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BQ76952: AFE Power consumption from 1mA to 11mA when setting REG1 output 3.3V to MCU

Chen Yang
Intellectual 2770 points
Part Number: BQ76952

Hi team,

  My customer met a BQ76952 AFE application issue.

  When using BQ76952 AFE, setting BQ76952 to Sleep mode and configure REG1 to output 3.3V to MCU,

  the power consumption increase to 11mA (the battery package is 52V) compare to use external LDO 3.3V to REG1 with only 1mA.

  So, customer is confused about the reason of the battery package consumption increase from 1mA to 11mA when using AFE (both REG1 & REG2) LDO to supply MCU 3.3V. 

  • 0
    TI__Intellectual 2770 points

    For more details:

    Customer want to use BQ76952 Sleep mode to save power, so they use BQ76952 REG1 to provide 3.3V to MCU instead of external LDO for power saving purpose.

    When use external LDO to provide 3.3V, the MCU cost 10mA, and BQ76952 cost 1mA;

    However, when change to REG1 to provide 3.3V, the 52V battery package cost 11mA, which caused a large power consumption.

    So, why?

  • 0 in reply to Chen Yang
    TI__Guru 54715 points

    Hi Chen,

    The REG1 and REG2 are linear regulators, most of the voltage is dropped by the external BJT.  If the MCU requires 10 mA and that is provided by a switching regulator before the final LDO, the current for the switching regulator from the battery will be lower.  When the load transitions to the BQ76952 regulator circuit the current will come from the battery with no efficiency. 

  • 0 in reply to WM5295
    TI__Intellectual 2770 points

    Hi,

    it's means that customer's solution can't save power, on the contrary it would increase power consumption ?

  • 0 in reply to Chen Yang
    TI__Guru 54715 points

    Hi Chen,

    Yes, the linear regulation is not efficient.  If the system switches from an efficient power circuit to the simpler but inefficient one it will take more power.