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BQ76952EVM: PCHG and PDCHG FET removal

biter terbi
Prodigy 160 points
Part Number: BQ76952EVM
Other Parts Discussed in Thread: BQ25750

Hello ti forum!
My name's Pedro and I recently acquired this evm.
After some testing we decided to make our own board using this chip. We'll use this bms and a BQ25750 charger.
Given we're installing the smart charger on the board I don't see the point of using the PCHG fet, so I'm probably removing it.
But I don't really understand the point of the PDCHG fet. Is it needed for the "load detection" or the "short circuit detection"?
I'd like to know if removing these two fets has another negative effect other than not having the "precharge" and "predischarge" functionality.
Thank you very much in advance.
Pedro

  • +1
    TI__Genius 11315 points

    Hey Pedro,

    The FETs are only to allow predischarge and precharge functionality. It is not needed for load detection or short circuit detection.

    The use case is that the system can have a large capacitance at its input and some circuit which may discharge it over time.  When the battery is connected and tries to turn on that capacitance looks like a short circuit and can cause a fault in the battery. The pre-discharge circuit allows the battery to charge the capacitance to prevent short circuit at turn on of the DSG.

    Thanks,
    Caleb