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preliminary TTP933 2013/08/23 page j 1?25 ver. j 1.2 1.5a led driver with internal switch
preliminary TTP933 2013/08/23 page j 2?25 ver. j 1.2 . general description TTP933 is a high efficiency , constant current , c ontinuous mode inductive step-down converter, designed for driving constant current to high power (single or multiple) led with only 4 external components. TTP933 operates from input supply betw een 5v and 33v and provides an externally adjustable output current of up to 1.5a. the TTP933 is specifically designed with pfm control to enhance the efficiency up to 97%. the output current can be modify by an external resister , and can adjusted , by a pplying an external control signal to the dim pin , the dim pin will accept a pwm waveform. additionally, to ensure the system reliability , TTP933 is built-in with over temperature protection, and led open-circuit short-circuit protecti on to protect system from being damaged. . features ? 1.5a output current ? wide input voltage range: 5v to 33v ? high efficiency (up to 97%) ? internal ndmos power switch ? single pin on/off and brightness control using pwm ? hysteretic pfm improves e fficiency at light loads ? with thermal/soft start /led open-short detect protection ? only 4 external components ? up to 1mhz switching frequency ? typical 3% output current accuracy . applications z high power led lighting z automotive led lighting z low voltage industrial lighting z led back-up lighting z constant current source
preliminary TTP933 2013/08/23 page j 3?25 ver. j 1.2 . package type TTP933-jo8 dim en 5 gnd gnd TTP933-fa6 sot23-6 6 sen sw vin 4 dim 3 2 1 TTP933-gg5 vin sen gnd dim 5 sw 1 sot89-5 4 3 2 to-252 TTP933-he5 vin sen gnd dim 5 4 3 2 1 sw sop-8 gnd dgnd sw sw sen vin 8 7 6 5 4 3 2 1 sop-8 gnd dgnd sw sw en dim sen vin TTP933-do8 8 7 6 5 4 3 2 1 dgnd gnd sop-8 TTP933-co8 8 7 6 5 sw dim sen 4 3 2 1 vin 5 gnd sen sw vin 4 TTP933-ea5 sot23-5 dim 3 2 1 dgnd gnd msop-8 TTP933-bm8 8 7 6 5 sw dim sen 4 3 2 1 vin 551#..401 xjui5ifsnbm1be
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. pin description pin name pin description sw drain of ndmos switch gnd ground pad dgnd source of ndmos dim dimming control pad sen i sense connect resistor rs from this pin to vin to define nominal average output current vin power pad en enable control signal, h:active , l:power down, built-in pull high
preliminary TTP933 2013/08/23 page j 4?25 ver. j 1.2 .application circuit rs d1 l1 68uh 10uf/50v cled sw v in dim gnd i sense TTP933 c1 gnd 10uf/50v typical applicatiom circuit vin .absolute maximum ratings item symbol rating unit supply voltage v in 0-33 (40v for 0.5 sec) v output current i out 1.8 a sustaining voltage at sw pin v sw -0.5~33 (40v for 0.5 sec) v power dissipation * sop8 p d 1.4 w msop8(thermal pad) 1.45 to252 2.8 sot23-6 1.2 sot23-5 1.2 sot89-5 1.45 thermal resistance sop8 rth(j-a) 89.3
/w msop8(thermal pad) 86.2 to252 44.6 sot23-6 104.2 sot23-5 104.2 sot89-5 86.2 operating temperature top -40
- +85

storage temperature tsto -55
- +150

junction temperature tj- max 150
* 2 layer the pcb size is 22mm*20mm ** power dissipation depend on pcb layout. dgnd en
preliminary TTP933 2013/08/23 page j 5?25 ver. j 1.2 . electrical characteristics test condition : v in= 12v, v out = 3.6v, l1=68uh, c in= c out = 10uf , ta= 25
; unless otherwise specified. item symbol condition min g typ g max g unit operating voltage v in 5 - 33 v operating current i in v in= 5v~33v - 1 2 ma power down current i off v in= 5v~33v, en pin grounded 50 ua output current i out - - 1.5 a output current accuracy i out / i out 150ma i out " ? 3 ? 5 % efficiency v in= 12v, i out = 350ma,v ou t =10.8v 97 % sw dropout voltage vsw i out =1a 0.5 v internal propagation delay t pd 100 200 300 ns input voltage v ih 3.5 5 v v il 0.5 v sense threshold hysteresis v sensehys ? 15 - % mean current sense threshold voltage v sense 95 100 105 mv switch on resistance r ds(on) 7 */ 7 * 065 n" 7 pvu 7 0.33 ? minimum switch ?on? time t onmin 100 350 450 ns minimum switch ?off? time t offmin 100 350 450 ns recommended duty cycle range oft switch dsw 0.2 0.8 maximum operating frequency freq max 40 1000 k h z thermal shutdown threshold t sd 145 160 175
thermal shutdown hystersis t sd-hys 20
duty cycle range of pwm signal applied to dim pin duty dim pwm frequency = 1khz 0.01 1 rise time of output current tr v out= 3.6v , i out = 350ma, f dim =1khz , duty dim =50% 20 ns fall time of output current tf v out= 3.6v , i out = 350ma, f dim =1khz , duty dim =50% 20 ns
preliminary TTP933 2013/08/23 page j 6?25 ver. j 1.2 .block diagram device description the device, in conjunction with th e coil (l1) and current sense resi stor (rs), forms a selfoscillating continuous-mode buck converter. device operation (refer to block diagram and fi gure 1 - operating waveforms) operation can be best understood by assuming that the dim pin of the de vice is unconnected and the voltage on this pin (vdim) appears dire ctly at the (+) input of the comparator. when input voltage vin is first applied, the initia l current in l1 and rs is zero and there is no output from the current sense circ uit. under this condition, the (-) i nput to the comparator is at ground and its output is high. this turns mn on and switches the sw pin low, causing current to flow from vin to ground, via rs, l1 and the led(s) . the current rises at a rate determined by vin and l1 to produce a voltage ramp (vsense) acro ss rs. the supply referred voltage vsense is forced across internal resistor r1 by the current sense circuit a nd produces a proportional current in internal resistors r2 and r3. this produces a ground referred rising voltage at the (-) input of the comparator. when this reaches the threshol d voltage (vref), the co mparator output switches low and mn turns off. the comparator output also drives another nmos switch, which bypasses internal resistor r3 to provide a controlled amount of hysteresis. the hysteresis is set by r3 to be nominally 15% of vadj. when mn is off, the current in l1 continues to fl ow via d1 and the led(s) back to vin. the current decays at a rate determined by the led(s) and diode forward voltages to produce a falling voltage at the input of the comparator. wh en this voltage returns to vadj, the comparator output switches high again. this cycle of events repeats, with the comparator input ramping between limits of vref 15%. dgnd en
preliminary TTP933 2013/08/23 page j 7?25 ver. j 1.2 switching thresholds with vadj = vref, the ratios of r1, r2 and r3 define an average vsense switching threshold of 100mv (measured on the isense pin with respect to vin). the average output current ioutnom is then defined by this voltage and rs according to: ioutnom = 100mv/rs nominal ripple current is 15mv/rs
preliminary TTP933 2013/08/23 page j 8?25 ver. j 1.2 . typical performance characteristics 1. efficiency vs. input voltage at various led cascaded number efficiency vs. input voltage @l=22uh, i out =384ma efficiency vs. input voltage @l=68uh, i out =384ma efficiency vs. input voltage @l=22uh, i out =769ma
preliminary TTP933 2013/08/23 page j 9?25 ver. j 1.2 efficiency vs. input voltage @l=68uh, i out =769ma efficiency vs. input voltage @l=22uh, i out =1000ma efficiency vs. input voltage @l=68uh, i out =1000ma
preliminary TTP933 2013/08/23 page j 10?25 ver. j 1.2 2. efficiency vs. led cascaded num ber at various input voltage efficiency vs. led cascaded number @l=22uh, i out =384ma efficiency vs. led cascaded number @l=68uh, i out =384ma efficiency vs. led cascaded number @l=22uh, i out =769ma
preliminary TTP933 2013/08/23 page j 11?25 ver. j 1.2 efficiency vs. led cascaded number @l=68uh, i out =769ma efficiency vs. led cascaded number @l=22uh, i out =1000ma efficiency vs. led cascaded number @l=68uh, i out =1000ma
preliminary TTP933 2013/08/23 page j 12?25 ver. j 1.2 3. output current vs. input volt age at various led cascaded number output current vs. input voltage @l=22uh, i out =384ma output current vs. input voltage @l=68uh, i out =384ma output current vs. input voltage @l=22uh, i out =769ma
preliminary TTP933 2013/08/23 page j 13?25 ver. j 1.2 output current vs. input voltage @l=68uh, i out =769ma output current vs. input voltage @l=22uh, i out =1000ma output current vs. input voltage @l=68uh, i out =1000ma
preliminary TTP933 2013/08/23 page j 14?25 ver. j 1.2 4. output currnet vs. input voltage at various inductor output current vs. input vo ltage @1-led in cascaded, i out =384ma output current vs. input vo ltage @2-led in cascaded, i out =384ma output current vs. input vo ltage @3-led in cascaded, i out =384ma
preliminary TTP933 2013/08/23 page j 15?25 ver. j 1.2 5. output current vs. led cascaded number at various input voltage output current vs. led cascaded number @l=22uh, i out =384ma output current vs. led cascaded number @l=68uh, i out =384ma output current vs. led cascaded number @l=22uh, i out =769ma
preliminary TTP933 2013/08/23 page j 16?25 ver. j 1.2 output current vs. led cascaded number @l=68uh, i out =769ma 6. output current vs. led casc aded number at various inductor output current vs. led cascaded number @vin=12v, i out =384ma output current vs. led cascaded number @vin=24v, i out =384ma
preliminary TTP933 2013/08/23 page j 17?25 ver. j 1.2 7. switching frequency vs. led casc aded number at various inductor switching frequency vs. led cascaded number @vin=12v, i out =384ma switching frequency vs. led cascaded number @vin=24v, i out =384ma switching frequency vs. led cascaded number @vin=30v, i out =384ma
preliminary TTP933 2013/08/23 page j 18?25 ver. j 1.2 8. dimming and swit ching waveforms v dim v sw i out dimming waveform(v in =12v, r sen =0.27 ? , 3-led) v sw i l switching waveform(v in =12v, r sen =0.27 ? , 3-led)
preliminary TTP933 2013/08/23 page j 19?25 ver. j 1.2 . application notes .setting nominal average output curr ent with external resistor rs the nominal average output current in the led(s) is determined by the value of the external current sense resistor (rs) connected betw een vin and iout and is given by: ioutnom = 0.1/r s [for r s 0.1 ? ] nominal ripple current is 15mv/r s the table below gives values of nominal average output current for several preferred values of current setting resistor (rs) in the typi cal application circu it shown on page 1: rs( ? ) nominal average output current (ma) 0.1 1000 0.13 760 0.15 667 . dimming a pulse width modulated (pwm) signal with duty cy cle dpwm can be applied to the dim pin ., a logic low ( below 0.5v) at dim will disable the internal mosfet and turn off the current flow to the led array . an internal pull-high circuit en sures that the TTP933 is on when dim pin is unconnected . . open / short circuit led protection when any led is open - circuit , the output current will be turned off . when any led is short - circuit , the output current will be limited to its preset value . . over temperature protection when the junction temperature over range . TTP933 will turn off output current . .minimum input voltage the minimum input voltage is the sum of the voltage drops on r sen , dcr of l1 , rds (on) of internal mos switch and the to tal forward voltage of leds v led . vin=v rs +v led +v l1 +v sw . .design consideration : .switching frequency for better output current accuracy , the switching frequency should be determined by minimum on/off time sw waveform . f sw =(1-d)/t off,min , when the duty cycle is large than 0.5 (d = vout / vin) or f sw =d/t on,,min , when the duty cycle is smaller than 0.5
preliminary TTP933 2013/08/23 page j 20?25 ver. j 1.2 the switching frequency is related to effici ency ( better at low frequency) , the size/cost of components , and the amplitude of output ripple voltage and current ( smaller at high frequency) . the slower switching frequency comes from the large value of inductor . in many applications , the sensitivity of emi limits the switching frequency . the switching frequency can be ranged from 40khz to 1.0mhz . . led ripple current a led constant current driver , is designed to control the current through the cascaded led , instead of the voltage across it . hi gher led ripple current allo ws the use of smaller inductance , smaller output capacitan ce and even without an output cap acitor . the advantages of higher led ripple current are to minimize pcb size and redu ce cost because of no output capacitor . lower led ripple current requires large induce and out put capacitor . the advantages of lower led ripple current are to extend led life time and to reduce heating of led . the recommended ripple current is from 5 % to 20% of normal led output current . capacitor selection a low esr capacitor should be used for input decoupling, as the es r of this capacitor appears in series with the supply source impedance and lowe rs overall efficiency. this capacitor has to supply the relatively high peak current to th e coil and smooth the current ripple on the input supply. a minimum value of 4.7uf is acceptable if the input source is close to the device, but higher values will improve performance at lower input voltages, especially when the source impedance is high. the input capacitor should be placed as close as possible to the ic. for maximum stability over temperature and vo ltage, capacitors with x7r, x5r, or better dielectric are recommended. capacitors with y5v di electric are not suitable for decoupling in this application and should not be used . a suitable murata cap acitor would be grm42-2x7r475k-50. inductor selection the inductance is determined by two factors : the switching frequency and the inductor ripple current. the calculation of the inductance , l1 , can be described as l1>(v in -v out -v sen -(rds (on)x i out ))x d/( f sw x i l ) higher values of inductance ar e recommended at higher supply voltages 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 range. (see graphs). the inductor should be mounte d as close to the device as possible with low resistance connections to the sw and v in pins. the chosen coil should have a saturation current higher than th e peak output current and a continuous current rating above th e required mean output current. the inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times within the specified limits over the supply voltage and lo ad current range. switch on time ton= l ? i/(v in -v led ? i avg (r s + rl + rsw ) ) t off = l ? i/(v led + v d + i avg ( r s + rl) )
preliminary TTP933 2013/08/23 page j 21?25 ver. j 1.2 where l is the coil inductance rl is the coil resistance r s is the current sense resistance iavg is the required led current ? i is the coil peak-peak ripple current {inter nally set to 0.3 x iavg} v in is the supply voltage v led is the total led forward voltage r sw is the switch resistance v d is the diode forward voltage at the required load current diode selection : for maximum efficiency and performance, the r ectifier (d1) should be a fast low capacitance schottky diode with low reverse leakage at th e maximum operating voltage and temperature. they also provide better efficiency than silic on diodes, due to a combination of lower forward voltage and reduced recovery time. it is important to select parts with a p eak current rating above the peak coil current and a conti nuous current rating higher than the maximum output load current. it is very important to consider the reverse leakage of the diode when operating above 85c. excess leakage will increase the power dissi pation in the device and if close to the load may create a thermal runaway condition. the higher forward voltage and ove rshoot due to reverse r ecovery time in silicon diodes will increase the peak voltage on the sw output . if a silicon diode is us ed, care should be taken to ensure that the total voltage appearing on th e sw pin including supply ri pple, does not exceed the specified maximum value.
preliminary TTP933 2013/08/23 page j 22?25 ver. j 1.2 . package information sot23-6 ( TTP933-fa6 ) to252-5 ( TTP933-he5 )
preliminary TTP933 2013/08/23 page j 23?25 ver. j 1.2 msop8 ( TTP933-bm8 ) sop8 (TTP933-co8, TTP933-do8, TTP933-jo8)
preliminary TTP933 2013/08/23 page j 24?25 ver. j 1.2 sot89-5 ( TTP933-gg5 ) sot23-5 ( TTP933-ea5 )
preliminary TTP933 2013/08/23 page j 25?25 ver. j 1.2 .order information 1. package form: TTP933-bm8, TTP933-co 8, TTP933-do8, ttp1933-ea5, TTP933-fa6, TTP933-gg5, TTP933-he5, TTP933-jo8 2. chip form: tcp933 . revise history 2013/03/05: original version v1.0. 2013/05/02: modify package information v1.1. 2013/08/23: modify package information v1.2.

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