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BQ40Z50-R1: BQ40Z50-R1 ASCD issue in sleep mode

Dean Cheung
Prodigy 40 points
Part Number: BQ40Z50-R1

Hello,

The issue, DSG FET always be damaged with short ciucuit test, ocurred when bq40z50-R1 sleep wihout communication. We faund from attched file the short circuit current (>175A)  rebounded and appeared again after ASCD  had been triggered for 150ms. The first ASCD protection cannot  be latched. Test the battery without communication about bq40z50-R1.xlsx

To avoid damaging FET too easily, We also tested AOLD and got the same resault with the same sleep condition. Unless disable sleep, it's OK.

So how to ensure it can be protected normally in sleep mode when short circuit ？

please do me a favor about it.

Thank you very much.

  • 0
    TI__Guru** 105770 points

    Hello Dean,

    We'll look into this problem and get back to you soon.

    Sincerely,

    Wyatt Keller

  • 0
    TI__Mastermind 34775 points

    Hello Dean,

    The difference you are seeing between NORMAL mode and SLEEP is the FW protection is triggering faster in NORMAL mode protecting the DSG FET. The current in NORMAL mode is sampled more frequently in NORMAL mode that SLEEP (power savings). The ASCD is an analog protection feature and is independent of FW mode NORMAL or SLEEP. It's also non-latching, so every time DSG turns off it will recover and trigger again. This will repeat until short condition is removed or some other fault stops it or in your case the DSG FET gets damage.

    What you can do for non-latching current protection is to set the recovery threshold to the opposite state. If it's a discharge current protection set recovery current to charge state, so it would require a charger to recovery hence latching it.

    AOLD is kind of tricky to use since it has a latch counter and a recovery and decrement time counter, so if not configure correctly it may not latch in the time that you want it to and your DSG FET will be damaged as you observed.