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pc112/PC113 version : a.001 issue date : 2004/10/01 file name : sp-pc112/PC113-a.001.doc total pages : 14 step up converter for white led driver ?W@^?I? 9?7?1 silicon touch technology inc . 9-7f-1, prosperity road i, science based industrial park, hsin-chu, taiwan 300, r.o.c. tel 886-3-5645656 fax 886-3-5645626
c???? silicon touch technology inc. - 1 - version a.001 pc112/PC113 general description pc112/PC113 is a compact, high-efficienc y step-up dc-dc converter which drives 2-6 series white leds with c onstant current from 3v to 5v. extremely low shutdown power supply current ensures the high effi ciency of battery system. the PC113 works at 500khz, allowing the application of tiny external components. low feedback voltage and hence minimal input current from the ba ttery extends battery life. built-in n-channel power switches optimiz e the layout area of pcb. since pc112/PC113 drives series leds, it regulates the light intensity uniformly. with a single external resistor or pwm signal, users can easily set the led current and led brightness. while output loading is open, likes the case of leds failure, the duty cycle of the dc-dc converter will increase rapidly, caus ing high output voltage to damage the circuit. to avoid this situation, a z ener diode should be connected to the dc-dc converter?s output to clamp the output voltage in most applications. however, PC113 has built-in the over-voltage protection circ uit to protect the output circuit and thus eliminates the need of the external zener diode. pc112/PC113 is also characte rized of the soft-start feat ure, which limits the inrush current. it is available in thin-sot type package. features 1. typical 85% efficiency 2. no external power switch 3. low shutdown supply current 4. low feedback voltage 5. drives 6 white leds 20m a from working voltage 2.0v 6. 4 % led output current accuracy 7. over voltage protection circuit build in(PC113) 8. soft-start circuit build in 9. thin 6-pin sot23-6 package application 1. white led display backlighting 2. cellular telephones 3. personal digital assistant 4. digital cameras 5. portable machine
c???? silicon touch technology inc. - 2 - version a.001 pc112/PC113 block diagram 4 3 fb en 5 vdd lx 1 2 vss amp 0.1v clock genertor pre- driver control logic soft start cmp ovp 5 - + ovp 4 3 fb en 5 vdd lx 1 2 vss amp 0.5v clock genertor pre driver control logic soft start cmp PC113 pc112 pin descriptions pin no PC113 pc112 pin name descriptions 1 1 lx connect inductor to battery 2 2 vss ground pin 3 3 fb feedback pin 4 4 en enable pin 5 ovp over voltage protection 6 5 vdd input voltage supply pin siti PC113 vdd lx en vss fb 1 2 34 6 5 ovp siti pc112 vdd lx en vss fb 1 2 34 5 topview
c???? silicon touch technology inc. - 3 - version a.001 pc112/PC113 absolute maximum ratings param eter symbol rating unit supply voltage vdd 5.5 v lx voltage v lx 24 v en voltage v en 5.5 v power dissipation p d 2.5 mw storage temperature t stg -65~140 o c operating temperature t opr -40~120 o c junction temperature tj 160 o c electrical characteristics , v dd =3.6v, t a = 25 o c . (unless otherwise specified) parameter symbol condition min typ max unit operating input volt age vdd 2.8 3.6 5 v fb pin voltage v fb 85 95 105 mv fb vol. temp. coefficient t fb i led = 20ma +92 v/c switch-on resistance r sw 1.5 ? switch max on-time t on 1.4 1.5 1.6 s maximum duty cycle d max 80 % switching frequency f sw 450 500 550 khz efficiency 85 % i dd v en =high 1 ma supply current i ddq v en =low 0.1 a v en =high 0.2 ma shutdown input current i en v en =low 10 na *over voltage protection v p 23 v *note1 : only PC113 build this function
c???? silicon touch technology inc. - 4 - version a.001 pc112/PC113 typical application circuit siti pc112 vdd lx vss on v in 2.8 to 5.0v l1 6.8uh d1 mbr0520 c3 1uf fb off en c1 4.7 uf c2 4.7 uf r 1 22 i in r3 1k zener r2 5.6 fig. 1 application circuit of pc112 siti PC113 vdd lx vss on v in 2.8 to 5.0v l1 6.8uh d1 mbr0520 c3 1uf white led x 3 fb off en c1 4.7 uf c2 4.7 uf r 1 22 i in i led 20ma r 2 ovp 5.6 fig. 2 application circuit of PC113
c???? silicon touch technology inc. - 5 - version a.001 pc112/PC113 typical performance characteristics r 1 =22 ? , l1=6.8 h , c1=4.7 f , c2=4.7 f , c3=1 f , schottky diode vf=0.18, t a = 25 o c , (unless otherwise specified) 5 10 15 20 25 30 0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0.89 efficiency vs load current efficiency (%) load current (ma) vin=2.85v vin=3.6v vin=4.2v 5 10 15 20 25 30 0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 efficiency vs load current efficiency (%) load current (ma) vin=2.85v vin=3.6v vin=4.2v 5 10 15 20 25 30 0.78 0.79 0.8 0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 efficiency vs load current efficiency (%) load current (ma) vin=2.85v vin=3.6v vin=4.2v 5 10 15 20 25 30 0.09 0.092 0.094 0.096 0.098 0.1 0.102 0.104 0.106 0.108 0.11 feedback voltage vs load current feedback voltage (v) load current (ma) 2x leds 3x leds 4x leds -40 -20 0 20 40 60 80 100 120 140 78 79 80 81 82 83 84 85 efficiency vs temperature (high load) efficiency (%) temperature (degree) vin=2.85v vin=3.6v vin=4.2v 3 wleds, 25ma -40 -20 0 20 40 60 80 100 120 140 76 77 78 79 80 81 82 83 84 efficiency vs temperature (light load) efficiency (%) temperature (degree) vin=2.85v vin=3.6v vin=4.2v 3 wleds, 5ma 2leds 3leds 4leds
c???? silicon touch technology inc. - 6 - version a.001 pc112/PC113 typical performance characteristics (cond.) 5 10 15 20 25 30 0.088 0.09 0.092 0.094 0.096 0.098 0.1 feedback voltage vs load current feedback voltage (v) load current (ma) 2x leds 3x leds 4x leds -20 0 20 40 60 80 100 120 420 440 460 480 500 520 540 560 frequency vs temperature frequency (khz) temperature (degree) note1 :the white led forward voltage is about 3.6v, so pc112/PC113 could drive up to 6 series white leds. note2 : to chose d1(schottky diode), it must has fast switch characteristics and low forward voltage. we recommend the mbr0520in this application. note3 : the ripple of input voltage could be minimized with c1. thus, a large value of capacitor c1 is suggested. with the applic ation of a rc-filter (r1 and c2) to vdd pin, the stability of circuit is enhanced. t he ripple of output voltage also could be improved with c3. in most designs, the lo w esr (equivalent series resistance) capacitors are desirable, like multi-layer capacitor. a 1uf to 2.2uf output capacitor is sufficient for most applications. note4 : i led = 2 095 . 0 r (a)
c???? silicon touch technology inc. - 7 - version a.001 pc112/PC113 application information reference fig.1 ,condition: zener=15v, ta = 25 o c , unless otherwise specified lx vo vdd (ac) i in lx en i in i in en vo v fb en i in vo vo
c???? silicon touch technology inc. - 8 - version a.001 pc112/PC113 general description bias current setting the pc112/PC113 is a dc/dc converter wh ich provides a regul ated current output from a vdd input of dc 2.8v to 5.0v. regulating the led current can be achieved by setting the resistor of fb pin to ground. so the value of the current setting resistor r2 could be set by: r2= led i 095 . 0 ( ) brightness control the brightness control can be achieved by applying a pwm control signal to en pin or by varying the current setting resistor r2, shown as follows. PC113 pwm en 5 PC113 pwm fb 4 r min r incr PC113 v adj fb 4 r a r 2 r b to leds fig. 3 fig. 4 fig. 5 we could apply a digital pwm signal (100hz~ 3khz) to en pin (fig. 3) to generate a led current waveform identical to that of the pwm signal waveform. the average output led current is calculated: i led = 2 095 . 0 r x duty of pwm (a) another control method is to vary the val ue of the current setting resistor (fig. 4). i led = 2 095 . 0 r which r2 = incr min incr min r r r r + , pwm is high (a) a dac can also be applied for brightness c ontrol, which is shown in fig. 5. if v adj
c???? silicon touch technology inc. - 9 - version a.001 pc112/PC113 (output of a dac or ambient light sensor) increases, the output voltage will decrease. for example, r a =6.2k , r b =82k , v adj = 4v, v fb1 will set to 0.05v, so the led?s current will be half . open circuit protection (PC113 only) when the leds are disconnected from the circuit or the leds fail, PC113 will switch to maximum duty cycle. this situat ion results in a high output voltage and may cause the lx pin voltage to exceed its maximum rating of 24v and thus damages output circuit. normally, a zener diode is app lied to clamp the high voltage; however, PC113 has built-in the over-voltage protecti on circuit, and thus no external component is required. recommended pcb layout 1. c2 is placed as close to pc112/113 as possible. 2. minimize the length and area of all traces connecting to lx pin. 3. the power path : vdd l1 lx d1 c3 should be kept as short as possible to avoid emi. 4. fig. 6 shows the exemplary test board layout. (reference page4. typical application circuit ) fig. 6
c???? silicon touch technology inc. - 10 - version a.001 pc112/PC113 recommended solder pad 3.1 mm 1.9 mm 1.6mm 0.35mm fig. 7
c???? silicon touch technology inc. - 11 - version a.001 pc112/PC113 package specification (sot23-6) dimensions in millimeters symbol min nom max a 1.00 1.10 1.30 a 1 0.00 0.10 a 2 0.70 0.80 0.90 b 0.35 0.40 0.50 c 0.10 0.15 0.25 d 2.70 2.90 3.10 e 1.40 1.60 1.80 e 1.90(typ) h 2.60 2.80 3.00 l 0.37 1 1 5 9 d e h b a 1 e a a 2 1 c l
c???? silicon touch technology inc. - 12 - version a.001 pc112/PC113 package specification (sot23-5) dimensions in millimeters symbol min nom max a 1.00 1.10 1.30 a 1 0.00 0.10 a 2 0.70 0.80 0.90 b 0.35 0.40 0.50 c 0.10 0.15 0.25 d 2.70 2.90 3.10 e 1.40 1.60 1.80 e 1.90(typ) h 2.60 2.80 3.00 l 0.37 1 1 5 9 d e h b a 1 e a a 2 1 c l
c???? silicon touch technology inc. - 13 - version a.001 pc112/PC113 the products listed herein are designed for ordina ry electronic applications , such as electrical appliances, audio-visual equipment, communicati ons devices and so on. hence, it is advisable that the devices should not be used in medical instruments, surgical implants, aerospace machinery, nuclear power control systems, disa ster/crime-prevention equipment and the like. misusing those products may direct ly or indirectly endanger human life, or cause injury and property loss. silicon touch technology, inc. will not take an y responsibilities regarding the misusage o f the products mentioned above. anyone who purchas es any products described herein with the above-mentioned intention or with such misused applications should accept full responsibility and indemnify. silicon touch technology, inc. a nd its distributors and all their officers and employees shall defend jointly an d severally against a ny and all claims and litigation and all damages, cost and expenses associated with such intention and manipulation.

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