1 p r e li m i n ary bw7385 a features tm (transition mode) fixed on -time pfc control accuracy constant current low bom cost inductor size reduction ct pin adjust frequency range for optimization over voltage protection (ovp)-auto recovery led short protection (scp) -auto recovery over load protection (olp) -auto recovery sot-26 package compatible inductance ballast incompatible electronic ballast application gu10 /e14 led bulb others led lighting applications description the bw7385 a is a highly-integrated, low startup current, tm (transition mode), fixed on- time pfc control and pwm controller. these functions enable the led driver to easily meet the accuracy average led current and high power factor requirements. the integrated functions also include the led short protection, over voltage protection, over load protection. the comp pin controls the duty by connected an rc compensation network to ground and forming the closed loop feedback control. the bw7385 a improves the performance and reduces the cost of the led driver. it is a 6-pin sot-26 package. high power factor & accuracy constant current led driver
2 pin configuration pin description pin no. name function 1 vcc power supply pin 2 gnd ground pin 3 drv the drv pin is connected to the totem pole gate driver to drive the external power switch. 4 ct the ct pin is connected to the current source to charge the external capacitor and compare the comp voltage to terminate the power switch. 5 cs current sense pin 6 comp feedback compensation network absolut e maximum ratings supply voltage vcc --------------------------------------------------------------------------------------------------------- 30v ct, comp, cs ---------------------------------------------------------------------------------------------------- -0.3v ~ 7v drv ------------------------------------------------------------------------------------------------------- 15v junction temperature ------------------------------------------------------------------------------------------------------- 150 operating ambient temperature ------------------------------------------------------------------------------ -20 ~ 85 stor age temperature range ---------------------------------------------------------------------------------- -65 ~ 150 sot- 26 package thermal resistance (junction to ambient) ----------------------------------------------- 250 /w power dissipation (sot-26, at ambient temperature = 85 ) ------------------------------------------------ 250mw lead temperature (all pb free packages, soldering, 10 sec) -------------------------------------------------- 260 esd voltage protection, human body model -------------------------------------------------------------------------- 2kv esd voltage protection, machine model ----------------------------------------------------------------------------- 200v p r e li m i n ary BW7385A
3 function block internal bias & vref vcc ok a ll blocks vcc uvlo vc c ovp 31.5 v + - protection en debounce gnd cs + - current l im it ocp comp vref ok driver s t age out qr s + - r vref gm ct starter on time c o ntroller sawtooth g e nerator current detector p r e li m i n ary BW7385A
4 application circuit p r e li m i n ary BW7385A
5 electrical characteristics (vcc = 15.0v & t a = +25 , unless otherwise specified.) parameter pin min. typ. max. unit supply voltage startup current (vcc=uvlo on - 1v) 1 10 50 ua operating current (with 1nf load on out pin), vcomp = 2.5v 1 2.5 3.2 ma operating current (with 1nf load on out pin), protection tripped (ovp, scp,) 1 1.6 2.5 ma uvlo(off) 1 5.5 6.5 7.5 v uvlo(on) 1 14 15 16 v ovp level on vcc pin 1 29.5 31.5 33.5 v ovp de-bounce time 1 40 us voltage feedback feedback reference voltage 6 0.195 0.200 0.205 v tran-conductance 6 300 us output sink current 6 300 ua output source current 6 60 ua current sensing input over voltage protection 5 1.8 2.0 2.2 v open loop voltage, cs pin open 5 5 v leading-edge blanking time 5 450 ns delay to output 5 130 220 ns gate driver output rising time, load capacitance = 1000pf 3 280 500 ns falling time, load capacitance = 1000pf 3 80 150 ns vgate-clamp (vcc = 25v ) 3 12.5 15 v ct output section ct pin current 4 160 180 200 ua p r e li m i n ary BW7385A
6 application information the typical start-up current is around 10ua. very low start-up current allows the pwm controller to increase the value of start-up resistor and then reduce the power dissipation on it. uvlo (under voltage lockout) a hysteresis uvlo comparator is implemented in bw7385 a, then the turn-on and turn-off thresholds level are fixed at 15v and 6.5v respectively. this hysteresis shown in fig.1 ensures that the start-up capacitor will be adequate to supply the chip during start-up. for quickly startup the led driver, the start-up resistor should be matched with the startup capacitor. due to the low uvlo on level, so the turn-on delay time will also never greater than the general pwm ic. fig.1 leb (leading-edge blanking) each time the power mosfet is switched on, a turn-on spike will inevitably occur at the sense resistor. to avoid fault trigger, a 450ns leading-edge blanking time is built in. conventional rc filtering can therefore be omitted. during this blanking period, the current-limit comparator is disabled and can not switch off the gate driver. ovp (over voltage protection) on vcc to prevent the led driver from being damaged, the bw7385 a is implemented an ovp function on vcc. when the vcc voltage is higher than the ovp threshold voltage 31.5v, the output gate driver circuit will be shut down immediately to stop the switching of power mosfet. the vcc pin ovp function is an auto recovery type protection. if the ovp condition happens, the pulses will be stopped and never recovery unless the vcc pin voltage is down to the uvlo off level. the bw7385 a is working in an auto-recovery mode as shown in fig.2. fig. 2 gate clamp driver is clamped to 15v by an internal clamping circuit. those damages usually come from undesired over-voltage gate signals. under the conditions listed below, the gate output will turn off immediately to protect the power circuit. p r e li m i n ary % : a
7 package information sot-26 sot-26 millimeters inches symbol min. max. min. max. a 1.45 0.057 a1 0.00 0.15 0.000 0.006 a2 0.90 1.30 0.035 0.051 b 0.30 0.50 0.012 0.020 c 0.08 0.22 0.003 0.009 d 2.70 3.10 0.106 0.122 e 2.60 3.00 0.102 0.118 e1 1.40 1.80 0.055 0.071 e 0.95 bsc 0.037 bsc e1 1.90 bsc 0.075 bsc l 0.30 0.60 0.012 0.024 0 o 8 o 0 o 8 o note: 1. followed from jedec to-178 ab. 2. dimension d and e1 do not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 10 mil per side p r e li m i n ary BW7385A
8 carrier tape & reel dimensions sot-26 application a h t1 c d d w e1 f 178.0 2.00 50 min. 8.4+2.00 -0.00 13.0+0.50 -0.20 1.5 min. 20.2 min. 8.0 0.30 1.75 0.10 3.5 0.05 p0 p1 p2 d0 d1 t a0 b0 k0 sot-26 4.0 0.10 4.0 0.10 2.0 0.05 1.5+0.10 -0.00 1.0 min. 0.6+0.00 -0.40 3.20 0.20 3.10 0.20 1.50 0.20 (mm) application carrier width cover tape width devices per reel sot -26 8 5.3 3000 p r e li m i n ary BW7385A
9 tape and specification reel so t 26 direction of feed p r e li m i n ary bw7385 a
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