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I am using a TI BQ76940 battery management IC for a project. I want to implement fast charging in this system. How can I go about achieving it? Can I connect multiple high-side bidirectional MOSFETs in parallel along the CHG and DSG pins?

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  • \$\begingroup\$ I have a follow up question. While charging, the CHG pin should go high and DSG pin low. How will the current flow when the DSG mosfet is OFF and its body diode is reverse biased? \$\endgroup\$
    – BlackHawk
    Jan 3, 2022 at 7:14

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I want to implement fast charging in this system. How can I go about achieving it?

This requires an external circuit to be designed that sets the charging current.

The BQ76940 is not a charger circuit; it is a cell-balancer circuit. The charging circuit is external to this device and, when designing a charger circuit, you must consider that the BQ76940 can only deal with balancing currents of up to around 5 mA per cell. So, if you are using a fairly small charger current, the internal balancing current capabilities of the BQ76940 can handle a fairly wide range of cell discrepancies and, as a result, it will adequately keep all series cells at about the same state of charge.

However, if you go to a higher charge demand (set by your external circuit, you may start to have problems. I suggest you read the data sheet thoroughly to understand the implication of how far you can push this device before hitting limits.

Can I connect multiple highside bidirectional MOSFETs in parallel along CHG and DSG pins?

The charging current is set by an external charge circuit.

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  • \$\begingroup\$ I have a follow up question. While charging, the CHG pin should go high and DSG pin low. How will the current flow when the DSG mosfet is OFF and its body diode is reverse biased? \$\endgroup\$
    – BlackHawk
    Jan 3, 2022 at 6:28
  • \$\begingroup\$ It's body diode won't be reverse biased during charging; charge current can flow from the bottom of the battery pack through the body diode and return to PACK-. \$\endgroup\$
    – Andy aka
    Jan 3, 2022 at 8:47
  • \$\begingroup\$ So. during charging the current flows from PACK+ to PACK - and during discharge current flows from PACK - to PACK + ? \$\endgroup\$
    – BlackHawk
    Jan 3, 2022 at 9:34
  • \$\begingroup\$ @BlackHawk that's how I read it to be. \$\endgroup\$
    – Andy aka
    Jan 3, 2022 at 9:38

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