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BQ76952: BQ76952 – Unable to Control PDSG (Pre-Discharge) FET with Subcommands (0x0097, 0x01, W)

Sourabh Malsekar
Prodigy 20 points
Part Number: BQ76952


Tool/software:

Hello TI Team,

I am working with the BQ76952 and trying to configure the Pre-Discharge (PDSG) function so that it turns on first before the main Discharge (DSG) FET during wake-up.

Currently, only the Discharge FET is turning ON — the PDSG output is not being controlled automatically.

Here are my setup details:

  • Device: BQ76952

  • FETOptions Register: 0x9308

    • Bit-4 (PDSG_EN) is enabled.

  • Subcommand Used: Subcommands(0x0097, 0x01, W) → (FET Control)

  • Observed behavior:

    • The device wakes up and enables only DSG, but not PDSG.

    • When I manually issue CommandSubcommands(FET_ENABLE) and CommandSubcommands(PDSGTEST), both FETs toggle correctly, confirming the hardware path is fine.

  • Sleep mode: The pack is in sleep mode before enabling discharge.

Question:

  1. Does the BQ76952 automatically manage PDSG before DSG when PDSG_EN is set, or do I need to explicitly sequence it using commands?

  2. Is Subcommands(0x0097, 0x01, W) (FET Control) expected to control the PDSG FET, or is there a separate sequence for that?

  3. Are there any conditions (like Vcell, CHG/DSG enable flags, or delay timers) that could block the PDSG pin from activating even though PDSG_EN is set?

Any guidance on how to properly configure or trigger the Pre-Discharge FET before the main discharge would be greatly appreciated.

Thanks and regards,
Sourabh S Malsekar