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BQ25720: Can CELL_BATPRESZ be used to control BATDRV?

David Bleakley
Prodigy 211 points
Part Number: BQ25720

Tool/software:

Hi,

I understand that pulling CELL_BATPREZ low will stop the battery from being charged.

If a battery powers the unit, will pulling CELL_BATPREZ low also pull BATDRVN low and disconnect VBAT from VSYS?

If this is possible then I can power down VSYS.

VSYS powers some regulators with a high shutdown leakage.

  • 0
    TI__Mastermind 33205 points

    Hi, David,

    When the AC adapter is available, pull down CELL_BATPRESZ pin => turn-off BATFET and disable charging. =>The system is powered by the AC adapter in this case. Vsys is slightly higher than the VBAT. 

    When the AC adapter is unavailable, CELL_BATPRESZ pin has no impact on the BATDRV. The BATFET is always ON, thus allowing VBAT to supplement the VSYS regardless of the CELL_BATPRESZ pin. 

    I hope this helps. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 211 points

    Thanks, , This is helpful.

    Is there a pin that can power down the BQ25720, its VSYS or the BATDRV?

    I am trying to save power when the system is on standby.

    Is the only way to disable BATDRV when in battery mode using i2c: BATFET_ENZ ?

    Is VBUS power the only way to re-enable this?

  • +1 in reply to David Bleakley
    TI__Mastermind 33205 points

    Hi, David,

    For achieve low quiescent current, TI suggests enabling low power mode. The internal logic is OFF, except the communication and a few critical logic. The IQ is the lowest.

    There is no shutdown pin. When VBUS is re-applied, the low power mode is ignored, the part runs in full performance mode. I don't think BATDRV has any impact on the IQ. BATFET is a PFET with a body diode. VBAT supplements the VSYS regardless of the BATDRV. 

    Regards,

    Tiger