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general description the MAX1576 charge pump drives up to 8 white leds with regulated constant current for uniform intensity. the main group of leds (led1?ed4) can be driven up to 30ma per led for backlighting. the flash group of leds (led5?ed8) are independently controlled and can be driven up to 100ma per led (or 400ma total). by utilizing adaptive 1x/1.5x/2x charge-pump modes and very-low-dropout current regulators, the MAX1576 achieves high efficiency over the full 1-cell lithium-bat- tery voltage range. the 1mhz fixed-frequency switch- ing allows for tiny external components, and the regulation scheme is optimized to ensure low emi and low input ripple. the MAX1576 uses two external resistors to set the main and flash full-scale (100%) led currents. four control pins are used for led dimming by either serial control or 2-bit logic per group. enm1 and enm2 set the main leds to 10%, 30%, or 100% of full scale. enf1 and enf2 set the flash leds to 20%, 40%, or 100% of full scale. in addition, connect either pair of control pins together for single-wire, serial pulse dim- ming control. the MAX1576 is available in a 24-pin thin qfn, 4mm x 4mm package (0.8mm max height). applications camera phones lcd backlights led camera flashes cell phones and smart phones pdas, digital cameras, and camcorders features ? powers up to 8 leds up to 30ma/led drive for backlight up to 400ma total drive for flash ? 85% average efficiency (p led / p batt ) over li+ battery discharge ? 0.7% typical led current matching ? adaptive 1x/1.5x/2x mode switchover ? flexible brightness control single-wire, serial pulse interface (5% to 100%) 2-bit (3 levels) logarithmic logic ? low input ripple and emi ? low 0.1? shutdown current ? 2.7v to 5.5v supply voltage range ? soft-start limits inrush current ? output overvoltage protection ? thermal-shutdown protection ? 24-pin thin qfn, 4mm x 4mm package MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash ________________________________________________________________ maxim integrated products 1 ordering information t ypical operating circuit 19-3326; rev 0; 6/04 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available part temp range pin-package MAX1576etg -40? to +85? 24 thin qfn 4mm x 4mm (t2444-4) MAX1576 1 f1 f 4.7 f inp in enm1 enm2 enf1 enf2 gnd1 out c1p c1n pgnd gnd2 setf setm c2p flash main c2n 4.7 f 1 f on/off and current setting input 2.7v to 5.5v output up to 480ma led1 led2 led3 led4 led5 led6 led7 led8 pin configuration appears at end of data sheet.
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v in = 3.6v, v gnd1 = v gnd2 = v pgnd = 0v, enm1 = enm2 = enf1 = enf2 = in, r setm = r setf = 6.8k ? , t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. inp, in, out, enm1, enm2, enf1, enf2 to gnd1 .......................................................-0.3v to +6.0v setf, setm, led1, led2, led3, led4, led5, led6, led7, led8 to gnd1 ....................-0.3v to (v in + 0.3v) c1n, c2n to gnd1 ........................................-0.3v to (v in + 1v) c1p, c2p to gnd1 ................ -0.3v to greater of (v out + 1v) or (v in + 1v) gnd2, pgnd to gnd1 .........................................-0.3v to +0.3v out short circuit to gnd ..........................................continuous continuous power dissipation (t a = +70 c) 24-pin thin qfn (derate 20.8mw/ c above +70 c)..............................................................1666mw operating temperature range ...........................-40 c to +85 c junction temperature ......................................................+150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c parameter conditions min typ max units in operating voltage 2.7 5.5 v undervoltage-lockout threshold v in rising or falling 2.25 2.45 2.60 v undervoltage-lockout hysteresis 50 mv overvoltage protection threshold v out rising 5 v 1mhz switching, no load, 1.5x or 2x mode 3.8 6.0 supply current 1x mode 10% setting, led5?ed8 off 0.3 ma shutdown supply current enm1 = enm2 = enf1 = enf2 = gnd 0.1 3 a soft-start time 2ms set_ bias voltage 0.604 v set_ leakage in shutdown enm1 = enm2 = enf1 = enf2 = gnd, v set_ = 0v or v in 0.01 1 a setm current range 40 130 ? setf current range 40 145 ? setm to main led_ current ratio (i led / i setm ) 100% setting, led1? 233 a/a setf to flash led_ current ratio (i led / i setf ) 100% setting, led5? 708 a/a led1? -6 +6 led_ current accuracy led5? -8 +8 % led_ to led_ current matching (note 2) -3.5 ?.7 +3.5 % led1?ed4, r setm = 4.64k ? 27 30 maximum led_ sink current led5?ed8, r setf = 4.12k ? 90 100 ma led_ dropout voltage (note 3) 40 90 mv led_ 1.5x and 2x regulation voltage 150 mv led_ 1x to 1.5x or 1.5x to 2x mode transition threshold 90 100 110 mv input-voltage-mode transition hysteresis 150 mv
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash _______________________________________________________________________________________ 3 note 1: specifications to -40 c are guaranteed by design and not production tested. note 2: led current matching is defined as: (i led_ - i avg ) / i avg . matching is for leds within the main group (led1?ed4) or the flash group (led5?ed8). note 3: dropout voltage is defined as the led_ to gnd_ voltage at which current into led_ drops 10% from the value at v led_ = 0.2v. electrical characteristics (continued) (v in = 3.6v, v gnd1 = v gnd2 = v pgnd = 0v, enm1 = enm2 = enf1 = enf2 = in, r setm = r setf = 6.8k ? , t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter conditions min typ max units led_ leakage in shutdown enm1 = enm2 = enf1 = enf2 = gnd 0.1 2 a charge-pump maximum out current v in 3.15v, v out = 3.9v 480 ma 1x mode, (v in - v out ) / i out 2.5 1.5x mode, (1.5v in - v out ) / i out 5.0 open-loop out resistance 2x mode, (2v in - v out ) / i out 5.0 ? switching frequency 1 mhz en_ high voltage v in = 2.7v to 5.5v 1.6 v en_ low voltage v in = 2.7v to 5.5v 0.4 v en_ input current v en_ = 0v or 5.5v 0.01 1 a en_ low shutdown delay t shdn (see figure 3) 225 470 800 ? en_ t lo (see figure 3) 0.5 250.0 ? en_ t hi (see figure 3) 0.5 ? initial en_ t hi (see figure 3) only required for first en_ pulse 50 ? out pulldown resistance in shutdown enm1 = enm2 = enf1 = enf2 = gnd 5 k ? thermal-shutdown threshold +160 ? thermal-shutdown hysteresis 20 ?
t ypical operating characteristics (v in = 3.6v, en_ = in, circuit of figure 1, r setm = 9.09k ? , r setf = 4.12k ? , t a = +25?, unless otherwise noted.) MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash 4 _______________________________________________________________________________________ efficiency vs. li+ battery voltage driving four main leds MAX1576 toc01 li+ battery voltage (v, time-weighted) efficiency p led / p batt (%) 3.4 3.5 3.6 3.7 3.8 3.9 50 60 70 80 90 100 40 4.2 3.0 15ma/led 4.5ma/led 1.5ma/led efficiency vs. li+ battery voltage driving flash led module MAX1576 toc02 li+ battery voltage (v, time-weighted) efficiency p led / p batt (%) 3.4 3.5 3.6 3.7 3.8 3.9 50 60 70 80 90 100 40 4.2 3.0 160ma total 80ma total 400ma total battery current vs. supply voltage driving four main leds MAX1576 toc03 supply voltage (v) battery current (ma) 3.9 3.6 3.3 3.0 20 40 60 80 100 120 0 2.7 4.2 i led = 15ma i led = 4.5ma i led = 1.5ma v in falling v in rising battery current vs. supply voltage driving flash MAX1576 toc04 supply voltage (v) battery current (ma) 3.9 3.6 3.3 3.0 100 200 300 400 500 600 700 800 900 0 2.7 4.2 i flash = 410ma i flash = 168ma i flash = 81ma input ripple voltage vs. supply voltage with four main leds MAX1576 toc05 supply voltage (v) input ripple (mv rms ) 5.1 4.7 3.9 4.3 3.5 3.1 2 4 6 8 10 12 14 16 18 20 0 2.7 5.5 i led = 4.5ma i led = 1.5ma i led = 15ma input ripple voltage vs. supply voltage with flash and main leds MAX1576 toc06 supply voltage (v) input ripple (mv rms ) 5.1 4.7 3.9 4.3 3.5 3.1 2 4 6 8 10 12 14 16 18 20 0 2.7 5.5 4 main leds at 15ma each i flash = 400ma i flash = 80ma i flash = 160ma led current matching vs. supply voltage with four main leds MAX1576 toc07 supply voltage (v) led current (ma) 5.1 4.7 3.9 4.3 3.5 3.1 14.7 14.9 15.1 15.3 15.5 15.7 15.9 16.1 16.3 16.5 14.5 2.7 5.5 led current vs. ambient temperature with four main leds MAX1576 toc08 ambeint temperature ( c) total led current (ma) 60 35 10 -15 61.1 61.2 61.3 61.4 61.5 61.6 61.7 61.8 61.9 62.0 61.0 -40 85 led current vs. ambient temperature with flash MAX1576 toc09 ambeint temperature ( c) total led current (ma) 60 35 10 -15 161 162 163 164 165 160 -40 85
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash _______________________________________________________________________________________ 5 led current vs. r setm MAX1576 toc10 r setm (k ? ) led current (ma) 10 10 100 1 100 1 100% brightness setting led current vs. r setf MAX1576 toc11 r setf (k ? ) led current (ma) 10 10 100 1 100 1 100% brightness setting operating waveforms (1x mode) MAX1576 toc12 400ns/div v out 50mv/div ac-coupled v in 20mv/div ac-coupled 4 main leds at 20ma each operating waveforms (1.5x mode) MAX1576 toc13 400ns/div v out v out 50mv/div ac-coupled v in v in 20mv/div ac-coupled 4 main leds at 20ma each operating waveforms (2x mode) MAX1576 toc14 400ns/div v out v out 50mv/div ac-coupled v in v in 20mv/div ac-coupled 4 main leds at 20ma each flash at 400ma flash response MAX1576 toc15 400 s/div v en1f v en2f 5v/div 500ma/div 500ma/div 500mv/div ac-coupled i in i out v out 4 main leds at 20ma each. 400ma flash t ypical operating characteristics (continued) (v in = 3.6v, en_ = in, circuit of figure 1, r setm = 9.09k ? , r setf = 4.12k ? , t a = +25?, unless otherwise noted.)
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash 6 _______________________________________________________________________________________ pin description pin name function 1 out output. bypass to ground with a 4.7? ceramic capacitor. connect to the anodes of all the leds. out is internally pulled to ground through a 5k ? resistor during shutdown. 2 enm1 3 enm2 enable and brightness control for led1?ed4 (backlight). see table 1 and figure 3. 4 enf1 5 enf2 enable and brightness control for led5?ed8 (flash). see table 2 and figure 3. 6 led8 7 led7 9 led6 10 led5 flash led_ cathode connection and charge-pump feedback. current flowing into led_ is based on the enf_ logic levels and r setf . the charge pump regulates the lowest led_ voltage to 0.15v. grounding any led_ forces out to operate at approximately 5v. connect led_ to in if this led is not populated. 8g nd2 14 gnd1 ground. connect gnd_ to system ground and the ground side of the input bypass capacitor as close to the ic as possible. 11 led4 12 led3 13 led2 15 led1 main led_ cathode connection and charge-pump feedback. current flowing into led_ is based on the enm_ logic levels and r setm . the charge-pump regulates the lowest led_ voltage to 0.15v. grounding any led_ forces out to operate at approximately 5v. connect led_ to in if this led is not populated. 16 setm bias current set input for led1?ed4. the current flowing out of setm sets the maximum (100%) bias current into each led. setm is internally biased to 0.604v. connect a resistor (r setm ) from setm to ground to set the main led current, r setm = (233 x 0.604) / i led(max) . setm is high impedance during shutdown. 17 setf bias current set input for led5?ed8. the current flowing out of setf sets the maximum (100%) bias current into each led. setf is internally biased to 0.604v. connect a resistor (r setf ) from setf to ground to set the flash led current, r setf = (708 x 0.604) / i led(max) . setf is high impedance during shutdown. t ypical operating characteristics (continued) (v in = 3.6v, en_ = in, circuit of figure 1, r setm = 9.09k ? , r setf = 4.12k ? , t a = +25?, unless otherwise noted.) single-wire dimming response MAX1576 toc16 2ms/div v en1m , v en2m 5v/div 2v/div 50ma/div i out v out line-transient response MAX1576 toc17 40 s/div 1v/div 3v 50ma/div 0 1v/div ac-coupled v in v out i out
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash _______________________________________________________________________________________ 7 detailed description the MAX1576 charge pump drives up to four white leds in the main display for backlighting and up to four white leds for flash with regulated constant current for uniform intensity. by utilizing adaptive 1x/1.5x/2x charge-pump modes and very-low-dropout current reg- ulators, it achieves high efficiency over the 1-cell lithi- um-battery input voltage range. 1mhz fixed-frequency switching allows for tiny external components and low input ripple. 1x to 1.5x switchover when v in is higher than v out , the MAX1576 operates in 1x mode and v out is pulled up to v in . the internal current regulators regulate the led current. as v in drops, v led_ eventually falls below the switchover threshold of 100mv and the MAX1576 starts switching in 1.5x mode. when the input voltage rises above v out by approximately 50mv, the MAX1576 switches back to 1x mode. 1.5x to 2x switchover when v in is less than v out but greater than two-thirds v out , the MAX1576 operates in 1.5x mode. the inter- nal current regulators regulate the led current. as v in drops, v led_ eventually falls below the switchover threshold of 100mv, and the MAX1576 starts switching in 2x mode. when the input voltage rises above two- thirds v out by approximately 50mv, the MAX1576 switches back to 1.5x mode. soft-start the MAX1576 includes soft-start circuitry to limit inrush current at turn-on. once the input voltage is applied, the output capacitor is charged directly from the input with a ramped current source (with no charge-pump action) until the output voltage approaches the input voltage. once this occurs, the charge pump deter- mines if 1x, 1.5x, or 2x mode is required. in the case of 1x mode, the soft-start is terminated and normal opera- tion begins. in the case of 1.5x or 2x mode, soft-start operates until the lowest of led1?ed4 reaches regu- lation. if the output is shorted to ground or is pulled less than 1.25v, the output current is limited by soft-start. true shutdown mode when enm1, enm2, enf1, and enf2 are simultaneously held low, the MAX1576 is shut down after a 0.5ms shut- down delay and the input is isolated from the output. out is internally pulled to gnd with 5k ? during shutdown. thermal shutdown the MAX1576 includes a thermal-limit circuit that shuts down the ic at approximately +160?. turn-on occurs after the ic cools by approximately 20?. applications information setting the main output current setm controls led1?ed4 bias current. current flow- ing into led1, led2, led3, and led4 is a multiple of the current flowing out of setm. i led1 = i led2 = i led3 = i led4 = k x (0.604v / r setm ) true shutdown is a trademark of maxim integrated products, inc. pin description (continued) pin name function 18 in supply voltage input. bypass to ground with a 1? ceramic capacitor. the input voltage range is 2.7v to 5.5v. in is high impedance during shutdown. 19 pgnd power ground. connect pgnd to system ground. pgnd is used for charge-pump switching currents. 20 c1n transfer capacitor 1 negative connection. connect to a 1? ceramic capacitor between c1p and c1n. c1n is internally shorted to in during shutdown. 21 c2n transfer capacitor 2 negative connection. connect to a 1? ceramic capacitor between c2p and c2n. c2n is internally shorted to in during shutdown. 22 inp supply voltage input. bypass to pgnd with a 4.7? ceramic capacitor. the input voltage range is 2.7v to 5.5v. inp is high impedance during shutdown. 23 c2p transfer capacitor 2 positive connection. connect a 1? ceramic capacitor from c2p to c2n. during shutdown, if out > in, c2p is shorted to out, and if out < in, c2p is shorted to in. 24 c1p transfer capacitor 1 positive connection. connect a 1? ceramic capacitor from c1p to c1n. during shutdown, if out > in, c1p is shorted to out, and if out < in, c1p is shorted to in. ?p exposed paddle. connect the exposed paddle to ground. connect pgnd, gnd1, and gnd2 to the exposed paddle directly under the ic.
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash 8 _______________________________________________________________________________________ 0.604v 0.15v selmin error amp1 main control flash control control and reference MAX1576 led5 d5 led6 d6 led7 d7 led8 d8 + + + + gnd2 in in enm1 led1 d1 led2 d2 led3 d3 led4 d4 + + + + gnd1 pgnd input 2.7v to 5.5v 1.25v out ovd output up to 480ma c out 4.7 f c2 1 f c in 4.7 f error amp 3 r setf setf error amp 2 r setm setm enm2 enf1 enf2 c3 1 f c1p inp in c1n c2p c2n c4 1 f 1x/1.5x/2x regulating charge pump figure 1. block diagram and typical application circuit
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash _______________________________________________________________________________________ 9 where k = 23, 70, or 233 (depending upon the state of enm1 and enm2, see table 1), and r setm is the resis- tor connected between setm and ground (see the typical operating circuit ). setting the flash output current setf controls the led5?ed8 bias current. current flowing into led5, led6, led7, and led8 is a multiple of the current flowing out of setf. i led5 = i led6 = i led7 = i led8 = n x (0.604v / r setf ) where n = 142, 283, or 708 (depending upon enf1 and enf2, see table 2), and r setf is the resistor con- nected between setf and ground (see the typical operating circuit ). single-wire pulse dimming for more dimming flexibility or to reduce the number of control traces, the MAX1576 supports serial pulse dim- ming. connect enm1 and enm2 (or enf1 and enf2) together to enable single-wire pulse dimming of the main (or flash) leds. when enm1 and enm2 (or enf1 and enf2) go high simultaneously, the main (or flash) leds are enabled at full brightness. each subsequent low-going pulse (500ns to 250? pulse width) reduces the led current by 10%, so after one pulse the led current is 0.9 x i led_ . the 10th pulse reduces the cur- rent by 5% so the led current reduces from 0.1 x i led_ to 0.05 x i led_ . the 11th pulse sets the led current back to i led_ . figure 3 shows a timing diagram for sin- gle-wire pulse dimming. because soft-start is longer than the initial t hi , apply dimming pulses quickly upon startup (after initial t hi ) to avoid led_ current transition- ing through full brightness. simple on/off control if dimming control is not required, connect enm1 to enm2 (or enf1 to enf2) for simple on/off control. in this case, led current is set by the values of r setm (or r setf ). figure 2. typical application circuit for driving a single high- brightness led MAX1576 1 f1 f 4.7 f inp in pgnd enm1 enm2 enf1 enf2 gnd1 out c1p c1n gnd2 setf setm c2p c2n 4.7 f1 f luxeon ds25 on/off and current setting input 2.7v to 5.5v output up to 480ma led1 led2 led3 led4 led5 led6 led7 led8 figure 3. en_ timing diagram 1 023 45 67 8 910 11 shdn t shdn 0.5ms (typ) 90% 100% 5% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% shdn i led_ enm1 and enm2 or enf1 and enf2 t soft-start initial t hi t lo t hi 50 s 500ns 500ns to 250 s enf1/enf2 states brightness led5?ed8 current enf1 = low, enf2 = low shutdown 0 enf1 = low, enf2 = high 1/5 brightness 142 x i setm enf1 = high, enf2 = low 2/5 brightness 283 x i setm enf1 = high, enf2 = high full brightness 708 x i setm enm1/enm2 states brightness led1?ed4 current enm1 = low, enm2 = low shutdown 0 enm1 = low, enm2 = high 1/10 brightness 23 x i setm enm1 = high, enm2 = low 3/10 brightness 70 x i setm enm1 = high, enm2 = high full brightness 233 x i setm table 1. enm1/enm2 states table 2. enf1/enf2 states
MAX1576 dimming using pwm into enm1 use enm2 for shutdown and drive enm1 with a pwm signal. led brightness can be varied from 1/10 to full brightness based on the duty cycle of the pwm signal. the waveforms in the typical operating characteristics show the response time of dimming. drive enm2 high to keep the ic on, eliminating any soft-start delay that would impede pwm control and allowing a pwm fre- quency up to 5khz ( figure 4). dimming using a dac or filtered pwm both the main leds and flash leds allow dimming using a dac or filtered pwm. use a dac output to sum a current into the set_ node, or use a high-frequency pwm signal to drive an rcr filter on set_ (figure 5). with the component values shown in figure 5, a 0% pwm duty cycle corresponds to 20ma/led, while a 100% pwm duty cycle corresponds to 0ma/led. at pwm frequencies above 5khz, c6 may be reduced. 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash 10 ______________________________________________________________________________________ figure 4. dimming using pwm signal into enm1 MAX1576 1 f1 f 4.7 f inp in enm1 enm2 on off enf1 enf2 gnd1 out c1p c1n pgnd gnd2 setf setm c2p flash main c2n 4.7 f 1 f on/off and current setting input 2.7v to 5.5v output up to 480ma led1 led2 led3 led4 led5 led6 led7 led8 pwm input figure 5. dimming using filtered pwm signal MAX1576 1 f1 f 4.7 f c6 1 f inp in enm1 enm2 enf1 enf2 gnd1 out c1p c1n pgnd gnd2 setf setm c2p flash main c2n 4.7 f 1 f on/off and current setting input 2.7v to 5.5v pwm input 0 to 2.5v output up to 480ma led1 led2 led3 led4 led5 led6 led7 led8 r setm 9.09k ? r2 14.3k ? r1 14.3k ?
driving fewer than 8 leds when driving fewer than 8 leds, two different connec- tion schemes can be used. the first scheme is shown in figures 2 and 6, where led_ is connected to the adjacent led_. this method allows increased current through the led and effectively allows total led current to be i led multiplied by the number of pins connected. the second method of connection is shown in figure 7, where standard white leds are used and fewer than 8 are connected. this scheme does not alter current through each led but ensures that the unused led_ is properly terminated. input ripple for led drivers, input ripple is more important than out- put ripple. input ripple is highly dependent on the source supply? impedance. adding a lowpass filter to the input further reduces input ripple. alternately, increasing c in to 10? cuts input ripple in half with only a small increase in footprint. the 1x mode always has very low input ripple. MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash ______________________________________________________________________________________ 11 figure 6. providing increased led current per led MAX1576 1 f1 f 4.7 f inp in enm1 enm2 enf1 enf2 gnd1 out c1p c1n pgnd gnd2 setf setm c2p flash main c2n 4.7 f 1 f on/off and current setting input 2.7v to 5.5v output up to 480ma led1 led2 led3 led4 led5 led6 led7 led8 figure 7. schematic for when fewer than 8 leds is acceptable MAX1576 1 f1 f 4.7 f inp in enm1 enm2 enf1 enf2 gnd1 out c1p c1n pgnd gnd2 setf setm c2p flash main in in c2n 4.7 f 1 f on/off and current setting input 2.7v to 5.5v output up to 260ma led1 led2 led3 led4 led5 led6 led7 led8
MAX1576 typical operating waveforms shown in the typical operating characteristics show input ripple in 1x, 1.5x, and 2x mode. component selection use only ceramic capacitors with an x5r, x7r, or better dielectric. see table 3 for a list of recommended parts. pc board layout and routing the MAX1576 is a high-frequency switched-capacitor voltage regulator. for best circuit performance, use a solid ground plane and place c in , c out , c2, c3, and c4 as close to the MAX1576 as possible. there should be no vias on c in . connect gnd1, gnd2, and pgnd to the exposed paddle directly under the ic. refer to the MAX1576 evaluation kit for an example. chip information transistor count: 6679 process: bicmos 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash 12 ______________________________________________________________________________________ 19 pgnd 20 c1n 21 c2n 22 inp 23 c2p 24 c1p 1 out 2 enm1 3 enm2 4 enf1 5 enf2 6 led8 18 in 17 setf 16 setm 15 led1 14 gnd1 13 led2 12 led3 11 led4 10 led5 9 led6 8 gnd2 7 led7 MAX1576 thin qfn 4mm x 4mm pin configuration designation value manufacturer part number description c in , c out 4.7? murata grm188r60j475k 4.7? ?0%, 6.3v x5r ceramic capacitors (0603) c2, c3, c4 1? murata grm155r60j105k 1? ?0%, 6.3v x5r ceramic capacitors (0402) d1?4 nichia nscw215t white leds d5 (d5?8) nichia nbcw011t white leds, four leds in one package r setm , r setf as required kamaya 1% resistors table 3. recommended components
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash ______________________________________________________________________________________ 13 package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .) 24l qfn thin.eps c 1 2 21-0139 package outline 12, 16, 20, 24l thin qfn, 4x4x0.8mm
MAX1576 480ma white led 1x/1.5x/2x charge pump for backlighting and camera flash maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 14 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2004 maxim integrated products printed usa is a registered trademark of maxim integrated products. c 2 2 21-0139 package outline 12, 16, 20, 24l thin qfn, 4x4x0.8mm package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation go to www.maxim-ic.com/packages .)

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