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BQ76952: Floating Unused BREG Pin Reduces Quiescent Current

Zaya Lazar
Prodigy 40 points
Part Number: BQ76952

Tool/software:

Hello,

We measured that the BQ76952 IC draws about 7mA of quiescent current in our design (pictured below). Interestingly, when we float the BREG pin (by removing R96), the quiescent current drops to about 2mA. However, the datasheet recommends grounding the BREG pin if both REGIN and BREG are unused.

Do you have any insights on why this occurs, and is there any risk associated with floating the BREG pin if it is unused?

Best,

Zaya

  • +1
    TI__Expert 7060 points

    Hello Zaya,

    It looks you are using specifically the BQ7695202 device that has the REG1 LDO enabled by default. Section 5 Device Comparison Table in the BQ76952 Datasheet shows this.

    Even if BREG and REGIN are not being used, BREG under short-circuit conditions can draw approximately 3.33mA or more as shown in Section 7.11 REG0 Pre-regulator of the datasheet. This is because, REG0 is being used to generate what's needed for REG1. This is explained in Section 12.3 LDOs of the datasheet. 

    Since you aren't using BREG/REG1, you should disable the pre-regulator. Further details on how to do it can be found in Section 6.3.1 Preregulator Control in the TRM.

    Best Regards,
    Alexis