2 (i hpled ) 0.2a/div channel 3 (v out ) 5v/div channel 4 (scl) 5v/div l = fdse0312-2r2m c out =10f : 180s 50s/div 4 3 2 1 08028-010 figure 10. startup, two leds torch mode, i led = 40 ma, v in = 3.6 v
ADP1655 rev. 0 | page 9 of 24 channel 1 (i l ) 0.2a/div channel 2 (i hpled ) 0.1a/div channel 3 (led_out) 5v/div channel 4 (sw) 5v/div l = fdse0312-2r2m c out =10f 500ns/div 4 2 3 1 08028-011 figu .6 v re 11. inductor current, two leds flash mode, i led = 400 ma, v in = 3 channel 1 (i l ) 0.2a/div channel 2 (i hpled ) 0.02a/div channel 3 (led_out) 5v/div channel 4 (sw) 5v/div l = fdse0312-2r2m c out =10f 500ns/div 4 3 2 1 08028-012 figure 12. inductor current, two leds torch mode, i led = 40 ma, v in = 3.6 v ?10 ?8 ?6 ?4 ?2 0 2 4 6 8 10 output current (ma) i led accuracy (%) 04 300 200 100 500 08028-013 0 0 v in = 3.2v v in = 3.6v v in = 4.2v figure 13. led current accuracy vs. output current output current (a) 0 10 20 30 40 50 60 70 80 90 100 efficien c y (%) 10 100 1000 08028-014 v in = 3.2v v in = 3.6v v in = 4.2v figure series 14. efficiency p led /p in , two high power white leds in 0 10 20 30 40 50 60 70 80 90 100 efficiency (%) 10 100 1k output current (a) v in = 3.2v v in = 3.6v v in = 4.2v 08028-015 figure 15. efficiency p led /p in , one high power white led channel 1 (ibat) 1a/div channel 2 (i hpled ) 0.2a/div channel 3 (v out ) 5v/div channel 4 (tx_mask) 5v/div l = fdse0312-2r2m c out =10f :4s 20s/div 4 3 2 1 08028-016 figure 16. tx masking response, tx_mask = 0 v to 1.8 v, i led = 40 ma to 400 ma, v in = 3.2 v
ADP1655 rev. 0 | page 10 of 24 channel 1 (ibat) 1a/div channel 2 (i hpled ) 0.2a/div channel 3 (v out ) 5v/div channel 4 (tx_mask) 5v/div l = fdse0312-2r2m c out =10f : 260s 100s/div 4 3 2 1 08028-017 figure 17. tx masking response, tx_mask = 1.8 v to 0 v, i led = 40 ma to 400 ma, v in = 3.2 v channel 1 (i hpled ) 0.1a/div channel 2 (strobe) 1v/div channel 3 (scl) 5v/div 200ms/div 3 2 1 0 8028-018 figure 18. assist light and flash, st robe edge sensitive mode, two leds, timer = 850 ms, i led = 40 ma to 400 ma, v in = 3.6 v channel 1 (i hpled ) 0.1a/div channel 2 (strobe) 1v/div channel 3 (scl) 5v/div 200ms/div 3 2 1 0 8028-019 figure 19. assist light and flash, st robe level sensitive mode, two leds, i led = 40 ma to 400 ma, v in = 3.6 v channel 1 (v in ) 0.5v/div channel 2 (i hpled ) 20ma/div l = fdse0312-2r2m c out =10f 100s/div 1 : 15m a 08028-020 figure 20. line transient, v in = 3.2 v to 3.6 v, i led = 400 ma 1.2 1.4 1.6 1.8 2.0 2.2 2.4 ?40 ?20 0 20 40 60 80 temperature (c) peak current limit (a) 08028-021 v in = 3.2v v in = 3.6v v in = 4.2v figure 21. coil peak current limit vs. temperature, output mode register = 00, 01, 10, and 11 (binary) 0 0.2 0.4 0.6 0.8 1.0 1.2 temperature (c) ?40 ?20 0 20 40 60 80 shutdown current (a) 08028-022 v in = 2.5v v in = 3.6v v in = 4.5v figure 22. shutdown current vs. temperature vs. v in
ADP1655 rev. 0 | page 11 of 24 ?40?200 20406080100120 temperature (c) 36 38 40 42 44 i led (ma) v in = 3.0v v in = 3.6v v in = 5.5v 08028-026 figure 26. led regulation, set at 40 ma, current set register = 001 (binary) temperature (c) 380 385 390 395 400 405 410 415 420 i led (ma) ?40 ?20 0 20 40 60 80 100 120 08028-027 v in = 3.0v v in = 3.6v v in = 5.5v figure 27. led regulation, set at 400 ma, current set register = 1010 (binary) temperature (c) 4.0 4.5 5.0 5.5 6.0 6.5 7.0 ?40?200 20406080 i vin (ma) 08028-023 v in = 3.2v v in = 3.6v v in = 4.2v figure 23. operating quiescent current vs. temperature, torch mode temperature (c) ?40 ?20 0 20 40 60 80 100 120 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 v in = 2.5v v in = 3.6v v in = 4.5v standby current ( a) 08028-024 figure 24. standby current vs. temperature vs. v in , i2c/en = scl/en1 = sda/en2 = 1.8 v ?40?200 20406080100120 temperature (c) 1.85 1.90 1.95 2.00 2.05 2.10 2.15 switching frequency (mhz) v in = 3.2v v in = 3.6v v in = 4.2v 08028-025 figure 25. switching frequency vs. temperature vs. v in
ADP1655 rev. 0 | page 12 of 24 theory of operation the ADP1655 is a high power, white led driver ideal for driving white leds for use as a camera flash. the ADP1655 includes a boost converter and a current regulator suitable for powering one or two high power, white leds. the ADP1655 responds to a 2-pin control interface that can operate in two separate pin-selectable modes: tying the i2c/ en pin high enables the i 2 c interface; tying the i2c/en pin low enables a 2-bit logic interface. white led driver the ADP1655 drives a synchronous boost converter to power one or two series-connected, high power leds. the white led driver regulates the high power led current for accurate brightness control. the ADP1655 uses an integrated pfet current regulator. when the white led is turned on, the step-up converter output voltage slew is limited to prevent excessive battery current while charging the output capacitor. the output voltage of the boost converter is sensed at vout. if the output voltage exceeds the 9.5 v (typical) limit, the white led driver turns off and indicates that a fault condition has occurred through the system registers. this feature prevents damage due to an overvoltage if the white led string fails with an open-circuit condition. setting the led regulation currents depends on the 2-pin control interface used. assist light and torch modes the ADP1655 features a programmable assist light mode that provides continuous led current. the strobe pin or the 2-bit logic interface can be used to transition from assist light mode directly to flash mode. the torch pin provides an alternative means of accessing a continuous led current mode of opera- tion. both assist light and torch modes deliver the same current, which is programmable via the i 2 c-compatible interface. pwm controller pgnd pgnd vout sw pgnd sgnd vin uvlo 2.5 v ovp fault register hpled short thermal protection hpled driver current sense current sense scl/en1 sda/en2 torch strobe tx_mask pgnd pgnd agnd c out l1 input voltage = 2.5v to 5.5v c in c3 a3 b1 c1 a1 a2 d1 d2 d3 c2 b3 b2 i2c/en interface and control 9.5v 4.35v cout detector high power led current control led_out 08028-029 figure 28. detailed block diagram
ADP1655 rev. 0 | page 13 of 24 2-bit logic interface mode (i2c/en = 0) in 2-bit logic interface mode, the two control pins, en1 and en2, select whether the part is disabled or operating in assist light mode or flash mode, as outlined in table 6 . additionally, the torch pin selects torch mode. figure 29 illustrates state transitions of 2-bit logic mode con- trolled by digital inputs en1, en2, torch, and tx_mask. external torch flash shutdown assist light en2 = 1 08028-030 en2 = 0 en1 = 0 en1 = 1 en1 = 1 en2 = 1 en1 = 0 en2 = 1 timeout en1 = 1 en2 = 1 en1 = 0 en2 = 0 torch = 0 torch = 1 figure 29. 2-bit logic mode state transitions (i2c/en = 0) when the ADP1655 is in flash mode, the tx_mask pin can be used to reduce the battery load. the device remains in flash mode, but the led driver output current is reduced to the assist light level. table 6. 2-bit logic interface mode selection mode i2c/ en en1 en2 torch output current shutdown 0 0 0 0 0 ma torch 0 0 0 1 one led: 80 ma two leds: 40 ma assist light 0 0 1 x one led: 80 ma two leds: 40 ma reserved 0 1 0 x 0 ma flash 0 1 1 x one led: 500 ma two leds: 320 ma i 2 c interface mode (i2c/en = 1) the ADP1655 includes an i 2 c-compatible serial interface for control of the led current, as well as for a readback of system status registers. the i 2 c chip address is 0x60 in write mode and 0x61 in read mode. table 7. i 2 c interface mode selection mode i2c/ en scl sda torch output current standby 1 x x 0 0 ma torch 1 x x 1 20 ma to 160 ma 1, 2 assist light 1 x x x 20 ma to 160 ma 2 flash 1 x x x 200 ma to 500 ma 2 1 torch mode has to be enabled from register 0x04. 2 the output current value depe nds on the register settings. registers values are reset to the default values when vin supply falls below the undervoltage (uvlo) level. figure 30 illustrates the i 2 c write sequence to a single register. the subaddress content selects which of the five ADP1655 registers is written to first. the ADP1655 sends an acknowl- edgement to the master after the 8-bit data byte has been written. the ADP1655 increments the subaddress automatically and starts receiving a data byte to the following register until the master sends an i 2 c stop as shown in figure 31 . figure 32 shows the i 2 c read sequence of a single register. ADP1655 sends the data from the register denoted by the subaddress and increments the subaddress automatically, sending data from the next reg- ister until the master sends an i 2 c stop condition as shown in figure 33 . state transitions between standby, assist light, flash, and external torch modes are described in the state transitions section and figure 34 . the register definitions are shown in the i 2 c register map section. the lowest bit number (0) represents the least significant bit, and the highest bit number (7) represents the most significant bit.
ADP1655 rev. 0 | page 14 of 24 subaddress chip address 01 100 00 0 00 0 = write 0 a dp1655 ack ADP1655 ack ADP1655 ack ADP1655 receives data s t s p master stop 08028-032 figure 30. i 2 c single register write sequence ADP1655 ack ADP1655 ack ADP1655 ack ADP1655 ack ADP1655 ack chip address s t 0110000 0 00 s p 0 = write 0 0 master stop 0 ADP1655 receives data to last register subaddress register n ADP1655 receives data to register n + 1 ADP1655 receives data to register n 08028-033 figure 31. i 2 c multiple register write sequence ADP1655 ack ADP1655 ack ADP1655 ack chip address 011000 0 0 0 1 0 master stop chip address s t s t 0110000 0 1 0 0 = write 1 = read s p master ack ADP1655 sends data subaddress 08028-034 figure 32. i 2 c single register read sequence a dp1655 ack a dp1655 ack a dp1655 ack s t s t chip address chip address 011000 0 0 0 0 0 0 master stop 1 0110000 0 1 0 0 = write 1 = read s p master ack master ack master ack ADP1655 sends data of last register ADP1655 sends data of register n + 1 ADP1655 sends data of register n subaddress register n 0 8028-035 figure 33. i 2 c multiple register read sequence
ADP1655 rev. 0 | page 15 of 24 state transitions when the ADP1655 is in flash mode, the tx_mask pin can be used to reduce the battery load. the device remains in flash mode, but the led driver output current is reduced to the assist light level. in figure 34 , if the flash was triggered by the strobe pin in level-sensitive mode, a timeout triggers a timeout fault, as defined in the safety features section. external torch flash standby i2c/en = 1 assist light output off timeout output on strobe = 1 output on strobe disabled mode = flash mode = assist light strobe = 1 tx_mask = 0 strobe disabled mode = flash tx_mask = 0 output on mode = assist light torch not allowed torch = 0 torch allowed mode = torch output on strobe = 1 output on strobe disabled mode = flash output off 0 8028-036 tx_mask enabled tx_mask = 1 en1 = 0 en2 = 1 figure 34. i 2 c interface mode: state transitions
ADP1655 rev. 0 | page 16 of 24 i 2 c register map the lowest bit number (0) represents the least significant bit, and the highest bit number (7) represents the most significant bit. table 8. design information register (register 0x00) bit r/w reset state 7:0 r 00100001 table 9. version register (register 0x01) bit r/w reset state 7:0 r 00000001 table 10. vref and timer register (register 0x02) bit r/w description 7:6 r/w reserved 5:4 r/w number of leds detection comparator reference level 00 = 4.3 v (default) 01 = 4.6 v 10 = 4.0 v 11 = 4.9 v 3:0 r/w flash timer value setting 0000 = 100 ms 0001 = 150 ms 0010 = 200 ms 0011 = 250 ms 0100 = 300 ms 0101 = 350 ms 0110 = 400 ms 0111 = 450 ms 1000 = 500 ms 1001 = 550 ms 1010 = 600 ms 1011 = 650 ms 1100 = 700 ms 1101 = 750 ms 1110 = 800 ms 1111 = 850 ms (default)
ADP1655 rev. 0 | page 17 of 24 table 11. current set register (register 0x03) bit r/w description 7:4 r/w flash current value setting 0000 = 200 ma 0001 = 220 ma 0010 = 240 ma 0011 = 260 ma 0100 = 280 ma 0101 = 300 ma 0110 = 320 ma (default for two leds) 0111 = 340 ma 1000 = 360 ma 1001 = 380 ma 1010 = 400 ma 1011 = 420 ma 1100 = 440 ma 1101 = 460 ma 1110 = 480 ma 1111 = 500 ma (default for one led) 3 n/a 2:0 r/w torch and assist light current value setting 000 = 20 ma 001 = 40 ma (default) 010 = 60 ma 011 = 80 ma 100 = 100 ma 101 = 120 ma 110 = 140 ma 111 = 160 ma table 12. output mode register (register 0x04) bit r/w description 7:6 r/w inductor peak current limit setting 00 = 1.25 a 01 = 1.5 a 10 = 1.75 a (default) 11 = 2.0 a 5 r/w 0 = edge sensitive 1 = level sensitive (default) 4 r/w 0 = torch not allowed 1 = torch allowed (default) 3 r/w 0 = led_out off (default) 1 = led_out on 2 r/w 0 = strobe disabled 1 = strobe enabled (default) 1:0 r/w configures led output mode 00 = standby mode (default) 01 = reserved 10 = assist light mode 11 = flash mode
ADP1655 rev. 0 | page 18 of 24 table 13. fault information register (register 0x05) bit r/w description 7 r 0 = no fault (default) 1 = overvoltage or c out fault 6 r 0 = no fault (default) 1 = short-circuit fault 5 r 0 = no fault (default) 1 = overtemperature fault 4 r 0 = no fault (default) 1 = timeout 850 ms fault 3 r/w 0 = one led 1 = two leds (default) 2 r reserved 1 r 0 = no fault (default) 1 = current limit fault 0 r reserved table 14. input control register (register 0x06) bit r/w description 7:3 reserved 2 r/w 0 = strobe 0 triggers flash in level sensitive mode , strobe 1 > 0 triggers flash in edge sensitive mode 1 = strobe 1 triggers flash in level sensitive mode, strobe 0 > 1 triggers flash in edge sensitive mode (default) 1 r/w 0 = tx_mask function disabled 1 = tx_mask function allowed (default) 0 r reserved
ADP1655 rev. 0 | page 19 of 24 safety features for critical system conditions, such as output overvoltage, flash timeout, led output short circuit, and overtemperature conditions, the ADP1655 has built-in safety mechanisms. if one of the fault conditions occurs, the device shuts down and a corresponding flag is set in the fault information register (register 0x05). in i 2 c interface mode, the system baseband processor can read the fault information register through the i 2 c interface to determine the nature of the fault condition and, consequently, the fault flag is cleared. the device is disabled until the fault information register is cleared. in 2-bit logic interface mode, the i 2 c register readback is not available. to clear a fault, set en1, en2, and torch low. overvoltage fault the ADP1655 contains a comparator at the vout pin that monitors the voltage between vout and sgnd. if the voltage exceeds 9.5 v (typical), the ADP1655 shuts down. in i 2 c mode, bit 7 in the fault information register is read back as high. the ADP1655 is disabled until the fault is cleared, ensuring protec- tion against an open circuit. output capacitor fault if no output capacitor is present at the vout pin when the ADP1655 is enabled for a flash, torch, or assist light event, the part shuts down and bit 7 in the fault information register is read back as high. the ADP1655 is disabled until the fault is cleared. the output capacitor detection scheme does not cause the vout pin to rise above the overvoltage threshold even though the overvoltage flag (bit 7) in the fault information register (register 5) is set. the overvoltage and output capacitor fault flags share a single register bit to reduce the required number of registers. timeout fault if the 2-bit logic interface is used, the maximum duration for flash being enabled (en1/en2 = 1) is preset to 850 ms. if en1 and en2 remain high for longer than 850 ms, ADP1655 is disabled until the fault is cleared (en1, en2, and torch low). in i 2 c mode, if strobe mode is enabled (register 0x04, bit 2), strobe is set to level sensitive mode (register 0x04, bit 5), and if strobe remains high for longer than 850 ms, the timeout fault bit, register 0x05, bit 4), is read back as high. the ADP1655 is disabled until the fault is cleared. overtemperature fault if the junction temperature of the ADP1655 rises above 150c, a thermal protection circuit shuts down the device. in i 2 c mode, bit 5 of the fault information register is read back as high. the ADP1655 is disabled until the fault is cleared. short-circuit fault the led_out pin features short-circuit protection that disables the ADP1655 if it detects a short circuit to ground at the led_out pin. the ADP1655 monitors the led voltage when the led driver is enabled. if the led_out pin remains below the short-circuit detection threshold during startup, a short circuit is detected. bit 6 of the fault information register is read back as high. the ADP1655 is disabled until the fault is cleared. current limit the internal switch limits battery current by ensuring that the peak inductor current does not exceed the programmed limit (current limit is set by bit 6 and bit 7 in the output mode register, register 0x04). if the peak inductor current exceeds the limit, the part shuts down and bit 1 of the fault information register is read back as high. the ADP1655 is disabled until the fault is cleared. amount of led detection the ADP1655 is able to detect the amount of led connected in series between the led_out pin and the pgnd potential. in i 2 c mode, the detection is enabled with bit 3 in the output mode register. the part uses an 80 ma led driver current setting to detect the led forward voltage (vf) with a voltage comparator at the start of a flash, torch, or assist light event. if the detected forward voltage is higher than 4.3 v (typical), bit 3 of the fault information register is read back as high. input undervoltage the ADP1655 includes an input undervoltage lockout circuit. if the battery voltage drops below the 2.4 v (typical) input uvlo threshold, the ADP1655 shuts down. in this case, information in all registers is lost, and when power is reapplied, a power-on reset circuit resets the registers to their default conditions.
ADP1655 rev. 0 | page 20 of 24 applications information external component selection selecting the inductor the ADP1655 boost converter increases the battery voltage to allow driving of one or two leds, whose combined voltage drop is higher than the battery voltage plus the current source headroom voltage. this allows the converter to regulate the led current over the entire battery voltage range and with a wide variation of led forward voltage. the inductor saturation current should be greater than the sum of the dc input current and half the inductor ripple current. a reduction in the effective inductance due to saturation increases the inductor current ripple. suggested inductors are shown in table 15 . table 15. suggested inductors vendor value (h) part no. dcr (m) isat (a) dimensions l w h (mm) toko 2.2 fdse0312 160 3.1 3 3 1.2 toko 2.0 de2812c 67 1.8 3.0 3.2 1.22 coilcraft 2.2 lps3010 220 1.4 3 3 1.0 coilcraft 2.2 lps3314 100 1.5 3 3 1.4 selecting the input capacitor the ADP1655 requires an input bypass capacitor to supply transient currents while maintaining constant input and output voltages. the input capacitor carries the input ripple current, allowing the input power source to supply only the dc current. use an input capacitor with a sufficient ripple current rating to handle the inductor ripple. increased input capacitance reduces the amplitude of the switching frequency ripple on the battery. because of the dc bias characteristics of ceramic capacitors, a 0603, 6.3 v x5r/x7r, 10 f ceramic capacitor is preferable. higher value input capacitors help to reduce the input voltage ripple and improve transient response. maximum input capacitor current is calculated using the following equation: to minimize supply noise, place the input capacitor as close to the vin pin of the ADP1655 as possible. as with the output capacitor, a low esr capacitor is suggested. a list of suggested input capacitors is shown in table 16 . table 16. suggested input capacitors vendor value part no. dimensions l w h (mm) murata 10 f, 6.3 v grm188r60 j106me47 1.6 0.8 0.8 tdk 10 f, 6.3 v c1608jb0j106k 1.6 0.8 0.8 tayio yuden 10 f, 6.3 v jmk107bj106ma 1.6 0.8 0.8 selecting the output capacitor the output capacitor maintains the output voltage and supplies the led current during nfet power switch on period. it also stabilizes the loop. a 10.0 f, 16 v x5r/x7r ceramic capacitor is suggested. note that dc bias characterization data is available from capa- citor manufacturers and should be taken into account when selecting input and output capacitors. 16 v capacitors are recommended for most two-led designs. designs with 1 mm height restrictions can also use 0603 case size, 16 v capacitors in parallel. a list of suggested output capacitors is shown in table 17 . table 17. suggested output capacitors vendor value part no. dimensions l w h (mm) murata 10.0 f, 10 v grm21br71a106ke51 2 1.25 1.25 murata 10.0 f, 16 v grm31c r61c106ka88 3.2 1.6 1.6 tayio yuden 10.0 f, 16 v emk212bj106kg 2 1.25 1.25 higher output capacitor values reduce the output voltage ripple and improve load transient response. when choosing this value, it is also important to account for the loss of capacitance due to output voltage dc bias. ceramic capacitors are manufactured with a variety of dielec- trics, each with different behavior over temperature and applied voltage. capacitors must have a dielectric that ensures the minimum capacitance over the necessary temperature range and dc bias conditions. x5r or x7r dielectrics with a voltage rating of 10.0 v or 16 v are suggested for best performance. y5v and z5u dielectrics are not suggested for use with any dc-to-dc converter because of their poor temperature and dc bias characteristics. in max load cin v ii )( ) ( ?
ADP1655 rev. 0 | page 21 of 24 the worst-case capacitance accounting for capacitor variation over temperature, component tolerance, and voltage is calcu- lated using the following equation: c eff = c out (1 ? tempco ) (1 ? tol ) where: c eff is the effective capacitance at the operating voltage. tempco is the worst-case capacitor temperature coefficient. tol is the worst-case component tolerance. in this example, tempco over ?40c to +85c is assumed to be 15% for an x5r dielectric, tol is assumed to be 10%, and c out is 9.528 f at 1.8 v, as shown in figure 35 . substituting these values in the equation yields c eff = 9.528 f (1 ? 0.15) (1 ? 0.1) = 7.288 f 12 c a pacitance (f) dc bias voltage (v) 10 8 6 4 2 0 0 2 4 6 8 10121416 08028-037 figure 35. dc bias characteristic of a 16 v, 10 f ceramic capacitor to guarantee the performance of the ADP1655, it is imperative that the effects of dc bias, temperature, and tolerances on the behavior of the capacitors be evaluated for each application. the peak-to-peak output voltage ripple for the selected output capacitor and inductor values is calculated using the following equation: () out sw ripple out sw in ripple cf i clf v v = = 8 2 2 capacitors with lower equivalent series resistance (esr) are preferred to guarantee low output voltage ripple, as shown in the following equation: rippl e ripple cout i v esr the effective capacitance needed for stability, which includes temperature and dc bias effects, is 4 f.
ADP1655 rev. 0 | page 22 of 24 pcb layout poor layout can affect performance, causing electromagnetic interference (emi) and electromagnetic compatibility (emc) problems, ground bounce, and voltage losses. poor layout can also affect regulation and stability. a good layout is implemented using the following rules and shown in figure 36 : ? place the inductor, input capacitor, and output capacitor close to the ic using short tracks. these components carry high switching frequencies and large tracks act as antennas. ? route the output voltage path away from the inductor and sw node to minimize noise and magnetic interference. ? maximize the size of ground metal on the component side to help with thermal dissipation. ? use a ground plane with several vias connecting to the component side ground to further reduce noise interfe- rence on sensitive circuit nodes. high power led v in inductor output capacitor input capacitor ADP1655 pgnd high power led pgnd 0 8028-028 figure 36. example layout of the ADP1655 driving two white leds
ADP1655 rev. 0 | page 23 of 24 020409-b outline dimensions a b c d 0.660 0.602 0.544 1.54 1.50 1.46 2.04 2.00 1.96 1 2 3 bottom view (ball side up) top view (ball side down) 0.330 0.310 0.290 1.50 ref seating plane 1.00 ref 0.50 ref 0.380 0.352 0.324 0.280 0.250 0.220 0.04 max coplanarity 0.022 ref ball a1 identifier figure 37. 12-ball wafer level chip scale package [wlcsp] (cb-12-4) dimensions shown in millimeters ordering guide model temperature range package desc ription package option branding ADP1655acbz-r7 1 C40c to +125c 12-ball wafer level chip scale package [wlcsp] cb-12-4 lam ADP1655-evalz 1 evaluation board 1 z = rohs compliant part.
ADP1655 rev. 0 | page 24 of 24 notes ?2009 analog devices, inc. all rights reserved. trademarks and registered trademarks are the prop erty of their respective owners. d08028-0-5/09(0)

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