ts19376 1a step-down high brightness led driver 1/8 version: a12 so t - 89 - 5l general description the ts19376 is a continuous conduction mode inducti ve step-down converter, designed for driving single or multiple series connected led efficiently from a vo ltage source higher than the total led chain voltag e. the device operates from an input supply between 8v and 32v and provides an externally adjustable output c urrent of up to 1a. depending upon the supply voltage and ext ernal components, the ts19376 can provide more than 15 watts of output power. the ts19376 includes the pow er switch and a high-side output current sensing ci rcuit, which uses an external resistor to set the nominal average output current, and a dedicated dim input a ccepts a wide range of pulsed dimming. applying a voltage of 0.3v or lower to the dim pin turns the output off and switches the device into a low current standby state features wide input voltage range: 8v to 32v up to 1a output current 5000:1 dimming single pin on/off and brightness control using pwm up to 1mhz switching frequency typical 5% output current accuracy high-side current sense hysteretic control: no compensation adjustable constant led current application white led backlighting high power led application led lighting equipment ordering information part no. package packing ts19376cy5 rmg sot-89-5l 1kpcs / 7 reel note: g denotes halogen free product. absolute maximum rating parameter symbol limit unit supply voltage v in -0.3 to 40 v driver output voltage sw -0.3 to 40 v current sense input (respect to v in ) csn +0.3 to (-6.0) v logic level dimming input dim -0.3 to +6 v switch output current i sw 1.0 a power dissipation p dmax 1.5 w operation junction temperature range t j -40 to 125 c storage temperature t stg -55 to 150 c thermal resistance from junction to case jc 15 c/w thermal resistance from junction to ambient ja 50 c/w note: ja is measured with the pcb copper area (need connect to exposed pad) of approximately 1 in 2 (multi-layer). pin definition : 1. sw 2. gnd 3. dim 4. csn 5. vin
ts19376 1a step-down high brightness led driver 2/8 version: a12 electrical specifications (v in =12v, t a =25 o c, unless otherwise noted) characteristics symbol conditions min typ max units input voltage v in 8 -- 32 v under voltage lock out v uvlo v in rising -- 7 -- v uvlo hysterisis v uvlo_hys v in falling -- 1000 -- mv max. switching frequency f sw -- -- 1 mh z current sense mean current sense threshold voltage v csn v in Cv csn 120 130 140 mv sense threshold hysteresis v csn_hys -- 15 -- % csn pin input current i csn v in Cv csn = 50mv -- 0.5 -- a dim input dim input voltage high v dim_h 2.0 -- -- v dim input voltage low v dim_l -- -- 0.3 v max. dim frequency f dim f osc = 500khz -- -- 50 kh z duty cycle range of low frequency dimming d pwm_lf f dim = 100hz 0.02% -- 1 brightness control range -- 5000:1 -- duty cycle range of high frequency dimming d pwm_hf f dim = 20khz 4% -- 1 brightness control range -- 25:1 -- dim pull up resistor to internal supply voltage r dim -- 300 -- k ? dim input leakage low i dim_l v dim = 0 -- 70 -- a output switch saturation voltage v sat i out = 0.3a -- 0.8 1.0 v saturation voltage v sat i out = 0.8a -- 1.0 1.2 v continuous sw current i swmean -- -- 1.0 a sw leakage current i leak -- 0.5 5 a thermal shutdown thermal shutdown threshold t sd -- 150 -- c thermal shutdown hysteresis t sd-hys -- 35 -- c
ts19376 1a step-down high brightness led driver 3/8 version: a12 block diagram v25 gate driver driver + - + - dim buffer vin csn dim 2.5v uvlo comparator cs comparator gnd sw 70 130mv pin function description: pin name description 1 sw switch output. sw is the output of the internal dri ver switch. 2 gnd signal and power ground. connect directly to ground plane. 3 dim logic level dimming input. drive dim low to turn of f the current regulator. drive dim high to enable the current regulator. 4 csn current sense input 5 vin input supply pin. must be locally bypassed. typical application circuit i led = a 325.0 4.0 130.0 r v s csn = =
ts19376 1a step-down high brightness led driver 4/8 version: a12 application information operation description the device, in conjunction with the coil (l1) and c urrent sense resistor (r s ), forms a self oscillating continuous- mode buck converter. when input voltage v in is first applied, the initial current in l1 and rs is zero and there is no output from the current sense circuit. under this condition, the output of cs comparator is high. this turns on an internal sw itch and switches the sw pin low, causing current to flow fr om v in to ground, via r s , l1 and the led(s). the current rises at a rate determined by v in and l1 to produce a voltage ramp (v csn ) across r s . when (v in -v csn ) > 150mv, the output of cs comparator switches low and the switch turns off. the current flowing on the r s decreases at another rate. when (v in -v csn ) < 110mv, the switch turns on again and the mean c urrent on the led is determined by ( 2 150 110 + mv) / r s = 130mv / r s . the high-side current-sensing scheme and on-board c urrent-setting circuitry minimize the number of ext ernal components while delivering led current with 5% ac curacy, using a 1% sense resistor. the ts19376 allow dimming with a pwm signal at the dim input. a logic level below 0.3v at dim forces t s19376 to turn off the led and the logic level at dim must be at least 2.0v to turn on the full led current. the frequency of pwm dimming ranges from 100hz to more than 20 khz. the dim pin is pulled high current approximately 70 a. it can be floated at normal working. when a volt age applied to dim falls below the threshold (0.3v nom.), the o utput switch is turned off. the internal regulator and voltage reference remain powered during shutdown to provide the reference for the shutdown circuit. additionally, to ensure the reliability, the ts1937 6 is built with a thermal shutdown (tsd) protection and a thermal pad. the tsd protests the ic from over temperature (150c). also the thermal pad enhances power dissip ation. as a result, the ts19376 can handle a large amount of current safely. setting nominal average output current with externa l resistor rs the nominal average output current in the led(s) is determined by the value of the external current se nse resistor (r s ) connected between v in and csn and is given by: i out = 0.130/r s (r s R RR R 0.16 ? ) this equation is valid when dim pin is float. actua lly, r s sets the maximum average current which can be adju sted to a less one by dimming. output current adjustment by pwm control a pulse width modulated (pwm) signal with duty cycl e pwm can be applied to the dim pin, as shown below , to adjust the output current to a value below the nomi nal average value set by resistor rs: i out = s r d1.0 (0 Q d Q 100%, 0.3v v pulse 2.5v) pwm dimming provides reduced brightness by modulati ng the leds forward current between 0% and 100%. t he led brightness is controlled by adjusting the relat ive ratios of the on time to the off time. a 25% br ightness level is achieved by turning the led on at full current for 25% of one cycle. to ensure this switching process between on and off state is invisible by human eyes, the switc hing frequency must be greater than 100 hz. above 1 00 hz, the human eyes average the on and off times, seeing onl y an effective brightness that is proportional to t he leds on- time duty cycle. the advantage of pwm dimming is th at the forward current is always constant; therefor e the led color does not vary with brightness as it does with analog dimming. pulsing the current provides preci se brightness control while preserving the color purity. the dimm ing frequency of ts19376 can be as high as 20 khz.
ts19376 1a step-down high brightness led driver 5/8 version: a12 application information (continue) shutdown mode taking the dim pin to a voltage below 0.3v will tur n off the output and the supply current will fall t o a low standby level of 70 a nominal. capacitor selection a low esr capacitor should be used for input decoup ling, as the esr of this capacitor appears in serie s with the supply source impedance and lowers overall efficien cy. this capacitor has to supply the relatively hig h peak current to the coil and smooth the current ripple on the in put supply. a minimum value of 4.7uf is acceptable if the input source is close to the device, but higher values wi ll improve performance at lower input voltages, esp ecially when the source impedance is high. the input capacitor s hould be placed as close as possible to the ic. for maximum stability over temperature and voltage, capacitors with x7r, x5r, or better dielectric are recommended. capacitors with y5v dielectric are not suitable for decoupling in this application and sh ould not be used. inductor selection recommended inductor values for the ts19376 are in the range 47uh to 120uh. higher values of inductance are recommended at lowe r output current in order to minimize errors due to switching delays, which result in increased ripple and lower efficiency. higher values of inductance also result in a smaller change in output current over the supply voltage ra nge. the inductor should be mounted as close to the device as possible with low resistance connections to the sw and vin pins. diode selection for maximum efficiency and performance, the rectifi er (d1) should be a fast low capacitance schottky d iode with low reverse leakage at the maximum operating voltag e and temperature. they also provide better efficie ncy than silicon diodes, due to a combination of lower forwa rd voltage and reduced recovery time. it is important to select parts with a peak current rating above the peak coil current and a continuou s current rating higher than the maximum output load current. it is very important to consider the reverse leakage of t he diode when operating above 85c. excess leakage will incr ease the power dissipation in the device and if clo se to the load may create a thermal runaway condition. the higher forward voltage and overshoot due to rev erse recovery time in silicon diodes will increase the peak voltage on the sw output. if a silicon diode is use d, care should be taken to ensure that the total vo ltage appearing on the sw pin including supply ripple, does not exc eed the specified maximum value. reducing output ripple peak to peak ripple current in the led(s) can be re duced, if required, by shunting a capacitor cled ac ross the led(s) as shown below: a value of 1uf will reduce the supply ripple curren t by a factor three (approx.). proportionally lower ripple can be achieved with higher capacitor values. note that th e capacitor will not affect operating frequency or efficiency, but it will increase start-up delay and reduce the frequen cy of dimming, by reducing the rate of rise of led voltage. by adding this capacitor the current waveform throu gh the led(s) changes from a triangular ramp to a m ore sinusoidal version without altering the mean curren t value.
ts19376 1a step-down high brightness led driver 6/8 version: a12 application information (continue) operation at low supply voltage the internal regulator disables the drive to the sw itch until the supply has risen above the startup t hreshold (vuvlo). above this threshold, the device will star t to for this reason, the temperature coefficients of the operating. however, with the supply voltage below the specifie d minimum value, the switch duty cycle will be high and the device power dissipation will be at a maximum. care should be taken to avoid operating the device unde r such conditions in the application, in order to minimize the risk of exceeding the maximum allowed die temp erature. (see next section on thermal considerations). the drive to the switch is turned off when the supply voltage falls below the under-voltage threshold (vuvlo-1v). this prevents the switch working with excessive 'on ' resistance under conditions where the duty cycle is high. thermal shutdown protection to ensure the reliability, the ts19376 is built wit h a thermal shutdown (tsd) protection function. the tsd protests the ic from over temperature (150c). when the chip temperature decreases (115c), the ic recovers aga in.
ts19376 1a step-down high brightness led driver 7/8 version: a12 sot-89-5l mechanical drawing sot-89-5l dimension dim millimeters inches min max min max a 4.40 4.60 0.17 0.18 b 4.05 4.25 0.16 0.17 c 1.50 1.70 0.06 0.07 d 0.35 0.41 0.01 0.02 e 2.40 2.60 0.09 0.10 f 0.80 -- 0.03 -- g 3.00(typ) 0.12(typ) h 1.50(typ) 0.06(typ) i 0.40 0.52 0.01 0.02 j 1.40 1.60 0.05 0.06
ts19376 1a step-down high brightness led driver 8/8 version: a12 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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