ts19371 boost (step-up) wled driver with ovp 1/10 version: g08 sot - 2 6 sop - 8 general description the ts19371 is a step-up dc/dc converter specifical ly designed to drive white leds with a constant cur rent. the device can drive up to 126 leds (9s14p) from a 12v supply. the output capacitor can be as small as 4.7 f, saving space versus alternative solutions. a low 95 mv feedback voltage minimizes power loss for better efficiency. additional feature include over output voltage limiting (sot-26 package) when leds are dis connected. the ts19371 switches at a fixed frequency of 1.2mhz , allowing the use of tiny, low profile inductors a nd capacitors to minimize footprint and cost in space consideration applications for cellular phone backl ighting or other hand held equipment. features inherently matched led current high efficiency: 89% typical drives up to 9 leds series @ vin 9~15v drives up to 126 leds (9s14p) @ vin 12~15v drives up to 6 (1w) leds series @ vin 12v over output voltage protection 30v (sot-26) fast 1.2mhz switching frequency requires only 4.7f output capacitor pwm dimming control 1khz to 10khz analog dimming control ordering information part no. package packing ts19371cx6 rf sot-26 3kpcs / 7 reel ts19371cs rl sop-8 2.5kpcs / 13 reel input voltage vs. efficiency application cellular phones portable electronics devices pda, gps lcd display module white led backlighting mr-16 lighting typical application circuit pin definition : 1. sw 6. vin 2. gnd 5. ovp 3. fb 4. ctrl pin definition : 1. vin 8. sw 2. gnd 7. gnd 3. gnd 6. gnd 4. ctrl 5. fb
ts19371 boost (step-up) wled driver with ovp 2/10 version: g08 absolute maximum rating parameter symbol limit unit input voltage v in 20 v supply voltage (recommended) v in 2.5 ~ 18 v fb voltage v fb 10 v sw voltage v sw 36 v ctrl voltage v ctrl 10 v ambient temperature range t a -40 to +85 o c junction temperature range t j -40 to +125 o c electrical specifications (ta = 25 o c, v in = v ctrl =3v, c in =1uf, c out =0.22uf unless otherwise noted) parameter symbol test conditions min typ max units input voltage range v in 2.5 -- 18 v feedback voltage v fb i sw =180ma, vin=5v 80 95 110 mv fb pin bias current i b 10 45 100 na supply current i q -- 2.1 3.0 ma ctrl = 0v -- 0.1 1.0 ua switching frequency f rsw 0.8 1.2 1.6 mhz switch current limit i cl -- 650 -- ma maximum duty cycle d tmx 85 90 -- % switch v cesat v sat at i sw = 250ma -- 350 -- mv switch leakage current i lkg v sw = 5v -- 0.01 5 a voltage enable control v ctl high 1.5 -- -- v low -- -- 0.4 v ctrl pin bias current i ctl ctrl = 2v -- 65 -- a over voltage protection ovp -- 30 -- v thermal resistance - junction to ambient r ? ja sot-26 -- 220 -- c/w sop-8 (note 1) -- 70 -- note 1: surface mounted on 1 x 1 fr4 board note 2: absolute maximum ratings are limits beyond which da mage to the device may occur. note 3: the maximum allowable power dissipation is a funct ion of maximum function temperature, tj(max), the junction to ambient thermal resistance, ja, and the ambient temperature. the maximum allowa ble, power dissipation at any ambient temperature is calculate d using: pd(max)= [tj(max)-ta]/ ja . exceeding the maximum allowable power dissipation will cause excessive di e temperature. all limits at temperature extremes a re guaranteed via correlation using standard statistic al methods
ts19371 boost (step-up) wled driver with ovp 3/10 version: g08 functional block pin description pin (sot-26) pin (sop-8) function description 1 8 sw switching pin. this is the collector of the interna l npn power switch. connect to inductor and diode. minimize the metal t race area connected to this pin to reduce emi. 2 2,3,6,7 ground ground pin. connect directly to lo cal ground plane. 3 5 fb feedback pin. reference voltage is 95mv. connect le ds and a resistor at this pin. led current is determined by the resistance and ctrl voltage. 4 4 ctrl shutdown pin and dimming control pin. vctrl > 1.8v generates full-scale led current vctrl < 0.4v chip is off switching from 04v to 2.0v, pwm duty cycle controls the led current 5 ovp over voltage protection, 30v 6 1 vin input supply pin. bypass this pin with a capacitor as close to the device as possible
ts19371 boost (step-up) wled driver with ovp 4/10 version: g08 application information operation the ts19371 uses a constant frequency, current mode control scheme to provide excellent line and load regulation. operation can be best understood by ref erring to the block diagram. at the start of each o scillator cycle, the rs latch is set, which turns on the power switc h q1. a voltage proportional to the switch current is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the pwm comparator a2. whe n this voltage exceeds the level at the negative input of a2, the rs latch is reset turning off the power swi tch. the level at the negative input of a2 is set by the error amplif ier a1, and is simply an amplified version of the d ifference between the feedback voltage and the reference volt age of 95mv. in this manner, the error amplifier se ts the correct peak current level to keep the output in re gulation. if the error amplifiers output increases , more current is delivered to the output; if it decreases, less curr ent is delivered. soft start and current limit the internal soft start circuit minimizes the inrus h current during turning on ts19371. the typical sw itch current is limited to about 650ma by the chip. over voltage protection the ts19371 has design an internal latched off open -circuit protection circuit, the additional sense p in to detect the voltage when the leds are disconnected from the cir cuit or fail open, the ts19371 will shutdown until input condition changes to bring it out of the shutdown m ode. inductor selection a 10uh inductor is recommended for most ts19371 app lications. although small size and high efficiency are major concerns, the inductor should have low core losses at 1.2mhz and low dcr (copper wire resistance). diode selection schottky diodes, with their low forward voltage dro p and fast reverse recovery, are the ideal choices for ts19371 applications. the forward voltage drop of a schottk y diode represents the conduction losses in the dio de while the diode capacitance (ct or cd) represents the switchi ng losses. for diode selection, both forward voltag e drop and diode capacitance need to be considered. schottky d iodes with higher current ratings usually have lowe r forward voltage drop and larger diode capacitance, which ca n cause significant switching losses at the 1.2mhz switching frequency of the ts19371. a schottky diode rated at 1000ma is sufficient for most ts19371 applications . capacitor selection the small size of ceramic capacitors makes them ide al for ts19371 applications. x5r and x7r types are recommended because they retain their capacitance o ver wider voltage and temperature ranges than other types such as y5v or z5u. a 4.7f input capacitor and a 4 .7f output capacitor are sufficient for most ts193 71 applications led current control the led current is controlled by the feedback resis tor (r1). the feedback reference is 95mv. the led c urrent is 95mv/r1. the formula and table 3 for r1 selection a re shown below. r1=95mv/i led iled (ma) r1( ) 5 19.1 10 9.53 12 7.87 15 6.34 20 4.75
ts19371 boost (step-up) wled driver with ovp 5/10 version: g08 application information (continue) ts19371cx6 typical application circuit reference design information vin range (v) vled. (v) l (uh) led (series) led (parallel) current (series/ma) resistor ( ) efficiency (%) 5 19.8 22 6pcs 14 20 4.75 81.2 9 29.7 33 9pcs 14 20 4.75 83.6 12 29.7 47 9pcs 14 20 4.75 87.2 15 29.7 68 9pcs 14 20 4.75 88.4 ts19371cx6 typical application circuit for 1w x 6pc s leds reference design information vin range (v) vled. (v) l (uh) 1w led (series) current (ma) resistor ( ) efficiency (%) 12~15 19.8 68 6pcs 350 0.22 88
ts19371 boost (step-up) wled driver with ovp 6/10 version: g08 application information (continue) ts19371cs typical application circuit for 1w x 5pcs leds reference design information vin range (vac) vled. (v) l (uh) 1w led (series) current (ma) resistor ( ) efficiency (%) 12 16.5 22 5pcs 300 0.33 85 bill of material no. reference part number quantity manufacture 1 c3,c4 4.7uf/16v/ 1206 2 generic 2 d1,d2,d3,d4,d5 ss24l 5 tsc 3 d6 zd24v 1 tsc 4 l1 22uh 1 generic 5 r1 0.33 /1206 1 generic 6 u1 ts19371cs 1 tsc
ts19371 boost (step-up) wled driver with ovp 7/10 version: g08 application information (continue) led dimming control there are some different types of dimming control c ircuits: 1. using a pwm signal to shdn pin with the pwm signal applied to the shdn pin, the ts 19371 is turned on or off by the pwm signal. the le ds operate at either zero or full current. the average led current increases proportionally with the duty cycle of the pwm signal. a 0% duty cycle will turn off the ts193 71 and corresponds to zero led current. a 100% duty cycle corresponds to full current. the typical frequency range of the pwm signal is 1khz to 10khz. the magnitude of the pwm signal should be higher th an the minimum shdn voltage high. for some applications, the preferred method of brig htness control is a variable dc voltage to adjust t he led current. the dimming control using a dc voltage is shown in below figure. as the dc voltage increases, the voltage drop on r2 increases and the voltage drop on r1 dec reases. thus, the led current decreases. the select ion of r2 and r3 will make the current from the variable d c source much smaller than the led current and much larger than the fb pin bias current. for vdc range from 0v to 2v, the selection of resistors in figure 4 give s dimming control of led current from 0ma to 20ma. dimming control using a dc voltage 2. using a filtered pwm signal the filtered pwm signal can be considered as an adj ustable dc voltage. it can be used to replace the v ariable dc voltage source in dimming control. the circuit i s shown as follow: dimming control using a filtered pwm signa l 3. using control pin for dimming the pwm signal can be considered as ttl signal to c ontrol pin to change the power on/off time. vdc(v) vfb iout(ma) 2 0 0 1.8 2.2 0.43 1.6 9.2 1.8 1.4 19.6 3.6 1.2 31.1 6 1 43.4 8.5 0.8 63 12.3 0.6 74 14.5 0.4 86.4 16.9 0.2 96.9 19 0 102 20 duty iout ( ma) 0% 20 20% 17.4 30% 15 40% 12.4 50% 10 60% 8 70% 6.4 80% 4.07 100% 0 pwm : 2v ; 1khz ; vin=3.6v
ts19371 boost (step-up) wled driver with ovp 8/10 version: g08 sot-26 mechanical drawing marking diagram 71 = d evice code y = year code m = month code ( a =jan, b =feb, c =mar, d =apl, e =may, f =jun, g =jul, h =aug, i =sep, j =oct, k =nov, l =dec) l = lot code sot-26 dimension dim millimeters inches min typ max min typ max a 0.95 bsc 0.0374 bsc a1 1.9 bsc 0.0748 bsc b 2.60 2.80 3.00 0.102 0.110 0.118 c 1.40 1.50 1.70 0.055 0.059 0.066 d 2.80 2.90 3.10 0.110 0.114 0.122 e 1.00 1.10 1.20 0.039 0.043 0.047 f 0.00 -- 0.10 0.00 0.003 g 0.35 0.40 0.50 0.013 0.015 0.019 h 0.10 0.15 0.20 0.003 0.005 0.007 i 0.30 -- 0.60 0.011 -- 0.023 j 5o -- 10o 5o -- 10o
ts19371 boost (step-up) wled driver with ovp 9/10 version: g08 sop-8 mechanical drawing marking diagram y = year code m = month code ( a =jan, b =feb, c =mar, d =apl, e =may, f =jun, g =jul, h =aug, i =sep, j =oct, k =nov, l =dec) l = lot code sop-8 dimension dim millimeters inches min max min max. a 4.80 5.00 0.189 0.196 b 3.80 4.00 0.150 0.157 c 1.35 1.75 0.054 0.068 d 0.35 0.49 0.014 0.019 f 0.40 1.25 0.016 0.049 g 1.27bsc 0.05bsc k 0.10 0.25 0.004 0.009 m 0o 7o 0o 7o p 5.80 6.20 0.229 0.244 r 0.25 0.50 0.010 0.019
ts19371 boost (step-up) wled driver with ovp 10/10 version: g08 notice specifications of the products displayed herein are subject to change without notice. tsc or anyone on its behalf, assumes no responsibility or liability for any erro rs or inaccuracies. information contained herein is intended to provide a product description only. no license, express or implied, to any intellectual property rights is granted by this document. except as provided in tscs terms and co nditions of sale for such products, tsc assumes no liability wh atsoever, and disclaims any express or implied warr anty, relating to sale and/or use of tsc products includi ng liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, cop yright, or other intellectual property right. the products shown herein are not designed for use in medical, life-saving, or life-sustaining applica tions. customers using or selling these products for use i n such applications do so at their own risk and agr ee to fully indemnify tsc for any damages resulting from such i mproper use or sale.
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