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september 2011 ? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 FAN5345 ? series boost led driver with single-wire digital interface FAN5345 series boost led driver with single-wire digital interface features ? asynchronous boost converter ? drives leds in series: ? FAN5345s20x: 20v output ? FAN5345s30x: 30v output ? 2.5v to 5.5v input voltage range ? single-wire digital control interface to set led brightness levels ? 32 linear steps ? 1.2mhz fixed switching frequency ? soft-start capability ? input under-voltage lockout (uvlo) ? output over-voltage protection (ovp) ? short-circuit detection ? thermal shutdown (tsd) protection ? small form-factor 6-lead ssot23 package applications ? cellular mobile handsets ? mobile internet devices ? portable media players ? pda, dsc, mp3 players description the FAN5345 is an asynchronous constant-current led driver that drives leds in series to ensure equal brightness for all the leds. FAN5345s20x has an output voltage of 20v and can drive up to 5 leds in series. FAN5345s30x has an output voltage of 30v and drive up to 8 leds in series. optimized for small form-factor applications, the 1.2mhz fixed switching frequenc y allows the use of small inductors and capacitors. the FAN5345 uses a simple single-wire digital control interface to program the brightness levels of the leds in 32 linear steps by applying digital pulses. for safety, the device features integrated over-voltage, over- current, short-circuit detection, and thermal-shutdown protection. in addition, input under-voltage lockout protection is triggered if the battery voltage is too low. the FAN5345 is available in a 6-lead ssot23 package. it is ?green? and rohs compliant. (please see http://www.fairchildsemi.com/c ompany/green/index.html for fairchild?s definition of green). ordering information part number output voltage option temperature range package FAN5345s20x 20v -40 to 85c 6-lead, super-sot?-6, jedec mo-193, 1.6mm wide (ma06a) FAN5345s30x 30v .
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 2 FAN5345 ? series boost led driver with single-wire digital interface typical application diagram figure 1. typical application block diagram figure 2. functional block diagram
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 3 FAN5345 ? series boost led driver with single-wire digital interface pin configuration 1 2 3 6 5 4 sw vout en vin gnd fb figure 3. pin assignments top view pin definitions pin # name description 5 vout boost output voltage . output of the boost regulator. connect the leds to this pin. connect c out (output capacitor) to gnd. 1 vin input voltage . connect to power source and decouple with c in to gnd. 4 en enable brightness control . program dimming levels by driving pin with digital pulses. 3 fb voltage feedback . the boost regulator regulates this pin to 0.250v to control the led string current. tie this pin to a current setting resistor (r set ) between gnd and the cathod e of the led string. 6 sw switching node . tie inductor l1 from vin to sw pin. 2 gnd ground . tie directly to a gnd plane.
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 4 FAN5345 ? series boost led driver with single-wire digital interface absolute maximum ratings stresses exceeding the absolute maximum ratings may damage th e device. the device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. in addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. the absolute maximum ratings are stress ratings only. symbol parameter min. max. unit v in vin pin -0.3 6.0 v v fb , v en fb, en pins -0.3 v in + 0.3 v v sw sw pin FAN5345s20x -0.3 22.0 v FAN5345x30x -0.3 33.0 v v out vout pin FAN5345s20x ?0.3 22.0 v FAN5345x30x -0.3 33.0 v esd electrostatic discharge protection human body model per jesd22-a114 1.5 kv charged device model per jesd22-c101 1.5 t j junction temperature -40 +150 c t stg storage temperature -65 +150 c t l lead soldering temperature, 10 seconds +260 c recommended operating conditions the recommended operating conditions table defines the condit ions for actual device operation. recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. fairchild does not recommend exceeding them or designing to absolute maximum ratings. symbol parameter comments min. max. unit v in v in supply voltage 2.5 5.5 v v out v out voltage (1) FAN5345s20x 6.2 18.5 v FAN5345s30x 6.2 28.5 i out v out load current 5 25 ma t a ambient temperature -40 +85 c t j junction temperature -40 +125 c note: 1. the application should guarantee t hat minimum and maximum duty cycle should fall between 20-85% to meet the specified range. thermal properties junction-to-ambient thermal resistance is a function of application and board layout. this data is measured with four-layer 2s2 p boards in accordance to jedec standard jesd51. special at tention must be paid not to exceed junction temperature t j(max) at a given ambient temperature t a . symbol parameter typical unit ? ja6 junction-to-ambient thermal resistance, ssot23-6 package 151 c/w
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 5 FAN5345 ? series boost led driver with single-wire digital interface electrical specifications v in = 2.5v to 5.5v and t a = -40c to +85c unless otherwise noted. typical values are at ta = +25c and v in = 3.6v. symbol parameter conditions min. typ. max. unit power supplies i sd shutdown supply current en = gnd 0.30 0.90 ? a i q(active) quiescent current at i load = 0ma device not switch ing, no load 300 ? a v uvlo under-voltage lockout threshold v in rising 2.10 2.35 2.60 v v in falling 1.80 2.05 2.30 v uvhyst under-voltage lockout hysteresis 250 mv en: enable pin v ih high-level input voltage 1.2 v ? v il low-level input voltage 0.4 v ? r en en pull-down resistance 200 300 400 k ? t lo en low time for dimming (3) v in = 3.6v; figure 28 0.5 300 s t hi delay between steps (3) v in = 3.6v; figure 28 0.5 s t sd en low, shutdown pulse width v in = 3.6v; from falling edge of en 1 ms feedback and reference v fb feedback voltage i led = 20ma from -40c to +85c, 2.7v v in 5.5v 230 250 270 mv i fb feedback input current v fb = 250mv 0.1 1.0 ? a power outputs r ds(on)_q1 boost switch on resistance v in = 3.6v, i sw = 100ma 600 m ? v in = 2.5v, i sw = 100ma 650 i sw(off) sw node leakage (2) en = 0, v in = v sw = v out = 5.5v, v led = 0v 0.1 2.0 ? a i lim-pk boost switch peak current limit FAN5345s20x: v in = 3.2v to 4.3v, t a = 20c to +60c, v f = 3.4v, 4 leds 200 300 400 ma FAN5345s30x 500 750 1000 oscillator f sw boost regulator switching frequency 0.95 1.15 1.35 mhz output and protection v ovp boost output over-voltage protection FAN5345s20x 18.0 20.0 21.5 v FAN5345s30x 27.5 30.0 32.5 ovp hysteresis FAN5345s20x 0.8 FAN5345s30x 1.0 v tlsc v out short-circuit detection threshold v out falling v in ? 1.4 v v thsc v out short-circuit detection threshold v out rising v in ? 1.2 v d max maximum boost duty cycle (3,4) 85 % d min minimum boost duty cycle (3,4) 20 t tsd thermal shutdown 150 c t hys thermal shutdown hysteresis 35 c notes: 2. sw leakage current includes the leakage current of two internal switches; sw to gnd and sw to v out . 3. not tested in production; guaranteed by design. 4. application should guarantee that minimum and maximum du ty cycle fall between 20-85% to meet the specified range.
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 6 FAN5345 ? series boost led driver with single-wire digital interface typical characteristics v in = 3.6v, t a = 25 ? c, i led = 25ma, l = 10h, c out = 1.0f, and c in = 10.0f. 50% 60% 70% 80% 90% 5 10152025 efficiency led current (ma) v in=2.5v v in=2.7v v in=3.6v v in=4.2v vin=4.5v 50% 60% 70% 80% 90% 5 10152025 efficiency led current (ma) v in=2.5v v in=2.7v v in=3.6v vin=4.2v vin=4.5v figure 4. 3 leds: efficiency vs. led current vs. input voltage figure 5. 4 leds: efficiency vs. led current vs. input voltage 50% 60% 70% 80% 90% 5 10152025 efficiency led current (ma) v in=2.5v vin=2.7v v in=3.6v vin=4.2v v in=4.5v 50% 60% 70% 80% 90% 5 10152025 efficiency led current (ma) v in=2.5 v v in=2.7 v v in=3.6 v v in=4.2 v vin=4.5v figure 6. 5 leds: efficiency vs. led current vs. input voltage figure 7. 6 leds: efficiency vs. led current vs. input voltage 50% 60% 70% 80% 90% 5 10152025 efficiency led current (ma) v in=2.5v v in=2.7v vin=3.6v v in=4.2v v in=4.5v 50% 60% 70% 80% 90% 5 10152025 efficiency led current (ma) vin=2.9v v in=3.6v vin=4.2v v in=4.5v figure 8. 7 leds: efficiency vs. led current vs. input voltage figure 9. 8 leds: efficiency vs. led current vs. input voltage
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 7 FAN5345 ? series boost led driver with single-wire digital interface typical characteristics v in = 3.6v, t a = 25 ? c, i led = 25ma, l = 10h, c out = 1.0f, and c in = 10.0f. 50% 60% 70% 80% 90% 2.5 3.0 3.5 4.0 4.5 efficiency input voltage (v) -40c +25c +85c 50% 60% 70% 80% 90% 2.5 3.0 3.5 4.0 4.5 efficiency input voltage (v) -40c +25c +85c figure 10. efficiency vs. input voltage vs. temperature for 5 leds in series figure 11. efficiency vs. input voltage vs. temperature for 7 leds in series -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 2.5 3.0 3.5 4.0 4.5 delta feedback (mv) input voltage (v) -40c +25c +85c 1000 1050 1100 1150 1200 1250 2.5 3.0 3.5 4.0 4.5 frequency (khz) input voltage (v) -40c +25c +85c figure 12. delta of v fb over input voltage and temperature for 7 leds with l=10h and c out =1.0f figure 13. frequency vs. input voltage vs. temperature 18.5 19.0 19.5 20.0 20.5 21.0 2.5 3.0 3.5 4.0 4.5 ovp (v) input voltage (v) 5 leds l = 10h c out = 1.0f i led = 25ma 29.0 29.5 30.0 30.5 31.0 31.5 2.5 3.0 3.5 4.0 4.5 ovp (v) input voltage (v) 7 leds l = 10h c out = 1.0f i led = 25ma figure 14. ovp vs. input voltage: FAN5345s20x figure 15. ovp vs. input voltage: FAN5345s30x
? 2011 fairchild semiconductor corp oration www.fairchildsemi.com FAN5345 ? rev. 1.0.0 8 FAN5345 ? series boost led driver with single-wire digital interface typical characteristics v in = 3.6v, t a = 25 ? c, i led = 25ma, l = 10h, c out = 1.0f, and c in = 10.0f. figure 16. shutdown current vs. input voltage figure 17. quiescent current vs. input voltage figure 18. dimming operation figure 19. line transient r esponse for 5 leds figure 20. line transient response for 6 leds figure 21. line transient response for 7 leds 0.00 0.20 0.40 0.60 0.80 2.50 3.00 3.50 4.00 4.50 shutdown ? current ? (a) v in (v) 225 230 235 240 245 250 255 260 265 2.50 3.00 3.50 4.00 4.50 quiescent ? current ? (a) v in (v)
? 2011 fairchild semiconductor corp oration www.fairchildsemi.com FAN5345 ? rev. 1.0.0 9 FAN5345 ? series boost led driver with single-wire digital interface typical characteristics v in = 3.6v, t a = 25 ? c, i led = 25ma, l = 10h, c out = 1.0f, and c in = 10.0f. figure 22. startup waveform for switch voltage, inductor current, v fb , and en for 5 leds figure 23. steady-state waveform for v out , switch voltage, and i nductor current for 5 leds figure 24. startup waveform for switch voltage, inductor current, v fb , and en for 6 leds figure 25. steady-state waveform for v out , switch voltage, and i nductor current for 6 leds figure 26. startup waveform for switch voltage, inductor current, v fb , and en for 7 leds figure 27. steady-state waveform for v out , switch voltage, and i nductor current for 7 leds
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 10 FAN5345 ? series boost led driver with single-wire digital interface circuit description overview the FAN5345 is an inductive current-mode boost serial led driver that achieves led current regulation by maintaining 0.250v across the r set resistor. the current through the led string (i led ) is therefore given by: set led r i 250 . 0 ? (1) the voltage v out is determined by the sum of the forward voltages across each led, plus the voltage across r set , which is always 250mv. uvlo and soft-start if en has been low for more than 1ms, the ic may initiate a ?cold start? soft-start cycle when en rises, provided v in is above the uvlo threshold. driving eight leds in series FAN5345s30x can drive 8 leds in series, but the minimum input voltage (v in ) must be greater than or equal to 2.9v while the forward voltage of the white led should be less than or equal to 3.2v and t he maximum led current cannot exceed 20ma in order to maintain stable operation. digital interface the FAN5345 implements a single-wire digital interface to program the led brightness to one of thirty-two (32) levels spaced in linear steps. with this single-wire solution, the FAN5345 does not require the syst em processor to constantly supply a signal to drive the leds. digital dimming control the FAN5345 starts driving the leds at the maximum brightness level. after startup, the control logic is ready to accept programming pulses to decrease the brightness level by the number of positive edges applied to the en pin. figure 28. digital pulse-dimming control diagram shows the digital pulse dimming control. the dimming control function has no effect before soft-start finishes. the soft-start takes about 2ms. over-current and short-circuit detection the boost regulator employs a cycle-by-cycle peak inductor current limit of 300ma (typical) and 750ma (typical) for FAN5345s20x and FAN5345s30x respectively. over-voltage / open-circuit protection if the led string is an open circuit, fb remains at 0v and the output voltage continues to increase in the absence of an over-voltage protection (ovp) circuit. the FAN5345s20x ovp circuit disables the boost regulator when v out exceeds 20.0v and continues to keep the regulator off until v out drops below 19.0v. for FAN5345s30x, the ovp is 30.0v and it turns back on when v out is below 29.0v. thermal shutdown when the die temperature exceeds 150c, a reset occurs and remains in effect until the die cools to 115c; at which time, the circuit is allowed to begin the soft-start sequence. figure 28. digital pulse- dimming control diagram
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 11 FAN5345 ? series boost led driver with single-wire digital interface application information the reference schematic diagram is shown in figure 29. FAN5345 is able to drive up to eight leds with input voltage equal or greater than 2.9v (v in 2.9v). however, the number of leds that can be used depends on forward voltage. it is recommended t hat the forward voltage (v f ) of the white leds be no greater than 3.2v and the maximum led current is 20ma. FAN5345 can be also used as a boost convertor by connect the v out point to the load directly. the return trace of the load should also return to gnd through a sense resistor (r1). figure 29. reference application schematic diagram component placement and pcb recommendations figure 30. reference pcb layout FAN5345 switches at 1.2mhz to boost the output voltage. component placement and pcb layout need to be carefully taken into consideration to ensure stable output and to prevent generation of noise. figure 30 is the FAN5345 a portion of the evaluation board layout. the critical layout elements are: the l1, c in , c in return trace, c out , and the c out return trace. input capacitor and return trace the input capacitor is the first priority in a switching buck or boost regulator layout. a stable input source (v in ) enables a switching regulator to deliver its best performance. during the regulator?s operation, it is switching at a high frequency, which makes the load of c in change dynamically to make the input source vary at the same switching frequency as the regulator. to ensure a stable input source, c in needs to hold enough energy to minimize the variation at the input pin of the regulator. for c in to have a fast response of charge / discharge, the trace from c in to the input pin of the regulator and the return trace from gnd of the regulator to c in should be as short and wide as possible to minimize trace resistance, inductance, and c apacitance. during operation, the current flow from c in through the regulator to the load and back to c in contains high-frequency variation due to switching. trace resistance reduces the overall efficiency due to i 2 r loss. even a small trace inductance could effectively yield ground variation to add noise on v out . the input capacitor should be placed close to the vin and gnd pins of the regulator and traces should be as short as possible. avoid routing the return trace through different layers because vias have strong inductance effect at high frequencies. if routing to othe r pcb layers is unavoidable, place vias next to the vin and gnd pins of the regulator to minimize the trace distance.
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 12 FAN5345 ? series boost led driver with single-wire digital interface output capacitor and return trace the output capacitor serves t he same purpose as the input capacitor, but also maintains a stable output voltage. as explained above, the current travels to the load and back to the c out gnd terminal. c out should be placed close to the vout pin. the traces of c out to l1, vout, and return from load to c out should be as short and wide as possible to minimize trace resistance and inductance. to minimize noise coupling to load, a small-value capacitor can be placed between vout and c out to route high-frequency noise back to gnd before it gets to the load. inductor inductor (l1) should be placed as close to the regulator as possible to minimize trace resistance and inductance for the reasons explained above. sense resistor the sense resistor provides a feedback signal for the regulator to control output voltage. a long trace from the sense resistor to the fb pin couples noise into the fb pin. if noise is coupled into the fb pi n, it causes unstable operation of the switching regulator, which affects application performance. the return trace from the sense resistor to the fb pin should be short and away from any fast-switching signal traces. the ground plane under the return trace is necessary. if the ground plan under the return trace is noisy, but not the same ground plane as the regulator; the noise could be coupled into the fb pin through pcb parasitic capacitance, yielding noisy output. in figure 30; c in , c out , and l1 are all placed next to the regulator. all traces are on the same layer to minimize trace resistance and inductance. total pcb area, not including the sense resistor, is 67.2mm 2 (7.47mm x 8.99mm) . table 1. recommended external components part number manufacturer inductor (l) 10.0h lqh43mn100k03 murata nlcv32t-100k-pfr tdk vlf3010at-100mr49-1 tdk dem2810c 1224-as-h-100m toko minimum c out 1.0f cv105x5r105k25at avx/kyocera minimum c in 10.0f grm21br71a106ke51l murata schottky diode n/a rbs520s30 fairchild semiconductor n/a rb520s-30 rohm
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 13 FAN5345 ? series boost led driver with single-wire digital interface physical dimensions figure 31. 6-lead, supersot?- 6, jedec mo-193, 1.6mm wide package drawings are provided as a service to customers considering fairchild component s. drawings may change in any manner wit hout notice. please note the revision and/or date on the drawing and contact a fairchild semi conductor representative to verify or o btain the most recent revision. package specifications do not expand the terms of fairchild?s worldwide terms and conditions, specifically the warranty therein, which covers fairchild products. always visit fairchild semiconductor?s online packagi ng area for the most recent package drawings: http://www.fairchildsemi.com/packaging/ .
? 2011 fairchild semiconductor corporation www.fairchildsemi.com FAN5345 ? rev. 1.0.0 14 FAN5345 ? series boost led driver with single-wire digital interface

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