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BQ76952: About reducing bq76952 power consumption from hardware

JH Zhang
Prodigy 210 points
Part Number: BQ76952

Hi TI experts,
When I was designing the schematic diagram of the bq76952 solution, I planned to reduce the power consumption of the bq76952 through hardware design. As shown in the figure, I added a PMOS control switch to the BAT power supply input and the LDO input of REGIN. That is, when my battery is not in use, the BAT power supply input There is no power input for the BAT pin and REGIN input pin. Only when a battery is needed, the BAT pin and REGIN are powered. Other wiring such as sampling lines are the same as the typical circuit diagram to reduce the power consumption of the bq76952.
What I want to know is that when the battery is not used, the BAT pin and REGIN pin have no power input, but the sampling pin has input. Can it be designed like this? Will this cause damage to bq76952? Or what impact will it have?

  • 0
    TI__Mastermind 25605 points

    Hi JH,

    Is there a reason that SHUTDOWN mode is not an option? The typical supply current in SHUTDOWN mode is only 1uA.

    Regards,

    Max Verboncoeur

  • 0 in reply to Max Verboncoeur
    Prodigy 210 points

    Hi Max,
    Because the situation when the system is powered off is random, the battery can be directly hot-swapped and uninstalled. There is no guarantee that the MCU will send a SHUTDOWN command to the AFE before removing the battery, so the battery is working at normal power consumption at this time.


    As I asked before, when I randomly unloaded the battery, I switched the power supply of the BAT pin and REGIN pin through hardware design and disconnected the AFE power supply to achieve the purpose of reducing power consumption. But now I am not sure whether this design will cause damage to the AFE or have other adverse effects. I hope you can give some suggestions on the feasibility of such a design.

  • 0 in reply to JH Zhang
    TI__Mastermind 25605 points

    Hi JH,

    It should be fine; however, you may also consider using the RST_SHUT pin to send the device into SHUTDOWN mode as an alternative. Asserting RST_SHUT high for >1s will trigger the device to enter SHUTDOWN mode and may be a simpler solution to implement.

    When the device is disconnected from a load/charger (no current flowing through the sense resistor), the device can also autonomously enter SLEEP mode. SLEEP mode is not as low IQ as SHUTDOWN mode, however it may be another alternative for you to consider.

    Regards,

    Max Verboncoeur

  • 0 in reply to Max Verboncoeur
    Prodigy 210 points

    Hi Max，

    As you said "Asserting RST_SHUT high for >1s will trigger the device to enter SHUTDOWN mode", I thought of another solution. Through hardware circuit design, I ensure that the RST_SHUT pin of the AFE is pulled low when using the battery, and when I unload After the battery is removed, the AFE RST_SHUT pin in the battery will be pulled high to 3.3V and remain high, so that the AFE can enter SHUTDOWN mode. Can this design also achieve low power consumption when not in use?

  • +1 in reply to JH Zhang
    TI__Mastermind 25605 points

    Hi JH,

    That's a good idea. One consideration to make is that when the battery is plugged back in, the RST_SHUT will have to go low, then the TS2 pin will have to be pulsed low and then released again to fully wake the device.

    Regards,

    Max Verboncoeur