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BQ76952: Equalization loop fault detection

Colin Chen
Expert 1155 points

Part Number: BQ76952

We would like to inquire whether the BQ76952 chip has the function of equalizing loop fault detection, and can the equalization loop detection be realized through hardware or software?Refer to the TI manual for hardware designCell Balancing With BQ769x2 Battery Monitors (Rev. A) (ti.com), as shown below

  • 0
    TI__Mastermind 27321 points

    Hello Chen,

    The device incorporates a voltage-based balancing algorithm which can optionally balance cells autonomously without requiring any interaction with a host processor. Or if preferred, balancing can be entirely controlled manually from a host processor.

    When using the autonomous feature, the device will balance the selected cells down to the lowest cell voltage.

    Colin Chen said:
    can the equalization loop detection be realized through hardware or software?

    If autonomous balancing is used, the device will automatically detect when the selected cells have been balanced down to the lowest cell. On the other hand, if host controlled is used, then the user will have to monitor the cell voltages and stop cell balancing manually. 

    Note: Figure 2-2 above shows external balancing circuitry. This circuitry does not come with the BQ76952. This is just a reference to help customers create their own external balancing circuit. External balancing circuits are not always needed, only for applications where higher balancing current is needed (this is explained in the cell balancing app note).

    Regards,
    Jose Couso 

  • 0 in reply to Jose Couso
    Expert 1155 points

    I am adding an external NMOS to increase the equalization current, if the external MOS is shorted or the equalization resistor is shorted, this should cause equalization failure, is there a way to detect these fault conditions?

  • 0 in reply to Colin Chen
    TI__Mastermind 27321 points

    Hello Chen,

    It is unlikely that both the FET and the balance resistor short at the same time. If this happens, the device will immediately detect under voltage and trigger the protection.

    It is more likely for the FET to damage if care is not taken when selecting the NMOS. In this case, the part will slowly detect under voltage. 

    Note: Current rating of MOSFET should be three times higher the balancing current.

    Regards,
    Jose Couso