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BQ76952: Separate BAT- and PACK- Planes

Kevin Knicker
Expert 1101 points
Part Number: BQ76952

Tool/software:

Dear TI Support,


What are the effects of not having a separate BAT- ground and a PACK- Ground?

I know they are supposed to be separate planes from various TI resources, but I am reviewing a design where PACK- is not a separate plane on the output side.

I have the sense resistor portion of the reference schematic for the bq76952 shown, along with the sense resistor portion of the design I'm reviewing.

With cells connected to the circuit as shown on the right, I am seeing a -8mA current draw through the sense resistor with no load attached.

My thought is that because there is not a separate plane on the output side (PGND), something is drawing current from the cells (perhaps some other circuitry), and it is seen as a load by the sense resistor.

Does that seem like it would be expected behavior?

Regards,

Kevin

  • +1
    TI__Genius 17915 points

    Hello Kevin,

    That is possible. We usually recommend having VSS connected through a net tie to BAT- to separate the high-current path of the battery current, from the low current path of the IC ground. This helps keep ESD and high currents away from sensitive IC components.

    Best Regards,
    Alexis