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BQ76920: Output Amp capacity for Charge/Discharge FET driver

FJ
Intellectual 310 points
Part Number: BQ76920
Other Parts Discussed in Thread: BQ76940, BQ76930, BQ76200

What is the Charge/Discharge FET driver amperage of Bq76920?

I am interested in using this device to replace a current design that utilizes an IXYS 9 amp mosfet driver to provide gate switching to 10 IRLB3813PBF N channel mosfets.

Would I need to use a driver or should the Bq76920 be able to control Mosfets alone? 

  • 0
    TI__Guru 73723 points

    Hi FJ,

    The BQ76920 is a battery monitor IC that monitors 3-5 cell voltages and will disable charge and discharge FETs in the event of any protection being triggered (cell over-voltage, under-voltage, over-current, short-circuit, for example). It is probably not suitable as a FET Driver since it will automatically disable the FETs if a protection trigger is detected and it needs many pins connected to proper voltages to satisfy the protection conditions. 

    Did you mean the BQ76200? The BQ76200 was created for the BQ769x0 family of battery monitors to enable driving high-side FETs  (BQ76920, BQ76930, BQ76940). Some users do use it stand-alone in non-battery applications. This document shows many example configurations driving multiple FETs in parallel: https://www.ti.com/lit/an/slva729a/slva729a.pdf 

    TI has a full line of FET driver ICs that can be seen at the link below. There is a different group of experts that supports these products (I am in the battery team). If you have questions about any of these other FET driver devices, I suggest starting a new thread so that your question gets to the correct experts. 

    https://www.ti.com/power-management/gate-drivers/overview.html 

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Intellectual 310 points

    Matt,

    I will be using the  BQ76920 in a BMS to monitor 5 cell voltages.  My question is what amperage does the CHR/DIS drive outputs have?

    FJ

  • 0 in reply to FJ
    TI__Guru 73723 points

    Hi FJ,

    Thanks for clarifying, I understand now. The BQ76920 FET drive outputs have a 5k nominal ON resistance. From the switching speed spec, the output resistance when the FET is on is ~5k which will limit the output current to approximately 12V/5k = 2.4 mA. This means this device can drive one or two FETs with moderate current. For higher current FETs for for larger FET arrays, an external driver IC or circuit may be needed to adequately switch the FETs. The BQ76200 in combination with the BQ76920 may be helpful for this.

    Best regards,

    Matt