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BQ76952: Can BQ76952 automatically enter shutdown mode if communication is interrupted?

L
Prodigy 220 points
Part Number: BQ76952

1.There is a scenario: The communication is interrupted abnormally, and the BQ76952 triggers the host watchdog fault. In this case, can the shutdown be enabled?

Single undervoltage Total undervoltage shutdown is not considered

2.There is another problem After the balance was turned on, I tried to turn off the balance, and waited for 1S to read the cell voltage, and found that Cell16 would still be low. Will we equalize the shutdown time very slow? I see the sampling time is around 3ms. Wait for 1S to read the voltage should be normal, right?

  • 0
    TI__Mastermind 42060 points

    Hello L,

    L said:
    1.There is a scenario: The communication is interrupted abnormally, and the BQ76952 triggers the host watchdog fault. In this case, can the shutdown be enabled?

    No, host-watchdog protection can disable the FETs, restart the LDO's or shutdown the LDO's.

    L said:
    2.There is another problem After the balance was turned on, I tried to turn off the balance, and waited for 1S to read the cell voltage, and found that Cell16 would still be low. Will we equalize the shutdown time very slow? I see the sampling time is around 3ms. Wait for 1S to read the voltage should be normal, right?

    I do not quite understand this question. Can you provide more detail?

    When reading cell voltages the part automatically turns-off balancing while the cell is being read, so there shouldn't be any measurement error during balancing. Particuarly if the balancing is off. Now, if you're seeing inacuracy during cell balancing, read Section 2.5 Voltage Measurement Accuracy During Balance of the Cell Balancing with the BQ769x2 application note.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 220 points

    So for the first question, can I understand that if the AFE communication is abnormally disconnected, this AFE cannot enter shutdown?

    The reason for the second question I consulted the manual.
    Because the equilibrium of BQ76952 involves a point of schematic design that needs special attention. The drive current of the equalizing MOSFET is drawn from the VC16 pin, and a working equalizing channel consumes ~35uA of current. For example, Cell1 and Cell4 in equilibrium at the same time will consume 70uA of current from VC16. If the RC of the VC16 pin is 100R, this will result in an error of 100R * 70uA = 7mV.

    However, if I turn off all equalization and wait 1S to read the Cell16 voltage again, should this error be eliminated? But that's not the phenomenon I tested. Have you tested this?

  • 0 in reply to L
    TI__Mastermind 42060 points

    Hello L,

    Correct, not automatically. If you want to externally SHUTDOWN the device.

    Yes correct, the error should really only occur during balancing, not out of balancing. Do you have any logs of the cell measurement before balancing, during balancing and after?

    How different is it compared with a DMM measurement?

    Can you also share your schematic?

    Best Regards,

    Luis Hernandez Salomon