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BQ76922: Blocking leakage currents in parallel paths BQ76922

Dominik Nogalski
Prodigy 30 points

Part Number: BQ76922
Other Parts Discussed in Thread: BQ76952,

Hi, I would like to implement blocking leakeage current circuit in a BMS based on BQ76922 with parallel paths for charging and discharging. I intend to use charge Path Blocking FET on the basis of your document "Parallel Paths with the BQ76952 Battery Monitor Family". 

I'm wondering if RCHG1 should be placed above Q3 and then I should use same resistance values for RCHG1 and RCHG2 e.g. 5k1? Or leave it as it is in the schematic and then select diffrent resistors RCHG1 and RCHG2?

How select appropriate values for resistor RCHG1, RCHG2 and RG1?

image.png

 

  • 0
    TI__Expert 4490 points

    Hi Dominika,

    Thanks for reaching out.

    This concept was made several years ago and the author is no longer in TI. 

    From my perspective, the current placement of RCHG1 will affect the switching speed of both Q1 and Q3. Due to the additional RG1, the Q3 switches slower than Q1. When CHG is on Q1 is on, Q3 is then on, so Q2 is on. The turn-on delay between these FETs should only be tens of micro-seconds. I would recommend the resistor pinout above Q3 for debug purpose. You need select the resistance based on the FET you choose.

    BRs

    Kian