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Problem with LTC4015

Question asked by AndreyKasper on Aug 10, 2018
Latest reply on Aug 15, 2018 by Zack

Hello. 

I have a problem with trying to reach 16A charging current with Vin = 28 V, while charging Li-Ion 6S Battery. The way I increasing current is adding resistors to input and output shunts. Maximum current I get is 8A. After adding the next fourth resistors to get near 12 A current, when the battery is pluged, there was a spark with a fire and fume from the chip. Low side MOSFET was damaged and connection to pin CSP was burnt.  I removed the chip and see the voltage on SYS and SW pins when battery is plugged (FETs gates are connected with the sourses). Vsys and Vws do not exceed Vbat+2V. Any way after repairing my PCB I can't get any charging current. When I turn on the power without battery I can see the process of battery testing. After that I can read bat_short_fault bit is set high (the LED is conncted on Vbat). Then I turn off the power, plug the battery, turn on the power again and read cc_cv_charging bit is set high, but no current is. The reason I've found is low MOSFET driver is damaged (about 30 Ohms resistanse from GND to BG , but low FET is OK). Next trying with a new chip ended with the same result (about 80 Ohms in both directions between GND and BG and MOSFET is OK). I think low drain to sourse voltage of lower MOSFET could be the reason, but I'm not sure. 

It will be great if you recomend me some values of parts and FETs to get charging current 16A.

P/S: High FET BSC093N04LS, Low FET BSC093N04LS, Inductor 3.3 uH, Frequency 500 kHz, 40 mkf ceramic on Vbat, 100 mkf ceramic and 100 mkf electrolitic on Vsys, 40 mkf ceramic on Vin.      

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