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BQ40Z50-R1: Cycle count value corruption

Eddie Koh
Genius 10635 points
Part Number: BQ40Z50-R1

Customer is using BQ40Z50-R1. The cycle count value was observed to be corrupted.

Use case:

- Fuel gauge IC is not sealed.  However, the device host communicating with the fuel gauge IC does read commands to the fuel gauge including Cycle Count.

 

During evaluation of the battery and device:

- It was observed that cycle count jumped from 0 to 65535 (FFFF).

- Customer rewrote the cycle count to a low value and repeated the inserting and removing of the battery. Outcome: cycle count jumped to 64794 (FD1A).

- Customer tried to rewrite the cycle count again to a lower value and repeated inserting and removing of battery, turning on/off the device but was not able to reproduce the issue again.

 

Questions:

1. Is there a possibility during repeated insert and removal of battery pack, the communication was still ongoing?

2. When the battery is removed, would accidental write occurs?

3. Is there also a possibility of noise from the environment affecting communication and doing an accidental write?

  • 0
    TI__Intellectual 2146 points

    HI Eddie,

    1. If the SMBus lines were disconnected, then it's possible that the value got corrupted while trying to read.

    2. Again if the SMBus lines were disconnected as well, then this is possible.

    3. That could be a possibility, also the likelihood of that occuring depends on how protected the physical bus lines are. Depending on the length of the bus lines, the signal edges could also degrade to a point where data corruption occurs.