bw 7386 accuracy constant current led driver rev 2.0 aug. 2013 ! 1 features z accuracy constant current z low bom cost z current mode/fixed frequency control z gate output voltage clamp z led open protection(ovp) z over current protection (ocp) z 300ma driving capability for out pin applications z e26/27, t5/t8 led lamp z others led lighti ng applications description the bw 7386 is a highly-integrated, low startup current, current mode, and fixed switching frequency pwm controller. these functions enable the led driver to easily meet the accuracy average led current requirements. the integrated functions also include the led open protection, and internal over temperature protection. the comp pin controls the duty by connected an rc compensation network to ground and forming the closed loop feedback control. to protect the external power mosfet from being damaged by supply over voltage, the bw 7386 ou t pin voltage is clamped to about 17v. the bw 7386 improves the performance and reduces the cost of the led driver. it is a 6-pin sot-26 package. order information pin configurations (top view) bw 7386 - k f r circuit type kf:sot-26 shipping r : r e e l t : tube bruckewell
bw 7386 accuracy constant current led driver rev 2.0 aug. 2013 ! 2 pin descriptions pin name pin description vcc power supply pin gnd ground pin out the output driver for driving the external mosfet dim dimming control pin by input a dc voltage comp feedback compensation network cs current sense pin, connect to sense the mosfet current typical application circuits led+ led- vac (90v~264v) gnd 2 out 3 dim 4 comp 5 cs 6 vcc 1 bw 7386
bw 7386 accuracy constant current led driver rev 2.0 aug. 2013 ! 3 absolute maximum ratings (note 1) parameter symbol range unit power supply pin v dd 3 0 v dim voltage to gnd v dim - 0 . 3 t o 7 v cs voltage to gnd v cs - 0 . 3 t o 7 v out voltage to gnd v out 1 5 v maximum junction temperature tj 150 c storage temperature rang t stg - 6 5 t o + 1 5 0 c lead temperature (soldering 5 sec) t lead 260 c power dissipation @t a =25 c p d 3 0 0 m w thermal resistance junction to ambient (note 2) , ja 333 c/w thermal resistance , jc 1 0 6 . 6 c / w esd rating, human body mode (note 3) v esd 2 k v esd rating, machine mode (note 3) v esd 2 0 0 v recommended operating conditions (note 4) parameter symbol operation conditions unit supply voltage v dd 2 6 v operating junction temperature range t j 150 c operating ambient temperature range t opa -20 to +85 c note 1: stresses listed as the above absolute maximum ratings ma y cause permanent damage to the device. these are for stress ratings. functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute ma ximum rating conditions for extended periods may remain possibility to affect device reliability. note 2: thermal resistance is specified with the component mounted on a low effective thermal conductivity test board in free air at t a =25 c. note 3: devices are esd sensitive. handing precaution recommended. note 4: the device is not guaranteed to func tion outside its operating conditions.
bw 7386 accuracy constant current led driver rev 2.0 aug. 2013 ! 4 block diagram cmpdl!ejbhsbn com ptd pof! tipu esjwfs pro (vcc_ovp, otp) out cs vref rst set clk vwmp0ch vcc gnd ts mbudi s r q vref ovp_vcc g m dim pdq ejnnjoh current to voltage
bw 7386 accuracy constant current led driver rev 2.0 aug. 2013 ! 5 electrical characteristics v cc =15v, t a = 25c, unless otherwise specified. parameter symbol condition min typ max unit supply voltage startup current v dd(st) v cc =uvlo on -1v 8 ua operating current v comp with 1nf load on out pin 1.5 2.5 ma operating current i opa with 1nf load on out pin protection tripped (ocp, ovp, scp,otp) 1.2 1.8 ma uvlo(off) 7 8 8 v uvlo(on) 17 18 19 v ovp level on vcc pin ovp 26 28 30 v voltage feedback feedback reference voltage v fb 0.194 0.2 0.206v tran-conductance 120 us output sink current i o-sink 1 2 u a output source current i o-source 1 2 u a current sensing input over voltage protection f osc 0.8 v open loop voltage, cs pin open 5 v leading-edge blanking time 410 ns delay to output 100 ns switching frequency switching frequency 42 45 48 khz maximum duty 90 % frequency jitter range +/-6 % te m p . sta b i l i ty -40w! ~125 w 6 % voltage stability v cc =11v~25v 1 % gate driver output rising time load capacitance = 1000pf 160 ns falling time load capacitance = 1000pf 80 ns vgate-clamp v cc =25v 17 19 v
bw 7386 accuracy constant current led driver rev 2.0 aug. 2013 ! 6 dim input section saturation threshold voltage 3.0 v linear dimming range 0.6 3.0 v current source 270 300 330 ua thermal section thermal shutdown t sd 150 w
bw 7386 accuracy constant current led driver rev 2.0 aug. 2013 ! 7 application information start-up current the typical start-up current is around 8ua. 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 BW7386 the n the turn-on an turn-off thresholds level are fixed at 18v and 8v 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 le d 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. oscillator the maximum duty-cycle of in ternal oscillator is up to 90% for driving high led voltage string. the frequency of the oscillator is fixed to 45khz by internal setting. 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 410ns 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. ocp(over current protection) the BW7386 has an over current protection function on cs pin. an internal circuit detects the current level, when the current is larger than a threshold level, the gate output will keep on low level. then vcc decreases below uvlo off level, the controller resets again. ovp (over voltage protection) on vcc the prevent the led driver from being damaged, the BW7386 is i mplemented an ovp function on vcc. when the vcc voltage is higher than the ovp threshold voltage 28v, 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 (latch off type optional). 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 bw 7386 is working in an auto-recovery mode as shown in fig. 2. fig. 1 uvlo ( on ) 18v uvlo(off) 8v
bw 7386 accuracy constant current led driver rev 2.0 aug. 2013 ! 8 gate clamp/soft driving driver is clamped to 17v by an internal clamping circuit. those damages usually come from undesired over-voltage gate signals. under the conditions listed below, th e gate output will turn off immediately to protect the power circuit. the bw 7386 also has soft driving function to minimize emi. fig. 2
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