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CSD23382F4: P-channel FET as reverse battery protection

Shlomi Yehezkia
Mastermind 6150 points
Part Number: CSD23382F4
Other Parts Discussed in Thread: BQ25120A, , CSD25484F4

Hi Team,

Can you please check battery reverse protection FET configuration.

I want to use p-channel FET as reverse battery protection.

I payed attention in the previous design that BQ25120A doesn't support this option.

Thanks,

Shlomi

CSD23382F4.pdf

  • 0
    TI__Mastermind 31845 points

    Hi Shlomi,

    Thanks for your interest in TI FETs. The circuit implementation looks OK to me. However, the symbol for Q4 shows a NFET when in fact, the CSD23382F4 is a P-channel FET. When the battery is connected with the correct polarity, the body diode of the FET will conduct first until the source voltage is high enough to enhance and turn on the FET. If the battery is connected with the incorrect polarity, the body diode will block any current flow. Please be aware that the CSD23382F4 uses back-to-back ESD gate protection diodes and will have much higher leakage, IGSS, than a FET without the ESD protection. I am going to send this to the apps team for the BQ part to have them review as well.

  • 0 in reply to John Wallace1
    Mastermind 6150 points

    Hi John,

    Can you suggest other CSD23382F4 without ESD protection?

    Thanks,

    Shlomi

     

  • 0 in reply to Shlomi Yehezkia
    TI__Mastermind 31845 points

    Hi Shlomi,

    All of our P-channel FemtoFETs have ESD protection. The CSD23382F4 uses back-to-back diodes and all of the others have a single diode from gate-to-source. A comparable device with single diode is the CSD25484F4. The leakage, IGSS, is much lower. However, for the single diode, if the source is pulled below the gate, then the diode will be forward biased and conduct current. In your application, if the battery is connected in reverse polarity then the diode will conduct. This will not occur with the CSD23382F4 because of the b2b diodes. If you choose to use a FET with a single diode, then you may want to add a gate resistor to limit the current. The CSD25484F4 has a 20 ohm (nominal) series gate resistance integrated.