BW7385 non-isolation buck current control ic with high pfc for led lighting ver 1.01 mar. 2014 1 features thd and efficiency adjustable by rt pin low thd <15% (adj) accuracy constant current (2.5%) high power factor (>0.9) low bom cost boundary current mode control gate output voltage clamp led open protection(ovp) led short protection(scp) over current protection (ocp) over thermal protection(otp) sot26 package available applications led lighting down light tube lamp par lamp bulb order information description the bw 7385 is a thd and efficiency adjustable, high accuracy and high power factor constant current pwm controller. this is capable of controlling thd and efficiency optimization by an external resistor. these functions enable the led driver to easily meet rule of led current requirements the ic achieves high power factor and high efficiency by bcm mode. the line and load regulation of led current is about 2.5% because of particular control method. bw 7385 also provides gate driving voltage clamping, vcc over voltage protection and system output open/short circuit protection to increase ic performance. pin configurations (top view) sot-26 shipping: r: tape & reel kf: sot-26 circuit type vcc gnd ou t c s rt com 1 2 3 4 6 5 bw 7 3 8 5 - k f r bw
bw 7385 non-isolation buck current control ic with high pfc for led lighting ver 1.01 mar. 2014 2 pin descriptions pin name pi n description com output pin of error amplifier. gnd ground return for all internal circuit. cs input current sense pin. out gate driver output. vcc power supply pin for all internal circuit. rt efficiency / thd option pin. typ ical application circuits figure 1
bw 7385 non-isolation buck current control ic with high pfc for led lighting ver 1.01 mar. 2014 3 absolute maximum ratings (note 1) parameter symbol range unit power supply pin v cc 40 v rt voltage to gnd v rt -0.3 t o 5.5 v out voltage to gnd v out -0.3 t o 40 v cs voltage to gnd v cs -0.3 t o 5.5 v com voltage to gnd v com -0.3 to 5.5 v junction temperature range t j -40 to +150 c storage temperature range t stg -65 to +150 c lead temperature (soldering 10 sec) t lead 260 c power dissipation @t a =25 c p d 0.3 w thermal resistance junction to ambient (note 2) ja 220 c/w thermal resistance junction to case jc 106.6 c/w esd rating (human body mode) (note 3) v esd 2 kv esd rating (machine mode) (note 3) v esd 200 v recomme nded operating conditions (note4) parameter symbo l operation conditions unit power supply pin v cc 33 v rt voltage to gnd v rt -0.3 t o 5 v out voltage to gnd v out -0.3 t o 19 v cs voltage to gnd v cs -0.3 t o 5 v com voltage to gnd v com -0.3 t o 5 v operating junction temperature range t j -40 to +125 c operating ambient temperature range t opa -40 to +85 c note 1: stresses listed as the above absolute maximum ratings may 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 maximum 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 function outside its ope r ating conditions.
bw 7385 non-isolation buck current control ic with high pfc for led lighting ver 1.01 mar. 2014 4 block diagram figure 2
BW7385 non-isolation buck current control ic with high pfc for led lighting ver 1.01 mar. 2014 5 electrical characteristics v cc =18v, t a =25c, unless otherwise specified. parameter sym bol condition min typ max unit supply voltage start-up current v cc(st) v cc = v uvlo(on) -1v 45 u a operating current i opa with 1nf load on out pin 2.1 2.6 ma uvlo(off) v uvlo(off) 7 8 9 v uvlo(on) v uvlo(on) 16 17.5 19 v ovp level on vcc pin v ovp 29 31 33 v voltage feedback feedback reference voltage v fb 0.1 96 0.2 0.204 v trans conductance g m 58 u s output sink current i o-sink 5.8 ua output source current i o-source 5.8 ua current sensing cs limit voltage v ocp 1.4 v open loop voltage, cs pin open v olp 5 v leading-edge blanking time leb 400 ns delay to output 100 ns switching frequency start frequency t str 3 4 .5 6 khz gate driver output rising time t rise load capacitance =1nf 90 n s falling time t fail load capacitance =1nf 40 n s vgate-clamp v gate 12. 5 15 v thermal section thermal shutdown 150 thermal shutdown release 120 note 5: guaranteed by design. note 6: auto recovery type.
bw 7385 non-isolation buck current control ic with high pfc for led lighting ver 1.01 mar. 2014 6 application information start-up current the typical start-up current is around 45ua. 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 bw 7385 the turn-on and turn-off thresholds level are fixed at 17.5v and 8v respectively. this hysteresis shown in fig.3 ensures that the start-up capacitor will be adequate to supply the chip during start-up. for quickly star-tup the led driver, the start-up resistor should be matched with the start-up capacitor. due to the low uvlo on level, so the turn-on delay time will also never greater than the general pwm ic. 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 400ns 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 cannot switch off the gate driver. ocp(over current protection) the bw 7385 is built cycle by cycle over current protection function on cs pin. as the cs pin voltage is larger than v ocp (1.4v), the gate output will be turned off immediately to avoid the driver board be burned out. ovp (over voltage protection) on vcc to prevent the led driver from being damaged, the bw 7385 is implemented an ovp function on vcc. when the vcc voltage is higher than the v ovp (31v), 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 until the vcc pin voltage is down to the uvlo off level. the bw 7385 is working in an auto-recovery mode as shown in fig. 4. gate cl amp driver is clamped to 12.5v by an internal clamping circui t to avoid the gate of mosfet be damage. fig. 3 fig. 4
bw 7385 non-isolation buck current control ic with high pfc for led lighting ver 1.01 mar. 2014 7 package outline dimensions note: information provided by bruckewell is believed to be accurate and reliable. however, we cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an bruckewell product; nor for any infringement of patents or other rights of third parties that may result from its use. we reserve the right to change the circuitry and specifications without notice. life support policy: bruckewell does not authorize any bruckewell product for use in life support devices and/or systems. life support devices or systems are devices or systems which, (i) are intended for surgical implant into the body or (ii) support or sustain life, and whose failure to perform, when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. typical numbers are at 25 c and represent the most likely norm.
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