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BQ78350-R2-DEVICE-FW: UTD and UTC protection

Prasanna Thengodkar1
Prodigy 110 points

Part Number: BQ78350-R2-DEVICE-FW

We are using BQ78350 which is configured to read and protect based on 3 external thermistors on cells.

As per the technical reference manual, I can select the source of cell temperature protection using CTEMP bit in the DA Configuration register. I am allowed to select this source to be either a maximum or an average of 3 thermistors.

I would like to use the minimum value of these 3 inputs for under-temperature protections in charge and discharge (UTC and UTD respectively)

And I would like to use the maximum value of these 3 inputs for over-temperature protections in charge and discharge (OTC and OTD respectively)

I would also like to disable FETs based on this protection.

I do not see any configuration which allows me to do these functions which seems odd. Kindly let me know if I am missing anything.

  • 0
    TI__Guru* 81035 points

    Hi Prasanna,

    You are correct that the two options offered are to use the average of the temperature readings or the max temperature reading to qualify temperature faults. At cold temperature, the average value is probably okay since the cell temperatures should be very close. The [OTFET] bit in the FET Options register controls whether the FETs are disabled in an over-temperature condition. There is no similar setting for under-temperature.

    According to JEITA, you would normally want to reduce charge voltage at high temperature and reduce charge current at cold temperature. 

    If you need more FET Control configuration options, you might want to look at our upcoming family of monitors - the BQ76942 and BQ76952 which offer a little more flexibility in the FET options.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 110 points

    Hello Matt,

    Thanks for the quick response. 

    We do not use a smart charger for our battery pack. For temperatures < 0°C, I would like to open the charge FET.

    However, we do have FET control though our MCU which I can use for this case. But I would have liked to use TI device for all protections.

    Thanks and regards,

    Prasanna