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Permanent AFE Communications failure using BQ20Z70-V110 and BQ29330

Andrew Fomushkin
Prodigy 30 points
Other Parts Discussed in Thread: BQ20Z70, BQ29330

I'm using BQ20Z70-V110 and BQ29330.

I have a problem: when charging close to end, Permanent Failure happens with PFStatus 0x0100 i.e. Permanent AFE Communications failure according to SLUU250A, what is this ? I can't find a description of that failure.

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  • 0
    TI__Expert 6470 points

    Andrew,

    There are two possible causes of for the AFE communication failure you are seeing:

    First is when the bq20z70 detects too many errors in I2C communication with the bq29330. This could be caused by a bad device, or even bad soldering which fails continuously, or at certain temperatures. If this problem is just occuring in a single unit, I suggest changing the IC and checking the soldering.

    Second, the AFE_C flag is raised if there are too many resets occuring which prevents proper initialization of the AFE voltage measurements. The bq20z70 uses its internal ADC to measure initial AFE (bq29330) offsets and gain values on every reset. The quality of these readings are critical to the accuracy of the voltage as displayed by Voltage and Cell Voltage(All). Poor initial offset and gain readings can alter the voltage displayed, and it can take several minutes to reacquire accurate readings due to an internal slow responding digital filter in the bq20z70 firmware. With the importance of the quality of these initial readings, the bq20z70 takes 2 successive readings of these offsets and gain values, and compare them. If the comparison fails to meet specified criteria then it retries several times before it forces an AFE_C PF Flag. This situation is normally caused by poor PCB layouts and noisy environments.