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BQ76930: DEVICE_XREADY is set to 1 in the cells balance state

BobLi
Prodigy 30 points
Part Number: BQ76930

hi,

we're using the bq76930  for a 20 cells battery system,  now we meet some problems about the DEVICE_XREADY and need some help.

the system can working normal in the state without balance. and there is some abnormal event occurs when we do the cells balance.

in the charging time, we will set the cells balance on, some minutes later , DEVICE_XREADY is set to 1.  if we stop the cells balance, and clear the DEVICE_XREADY,  it will recover the normal state.

we do the balance at 2 cells Intervals, for example, the 2nd is balancing on, than the 3rd, 4th is off, and 5th is on(if the 5th cell voltage meet the balance voltage).

thank you.

  • 0
    TI__Expert 7455 points

    Hi,

    XREADY will trigger when 5 of the 8 communications between cell groups internal to the part are corrupt in a 1 second interval.  The part considers the reported result unreliable in this condition and turns off FET outputs. Some common causes:

    1. Missing power on upper groups such as droop as you indicate causing reset of the group

    2. Broken or missing power connection

    3. Shorted CAPn capacitor

    4. TSn having trapped voltage at boot due to missing pull down

    5. Pull down of TSn below its reference (abs max violation)

    6. Large noise on power pins

    7. Some customers have reported XREADY in high field strength environments, it is not know if the entry is through the power pins or TSn to a remote thermistor or other.  Filtering and shielding are the expected solutions.