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BQ76940: BQ76940 output drift 70mV

elan peng17
Prodigy 190 points
Part Number: BQ76940

Hi,

  Customer used 2pcs bq76940 to develop 30cell BMS project, when the board ran about half an hour ,there will be random have 70mV drift high then the cell voltage. Reset the board, the measured value will be correct. Schematic as below. I'd like to know why this happened, how to fix this issue. thanks!

BTW, customer connect SRP & SRN for current sense, if customer revised SRN to Negative (Nearest to VSS),(Datasheet Pin Mapped SRP to Negative and SRN to Positive), Whether this issue impact the voltage measured high drift 70mV?

  • 0
    TI__Guru 54715 points

    Hi Elan,
    I don't see an issue from the schematic section shown. The description sounds like an unexpected capacitive connection. Be sure all power and input filter resistors and capacitors are in range and properly attached and that the system is operating with a low impedance source. The grounding is not clear from the schematic but appears to be attached to the bottom cell in the section shown, this should be good. Be sure the R674 is soldered well and not damaged.

    Reversing the current sense inputs should not affect the cell voltage. If the voltage on the sense pins goes significantly low or high it could push current into the part and cause abnormal operation or damage.