LTC7004 Failure

I was using a LTC7004 to control the ON/OFF of a 8series LiIon battery. The nominal input voltage is 29.6V, the load is a constant power 160W camera. Use an electric load to do 160W constant power discharging test, sometime the LTC7004 is found broken

When the discharging for the input battery is done, the undervoltage protection is on and there is no output (at this moment INP of the LTC7004 is 3.3V and load is 160W), the LTC7004 is more likely to be broken.

Failure description: connect INP pin with either 3.3V or 0V, the TG and TS voltages of LTC7004 are the same, which leads to the disconnection of NMOS. When electrified, the impedance between TG and TS of LTC7004 is 1.6Ω (using a multimeter to check). When not electrified, the impedance is infinitely great.

More tests: I tested the earth impedance of each pin with a multimeter, and compared the impedance with that of a normally functional LTC7004 and found no problem.

Could anybody help me with the reason why the LTC7004 is broken and how can I do to with it?

  • Hi

    Is D30 placed close to TS pin and GND pad on the PCB board?  Since the load is constant power load, load current could be high when the under voltage protection is ON.  This load current with cable/trace to the load inductance can pull TS pin below GND.  D30 diode should be placed as close as possible to TS pin.

    I also noticed that turn ON slew rate has been slow down by R27 and C53.  Check the power MOSFET SOA curve rating and make sure voltage and current across the power MOSFET during turn ON doesn't exceed the rating.

    I would recommend using the ultra low leakage diode such as BAS116,BAS416, and BAQ34 diode instead of 1N4148 diode.  I would also recommend using 4.7uF cap value for C52 instead of 0.1uF.

  • I have several questions to your last reply 

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