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CSD19536KTT: CSD19536KTT burnt down after 200A discharging current test

Morris Chen82
Prodigy 50 points
Part Number: CSD19536KTT

Hi:

I use 5pcs CSD19536KTT MOSFET in parallel on the PCB in my BMS.

I did the battery pack discharging test for the discharging cuurent 50A(32 sec) ---> 80A(15 sec) ----> 100A(5 sec) ---> 200A(5 sec) ----> idle(10 sec) --->50A(32 sec) ---> 80A(15 sec) ----> 100A(5 sec) ---> 200A(5 sec)....

This cycle is always repeat until the battery capacity is exhausted.

Each MOSFET shares the maximum current 40A when the  discharging cuurent is up to 200A.

The temeprature of MOSFET is up to 90℃ after the test is done.

After testing several times, I found the 5 MOSFETs of the middle two are occured short and their temperature is over 100℃.

I have no idea of why the reliability of CSD19536KTT is so poor.

Could you have any idea for solving this issue?

Thanks

Morris

  • 0
    TI__Expert 7905 points
    Morris,

    Thank you for coming to us and using our MOSFETs.

    A lot of care needs to be taken when paralleling 5 MOSFETs to handle high current due to static and dynamic current sharing among those FETs. Unfortunately, assuming a perfect current sharing (40A/FET) is not realistic in your application. It is possible you are actually putting all the current through much less than 5 MOSFETs.

    Here are a few tips on how to improve current sharing between power MOSFETs:
    1. PCB layout needs to be symmetrical for all FETs, including the gate-source and drain source loop.
    2. Switching speed needs to be tuned to allow all FETs to turn-on and off with about the same delay. A few ns of delay mismatch will overstress the FET and cause possible FET damage.
    3. Each FET needs to be have its own external Rg to prevent oscillation during switching.

    We do not have a specific application note on this but if you do a google search on paralleling power MOSFETs you can find a lot of literature about how to parallel MOSFETs.

    If you are still having issues or already have done the tips above I would suggest you contact your local TI support team and they can bring in the right technical resources to help you out.