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BQ77915: Temperature monitoring while hibernating

Cedric Corpa de la Fuente
Prodigy 30 points
Part Number: BQ77915

Hi TIers,

I would like to use the BQ77915 in my design. In my use case, I need to temperature control the battery pack while in hibernation and therefore I need to access the thermistor voltage. I would like to use just one thermistor and was thinking sharing the pin TS with my MCU (MSP430 - powered via another 3v3 supply).

Can I supply the pull-up voltage for the thermistor instead of using VTB supply? My concern is during hibernation, would it create some kind of undesired behavior if TS is supplied with a voltage while the rest of the device hibernates ?

Thank you very much.

  • 0
    TI__Guru 54715 points

    Hi Cedric,

    In hibernate the BQ77915 is basically off except the detector.  If you apply a voltage to the thermistor attached to TS and through a resistor to VTB current will leak into the part to partially power the IC.  That current will likely increase current consumption of the BQ77915 as well as alter the apparent temperature you are sensing.  If you can switch the thermistor between the 2 circuits it may be successful, but the switch resistance would need to be small to avoid altering the voltage trip of the BQ77915 and the temperature.

  • 0 in reply to WM5295
    Prodigy 30 points

    Thank you  

    I will drive the TS pin with a follower that has shutdown capability. The shutdown pin will be paired with the payload detection pin. In theory, it should work.