ts 19450 ac/dc wled driver with external mosfet universal high brightness 1 / 8 version: a10 sop - 8 general description the ts 19450 is an open loop, current mode control led driver ic. it can be programmed to operate in either a constant frequency or constant off - time mode. it includes an 8v~450v linear regulator which allows it to wo rk from a wide range of input voltages without the need for an external low voltage supply. the TS19450 includes a pwm dimming input that can accept an external control signal with a duty ratio of 0~100% and a frequency of up to a few khz. it also includes a 0~250mv linear dimming input which can be used for linear dimming of the led current. the TS19450 is ideally suited for buck led drivers. since it operates in open loop current mode control, the controller achieves good output current regulation without the need for any loop compensation. pwm dimming response is limited only by the rate of rise and fall of the inductor current, enabling very fast rise and fall times. the TS19450 requires only free external components (apart from the power stage) to produ ce a controlled led current making it and ideal solution for low cost led drivers. ordering information part no. package packing ts 19450cs rl sop - 8 2.5kpcs / 13 reel features switch mode controller for single switch led drivers open loop peak current controller internal 8v~450v linear regulator constant frequency or constant off - time op eration linear and pwm dimming capability requires few external components for operation application dc/dc or ac/dc led driver applicat ions rgb backlighting led driver back lighting of flat panel displays general purpose constant current source signage and decorative led lighting charger typical application circuit absolute maximum rating parameter symbol limit unit input voltage range v in to gnd - 0.5 ~ +470 v internal regulated voltage v dd to gnd 13.5 v cs, ld, pwmd, gate, rt to gnd - 0.3 ~ ( v dd +0.3) v continuous power dissipation p d 630 mw storage temperature range t a - 65 to +150 o c junction temperature range t j - 40 to +150 o c thermal resistance junction to ambient r ja 128 o c /w pin definition : 1. vin 8. rt 2. cs 7. ld 3. gnd 6. vdd 4. gate 5. pwmd
ts 19450 ac/dc wled driver with external mosfet universal high brightness 2 / 8 version: a10 electrical specifications ( t a = 25 o c , v in = 12v, unless otherwise noted ) function parameter symbol test conditions min typ max units input dc input voltage range v in dc dc input voltage 8.0 -- 450 v shut - down mode suppl y current i insd pin pwmd to gnd -- 0.5 1 .0 ma internal regulator internally regulated voltage v dd v in =8v, i dd(ext) =0, 500pf at gate, r t =226k , pwmd=v dd 7.0 7. 5 8.0 v line regulation of v dd ?v ddline v in =8~450v, i dd(ext) =0, 500pf at gate, r t =226k , pwmd=v dd 0 -- 1.0 v load regulation of v dd ?v ddload i dd(ext) =0~1ma, 500pf at gate, r t =226k , pwmd=v dd 0 -- 100 mv undervoltage lockout threshold uvlo v dd rising 6.45 6.7 6.95 v undervoltage lockout hysteresis ? uvlo v dd falling -- 500 -- mv vdd current availa ble for external circuitry v dd (ext) v in =8v~100v -- -- 1.0 ma dimming pwmd input low voltage v enl v in =8v~450v -- -- 1.0 v pwmd input high voltage v enh v in =8v~450v 2.4 -- -- v pwmd pull - down resistance at pwmd r en v pwmd =5v 50 100 150 k linear dimming pin voltage v ld v in =12v 0 -- 250 mv current sense comparator - 40 c < t a < +85 c 225 250 275 current sense pull - in threshold voltage v csth t a < +125 c 213 250 287 mv offset voltage for ld comparator v offset - 12 -- 12 mv current sense blanking inter val t blank v ld =v dd , v c s =0.55v ld 150 215 280 ns delay to output t delay v in =12v, v ld =0.15v, v cs =0~0.22v after t blank -- -- 300 ns oscillator r t =1m 20 25 30 oscillator frequency f osc r t =223k 80 100 120 khz max. oscillator pwm duty cycle d max f=25khz at gate, cs to gnd -- -- 100 % gate driver gate sourcing current i source v gate =0v, v dd =7.5v 165 -- -- ma gate sinking current i sink v gate =v dd , v dd =7.5v 165 -- -- ma gat e high output voltage v gate(hi) i out = - 10ma v dd - 0.3 -- v dd v gate low output voltage v gate(lo) i out =10ma 0 -- 0.3 v gate output rise time t rise c gate =500pf, 10%~90% v gate -- 30 50 ns gate output fall time t fall c gate =500pf, 90%~10% v gate -- 30 50 ns no te 1 : limited by package power dissipation, whichever is lower note 2 : v dd load current external to the TS19450 note 3 : denotes the specifications which apply over the full operating ambient temperature range of - 40 c ts 19450 ac/dc wled driver with external mosfet universal high brightness 3 / 8 version: a10 block diagram pin descr iption pin function description 1 vin this pin is the input of 8v~450v linear regulator 2 cs this pin is the current sense pin used to sense the mosfet current by means of an external sense resistor. when this pin exceeds the low of either the internal 2 50mv or the voltage at the ld pin, the gate output goes low 3 gnd ground return for all internal circuitry. this pin must be electrically connected to the ground of the power train. 4 gate this pin is the output gate driver for an external n - ch power mos fet 5 pwmd this is the pwm dimming input of the ic. when this pin is pulled to gnd, the gate driver is turned off. when the pin is pulled high, the gate driver operates normally. 6 vdd this is the power supply pin for all internal circuits. it must be by passed with a low esr capacitor to gnd ( 0.1 f) 7 ld this pin is the linear dimming input and sets the current sense threshold as long as the voltage at the pin is less than 250mv (typ.) 8 rt this pin sets the oscillator frequency. when a resistor is con nected between rt and gnd, the ic operates in constant frequency mode. when the resistor is connected between rt and gate, the ic operates in constant off - time mode.
ts 19450 ac/dc wled driver with external mosfet universal high brightness 4 / 8 version: a10 application information the TS19450 is optimized to drive buck led drivers using op en - loop peak current mode control. this method of control enables fairly accurate led current control without the need for high side current sensing or the design of any closed loop controllers. the ic uses very few external components and enables both lin ear and pwm dimming of the led current. a resistor connected to the rt pin programs the frequency of operation (or the off - time). the oscillator produces pulses at regular intervals. these pulses set the sr ip - ?p in the TS19450 which causes the gate driv er to turn on. the same pulses also start the blanking timer which inhibits the reset input of the sr ip op and prevent false turn - offs due to the turn - on spike. when the fet turns on, the current through the inductor starts ramping up. this current ?ws through the external sense resistor r cs and produces a ramp voltage at the cs pin. the comparators are constantly comparing the cs pin voltage to both the voltage at the ld pin and the internal 250mv. once the blanking timer is complete, the output of the se comparators is allowed to reset the ?p ?p. when the output of either one of the two comparators goes high, the ip op is reset and the gate output goes low. the gate goes low until the sr ip ?p is set by the oscillator. assuming a 30% ripple in the inductor, the current sense resistor r cs can be set using: constant frequency peak current mode control has an in herent disadvantage at duty cycles greater than 0.5, the control scheme goes into sub harmonic oscillations. to pre vent this, an arti c ial slope is typically added to the current sense waveform. this slope compensation scheme will af fect the accuracy of the led current in the present form. however, a constant off - time peak current control scheme does not have this problem and can easily operate at duty cycles greater then 0.5 and also gives inherent input volt age rejection making the led current almost insensitive to input voltage variations. but, it leads to variable frequency operation and the frequency range depends greatly on the inp ut and output voltage variation. TS19450 makes it easy to switch between the two modes of operation by changing one connection (see oscillator section). input voltage regulator the TS19450 can be powered directly from its vin pin and can work from 8.0v~45 0vdc at its vin pin. when a voltage is applied at the vin pin, the TS19450 maintains a constant 7.5v at the vdd pin. this voltage is used to power the ic and any external resistor dividers needed to control the ic. the vdd pin must be bypassed by a low esr capacitor to provide a low impedance path for the high frequency current of the output gate driver. the TS19450 can be also operated by supplying a voltage at the vdd pin greater than the internally regulated voltage. this will turn off the internal line ar regulator of the ic and the TS19450 will operate directly off the voltage supplied at the vdd pin. please note that this external voltage at the vdd pin should not exceed 12v. " m u i p v h i u i f 7 * / q j o p g u i f 5 4 j t s b u f e v q u p 7
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ts 19450 ac/dc wled driver with external mosfet universal high brightness 5 / 8 version: a10 applicat ion information (continue) 5 i f j o q v u d v s s f o u e s b x o g s p n u i f 7 * / q j o j t b t v n p g u i f n " d v s s f o u e s b x o c z u i f j o u f s o b m d j s d v j u b o e u i f d v s s f o u e s b x o c z u i f ( " 5 & e s j w f s x i j d i j o u v s o e f q f o e t p o u i f t x j u d i j o h g s f r v f o d z b o e u i f ( " 5 & d i b s h f p g u i f f y u f s o b m * o u i f b c p w f f r v b u j p o
g 4 j t u i f t x j u d i j o h g s f r v f o d z b o e 2 ( j t u i f ( " 5 & d i b s h f p g u i f f y u f s o b m . 0 4 ' & 5 x i j d i d b o c f p c u b j o f e g s p n u i f e b u b t i f f u p g u i f . 0 4 ' & 5
current sense the current sense input of the TS19450 goes to the non - inverting inputs of two comparators. the inverting terminal of one comparator is tied to an internal 250mv reference whereas the inverting terminal of the other comparator is connected to the ld pin. the outputs of both these com parators are fed into an or gate and the output o f the or gate is fed into the reset pin of the ip - ?p. thus, the com parator which has the lowest voltage at the inverting terminal determines when the gate output is turned off. the outputs of the comparators also include a 150~280ns blanking time which prevents spurious turn - offs of the exter - nal mosfet due to the turn - on spike normally present in peak current mode control. in rare cases, this internal blanking might not be enough to lter out the turn - on spike. in these cases, an external rc lter need s to be added between the external sense resistor (r cs ) and the cs pin. please note that the comparators are fast (with a typical 80ns response time). hence these comparators are more susceptible to be triggered by noise than the comparators of the ts1945 0. a proper layout minimizing external induc - tances will prevent false triggering of these comparators. oscillator the oscillator in the TS19450 is controlled by a single re sistor connected at the rt pin. the equation governing the oscillator time period t osc is given by: if the resistor is connected between rt and gnd, TS19450 operates in a constant frequency mode and the above equa tion determines the time - period. if the resistor is connected between rt and gate, the TS19450 operates in a constant of f - time mode and the above equation determines the off - time. linear dimming the linear dimming pin is used to control the led current. there are two cases when it may be necessary to use the linear dimming pin. * i n some cases, it may not be possible to nd the exact value required to obtain the led current when the r cs internal 250mv is used. in these cases, an external volt age divider from the vdd pin can be connected to the ld pin to obtain a voltage (less than 250mv) corresponding to the desired voltage across r cs . * linear dimming may be desired to adjust the current level to reduce the intensity of the leds. in these cases, an external 0~250mv voltage can be connected to the ld pin to adjust the led curr ent during operation. to use the internal 250mv, the ld pin can be connected to vdd. note: although the ld pin can be pulled to gnd, the output cur rent will not go to zero. this is due to the presence of a mini - mum on - time (which is equal to the sum of the blanking time and the delay to output time) which is about 450ns. this will cause the mos fet to be on for a minimum of 450ns and thus the led current when ld = gnd will not be zero. this current is also dependent on the input voltage, inductance value , for ward voltage of the leds and circuit parasitic. to get zero led current, the pwmd pin has to be used.
ts 19450 ac/dc wled driver with external mosfet universal high brightness 6 / 8 version: a10 application information (continue) pwm dimming pwm dimming can be achieved by driving the pwmd pin with a low frequency square wave signal. when th e pwm signal is zero, the gate driver is turned off and when the pwmd signal if high, the gate driver is enabled. since the pwmd signal does not turn off the other parts of the ic, the response of the TS19450 to the pwmd signal is almost instantaneous. the rate of rise and fall of the led current is thus determined solely by the rise and fall times of the induc tor current. to disable pwm dimming and enable the TS19450 permanently, connect the pwmd pin to vdd
ts 19450 ac/dc wled driver with external mosfet universal high brightness 7 / 8 version: a10 sop - 8 mechan ical 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 millimeters inches dim 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 0 7 0 7 p 5.80 6.20 0.229 0.244 r 0.25 0.50 0.010 0.019
ts 19450 ac/dc wled driver with external mosfet universal high brightness 8 / 8 version: a10 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 e rrors 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 tsc? terms and conditions of sal e for such products, tsc assumes no liability whatsoever, and disclaims any express or implied warranty, relating to sale and/or use of tsc products including liability or warranties relating to fitness for a particular purpose, merchantability, or infring ement of any patent, copyright, or other intellectual property right. the products shown herein are not designed for use in medical, life - saving, or life - sustaining applications. customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify tsc for any damages resulting from such improper use or sale.
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