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TIDA-00792: BQ76200

Cheng Arvin
Prodigy 100 points
Part Number: TIDA-00792
Other Parts Discussed in Thread: BQ76200, , BQ76940

Hi TI,

Based on BQ76200 datasheet, AFE's BAT pin has Rf to connect to BQ76200's Rfilter,

I just confuse why TIDA-00792 without show this part and I think Rf connect function can avoid BQ76200's BAT pin pull low when short circuit happen.

Could you please give me some suggestion about BQ76200's BAT pin design. Thanks.

BR

Arvin

  • 0
    Prodigy 100 points

    as below is BQ76200 reference diagram

  • 0 in reply to Cheng Arvin
    TI__Guru 54715 points
    Hi Arvin,
    The schematic of TIDA-00792 is drawn slightly differently from the block diagram in the bq76200 data sheet, but the basic power connection is the same: The bq76940 BAT pin Rf (R34) comes from the BATT+. The bq76200 BAT pin filter resistor (R3) also comes from BATT+. The block diagram routes a BATT+ line across the page before splitting to the different resistors.

    It is important for the bq76200 BAT to reference the FET source voltage so that the gate level is driven to the proper voltage.
    During short circuit the bq76940 BAT pin will be held up by the large filter components while the bq76200 small filter will let its BAT pin voltage fall quickly to the FET level. This is good since the operating voltage for the FET driver comes from VDDCP which is referenced to the BAT pin. See figure 5 or 25 of the FET configuration apnote www.ti.com/.../slva729. Notice that the DSG voltage follows the BATT+ voltage during the application of the current.
  • 0 in reply to WM5295
    Prodigy 100 points

    Hi WM5295,

    Thanks for your answer.

    If worry BQ76200 BAT pin voltage when short circuit, maybe add diode to BQ76200 BAT pin.

    Whether BQ76200 will impact to BQ769X0, add Diode for BQ76200. How about this idea. ha ha.

    Best Regards

    Arvin 

  • 0 in reply to Cheng Arvin
    TI__Guru 54715 points
    Hi Arvin,
    The bq76200 does not need the diode. During short circuit it will operated from the VDDCP, it just may not have enough BAT voltage to run the charge pump during that time so the CVDDCP must maintain the voltage.
    Some designers want a diode to block possible charge in case they short multiple bq76200 pins together. If you use a diode take precautions to avoid damage the the FET gate.