TS19378 2a buck (step-down) wled driver 1/7 version: a13 so p - 8 ep general description the TS19378 is a high voltage step-down converter d esigned for driving up to 10 series white leds from a 40v system input. the total led driving current up to 2 a, which is measured through an external current se nse resistor. its low 200mv feedback voltage reduces po wer loss and improves efficiency. the ovp pin monit ors the output voltage and turns off the converter if an ov er-voltage condition is present due to an open circ uit condition. the TS19378 includes current limit, short circuit p rotection and thermal shutdown protection preventin g damage. TS19378 provides high power, high efficiency, and e xcellent transient characteristics. the pwm control circuit is able to the duty ratio linearly from 0 up to 100%. since this converter can accommodate an input volta ge up to 40v, it is also suitable for the operation via an a c adapter . features input voltage range 8v~40v output voltage up to 38v 2a switch output current duty ratio: 0%~100% pwm control 300khz switching frequency enable/disable functions soft start time control current limit and thermal shutdown short circuit protections built-in internal sw p-ch mos application white led backlighting high power led application multiple led driving led lighting equipment ordering information part no. package packing TS19378cs rlg sop-8ep 2.5kpcs / 13 reel note: g denotes halogen free product. block diagram pin definition : 1. en/ss 8. comp 2. gnd 7. fb 3. vgate 6. ovp 4. vcc 5. sw
TS19378 2a buck (step-down) wled driver 2/7 version: a13 absolute maximum rating parameter symbol limit unit v cc pin voltage v cc v ss - 0.3 to v ss + 45 v feedback pin voltage v fb v ss - 0.3 to 6 v en/ss pin voltage v en/ss v ss - 0.3 to 6 v ovp pin voltage v ovp v ss - 0.3 to v cc v comp pin voltage v comp v ss - 0.3 to 6 v vgate pin voltage v gate v ss - 0.3 to v cc v switch pin voltage v sw v ss - 0.3 to v cc + 0.3 v power dissipation pd internally limited mw storage temperature range t st -65 to +150 c operating junction temperature range t ojp -40 to +125 c operating supply voltage v op 8 to 40 v output voltage v out 38 v thermal resistance from junction to case jc 15 c/w thermal resistance from junction to ambient ja 40 c/w note: ja is measured with the pcb copper area(need connect to exposed pad) of approximately 1.5 in 2 (multi-layer). electrical specifications (v in =12v, t a =25 o c, unless otherwise noted) parameter symbol conditions min typ max units feedback voltage v fb i out =0.2a 0.19 0.20 0.21 v quiescent current i ccq v fb =0.5v force driver off -- 3 6 ma feedback bias current i fb i out =0.1a -- 0.1 0.5 ua shutdown supply current i sd v en =0v -- 150 300 ua switch current limit i swlimit 2.5 -- -- a oscillation frequency f osc 240 300 360 khz short frequency f osc -- 50 -- khz en/ss pin shutdown logic input threshold voltage v sl low (regulator off) -- -- 0.8 v en/ss pin input current i en/ss v en =0v -- 5 -- ua internal mosfet r dson r dson v cc =5v, v fb =0v -- 130 180 m ? ovp sense voltage v ovp 0.833 0.850 0.867 v thermal shutdown temp t sd -- 150 -- c thermal shutdown hysteresis t sh -- 40 -- c
TS19378 2a buck (step-down) wled driver 3/7 version: a13 typical application circuit a: normal application circuit c1 33uh l1 r5 0.6 vin d1 b340 c5 0.1uf ovp 4 3 vgate 1 vcc 8 vss 2 comp 7 fb 6 sw 5 ax2005/a c6 0.1uf c2 0.1uf r1 c3 1uf r4 r3 8.2k led-1 220uf en/ss u1 i led r2 c7 15n 100 d2 diode dimming 100hz-50khz c4 470uf led-n vout vfb = 0.2v i led = v fb /r5 v ovp (ovp) = 0.85 (1+ ) r4 r1 20k c out esr range r2 c7 30~80m ? 470r 10nf 80~300m ? 100r 15nf b: ac input application circuit 9inverting) c1 33uh l1 r5 0.6 d1 b340 c5 0.1uf ovp 4 3 vgate 1 vcc 8 vss 2 comp 7 fb 6 sw 5 ax2005/a c6 0.1uf c2 0.1uf r1 c3 1uf r4 r3 8.2k led-1 220uf en/ss u1 r2 c7 33nf 560 ac adapter vout led-2 led-3 led-4 i led bridge rectifier vfb = 0.2v i led = v fb /r5 v ovp (ovp) = 0.85 (1+ ) r4 r1 20k c4 100uf i led r5 c1 l1 350ma 0.57 ? 70mw 100uf 33uh 750ma 0.266 ? 150mw 220uf 1000ma 0.2 ? 200mw 330uf
TS19378 2a buck (step-down) wled driver 4/7 version: a13 function descriptions pwm control the TS19378 consists of dc/dc converters that emplo y a pulse-width modulation (pwm) system. in convert ers of the TS19378, the pulse width varies in a range from 0 to 100%, according to the load current. the ripp le voltage produced by the switching can easily be removed thr ough a filter because the switching frequency remai ns constant. therefore, these converters provide a low -ripple power over broad ranges of input voltage an d load current setting i led current application circuit item shows the basic applicatio n circuit with TS19378 adjustable output version. t he external resistor sets the led output current according to t he following formula: i led =(0.25v/r5), v fb =0.2v resistor select for led output current setting i led r2 350ma 0.57 ? 70mw 750ma 0.266 ? 150mw 1000ma 0.2 ? 200mw current liming the current limit threshold is setting by the inter nal circuit. compensation in all led driver applications. connecting a resist or (r2) and a capacitor (c7) from comp pin to gnd. please refer the application circuit table to design. en/ss this pin can be supplied shutdown or soft start fun ction. it is inside pull high function. for normal application, the pin must be connected a capacitor to ground. there is a 5ua current to charge this capacitor, vary the different capacitor value to control soft start time. allow t he switching regulator circuit to be shutdown pulli ng this pin below a 0.8v threshold voltage; the shutdown supply curre nt is approximately 150ua inductor selection for most designs, the different frequency can be re ducing the inductor value; the TS19378 is suggested 33uh. where is inductor ripple current. large value induc tors lower ripple current and small value inductors result in high ripple currents. choose inductor ripple current app roximately 20% of the maximum load current 2a, ? il=0.4a. the dc current rating of the inductor should be at leas t equal to the maximum load current plus half the r ipple current to prevent core saturation (2a+0.2a). input capacitor selection this capacitor should be located close to the ic us ing short leads and the voltage rating should be ap proximately 1.5 times the maximum input voltage. the rms curren t rating requirement for the input capacitor of a b uck regulator is approximately 1M2 the dc load current. a l ow esr input capacitor sized for maximum rm s current must be used. a 220f low esr capacitor for most ap plications is sufficient. over voltage protection the ovp voltage is set by outside resistance (r1 an d r4). the external resistor sets the ovp voltage a ccording to the following equation: ) 1r 4r 1( v ) ovp ( v ovp out + = if v ovp >0.85v, the ovp is happened that to disable the dr iver until v ovp <0.85v.
TS19378 2a buck (step-down) wled driver 5/7 version: a13 function descriptions (continue) output capacitor selection for lower output voltage ripple and more stable led current, higher value output capacitor and low esr is recommended. a 470uf electrolytic capacitor works f or most of the applications.
TS19378 2a buck (step-down) wled driver 6/7 version: a13 sop-8ep mechanical drawing marking diagram y = year code m = month code for halogen free product ( o =jan, p =feb, q =mar, r =apl, s =may, t =jun, u =jul, v =aug, w =sep, x =oct, y =nov, z =dec) l = lot code sop-8ep 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 e 2.05 2.41 0.081 0.095 e1 2.82 3.30 0.111 0.130 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
TS19378 2a buck (step-down) wled driver 7/7 version: a13 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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