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BQ25302: PMID capacitor value and fuel gauge position

Ue
Genius 16285 points
Part Number: BQ25302

Hi all

My customer is working on a design with the BQ25302 and they have two questions:

For the PMID capacitor: on the simplified  application schematic on page 1 of the datasheet they find 2.2uF while the datasheet specifies 10uF on page 4. They would prefer 2.2uF to limit the inrush current when connecting to the USB, is that ok ?

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They also want to use a fuel gauge. The datasheet states to connect the BAT pin directly to the battery. That would normally be the same net as the inductor. As they are using a fuel gauge: Where should they connect BAT ? After the inductor ? or at the battery ?

Best regards

Ueli

  • +1
    TI__Mastermind 24075 points

    Hi Ueli,

       The 2.2uF on the simplified diagram is incorrect. 10uF is recommended, however under recommended operating conditions we also specify a minimum value of 5uF and a typical value of 10uF effective capacitance on the PMID pin. Thanks for bringing this to our attention. As the PMID capacitor is the input to the switching stage, I would not recommend using a lower PMID capacitance value as this is a critical component.

    The BAT pin on this device is not a power BAT rail, but rather a BAT remote sense pin. This allows the charger IC to measure as close to the real battery voltage as possible, as opposed to sensing battery voltage + voltage drop across any impedances in the path. This chargers your battery more accurately, as well as reduces charge time due to less time spent in the constant voltage (CV) phase.

  • +1
    TI__Genius 16285 points

    Hi Kedar

    Thank you for the quick reply !

    Best regards

    Ueli