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BQ76PL455A: Cell voltage sensing inaccurate

Xiao Cao
Prodigy 10 points

Part Number: BQ76PL455A

Hello, 

We use two BQ76PL455A chips in our BMS boards for 28S battery configuration. We found the cell voltage reading is consistently lower than actual cell voltage for all cells(about 30 ~ 50 mV lower for each cell). This is way beyond the spec in the datasheet. After we use over-sampling in BMS IC (32 average), the results are better. However, this increased the sampling time significantly. I wonder what could cause the lower voltage reading for all cells. Thanks.  

  • 0
    TI__Genius 9531 points

    Hello,

    Thanks for your question. Do you have balancing function enabled during your test? One good thing to check is to make sure that the voltage at the VSENSE input pins (preferably directly at the pins) is not oscillating so you could connect an oscilloscope to measure the signal of  VSENSE pin where you see the issue and see if it's moving ~30 to 50mV. Another thing to try is to use the recommended settings in section 7.3.3.3 "Recommended Sample Periods" of the device datasheet.

    Best regards,

    Leslie