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Original question:

BQ34Z100-R2: BQ34z100-R2 About Design Energy parameter setting

BQ76952: Bq76952 shutdown mode

korcan tuna
Intellectual 290 points
Part Number: BQ76952
Other Parts Discussed in Thread: BQ34Z100-G1, BQSTUDIO

Tool/software:

Dear Team,

I have a question regarding the 76952 registers and would appreciate your support.

Our current design utilizes the BQ76952 and BQ34Z100-G1 for a battery pack consisting of 15 series LiFePO4 cells. The TS2 pin of the BQ76952 is used to wake the IC from shutdown mode via a button. However, when the PCB is initially energized, the IC automatically wakes up, and the button does not function as expected. This means that every time the battery pack is mounted or dismounted, the IC remains in the wake state.

If the shutdown command is sent via BQStudio, the IC enters shutdown mode. In this condition, the IC remains in shutdown mode regardless of whether the battery pack is mounted or dismounted. The button is only functional in this state, allowing the IC to wake from shutdown mode.

I would like to configure the system so that the IC always wakes from shutdown mode using the button, while also ensuring that the IC enters shutdown mode when there is no energy(battery pack). How can this be achieved?

Thank you for your support.

  • 0
    TI__Genius 17795 points

    Hello Korcan,

    The device when initially powered on does not need the TS2 pin to wake up from SHUTDOWN mode. It can also wake up from the LD pin being pulled above ~1.45V.

    To combat inadvertent WAKEUP during SHUTDOWN mode, the BQ769x2 can be configured to automatically re-enter Shutdown mode after a period of time as well.

    More information regarding SHUTDOWN mode and that feature can be found in this SHUTDOWN Mode FAQ.

    Best Regards,
    Alexis

  • 0 in reply to Alexis_H
    Intellectual 290 points

    Dear Alexis,

    Thank you for your detailed response. I appreciate your support. However, I would like to clarify an issue.

    I have measured TS2 using an oscilloscope, and all registers are set to their default values for the BQ76952. Regarding the TS2 protection state:

    • TS2 remains high until a shutdown command is sent to the IC, even when the power is disconnected (battery pack mounting or dismounting).
    • TS2 remains low until a wake-up command is sent (TS2 is pulled down).

    This behavior presents a challenge in mass production. When the PCB is mounted to the battery pack, the BQ76952 automatically wakes up from shutdown mode.

    Could you advise on how to ensure that the IC remains powered off initially until it is manually woken up via a switch (by pulling TS2 down)?

    Note: In all tests, the LD pin has consistently remained low.

    Best regards,

  • +1 in reply to korcan tuna
    TI__Genius 17795 points

    Hello Korcan,

    Thank you for clarifying. While TS2 and LD are the most common ways the device wakes up, there is an exception to the typical WAKE procedure which is SHUTDOWN caused by low Vbat voltage. If voltage is brought up from below VPORA-VPORA_HYS, then the device will also wake up. I believe this can be avoided by changing the Power:Shutdown:Shutdown Stack Voltage. This is mentioned in ‘Exiting SHUTDOWN MODE’ of the FAQ.

    Best Regards,
    Alexis