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BQ76930 BQ76940 电池包库存1个月后AFE采样引脚漏电

衣者
Prodigy 91 points
Other Parts Discussed in Thread: BQ76940, BQ76930

BQ76930 BQ76940 分别用于10串、13串的两个项目，量产后发现电池包库存一段时间后，BQ76930的第10串，BQ76940的10串12串和13串电池漏电，分析发现AFE的相邻的采样引脚存在漏电，可以确认电池包入库时AFE是没有漏电问题的（如果入库时AFE的采样引脚就存在漏电，1K的采样滤波电阻就会存在压差，上位机可以检测出来），不良的保护板断电后静置1小时，再重新上电，多数情况下之前AFE漏电的故障会消失，但是静置工作一段时间后（可能是10分钟，也可能是1天），故障又会复现，漏电电流呈现逐渐变大的情况，1K的采样滤波电阻上出现电压，采样电压会小于实际电池的电压，AFE输出的电压和AFE采样引脚的电压相同（AFE内部AD采样还是正常的），目前电压采样端口没有加TVS保护二极管，想知道AFE具体的损坏环节，有没有人也遇到过这样的问题，怎么解决的？谢谢！

  • 0
    TI__Guru*** 130456 points
    您好，您的电路方便发过来看一下，发现有漏电流的板子和正常的板子建议做一下对比看一下哪里的问题。
  • 0 回复 衣者
    TI__Guru*** 130456 points

    您好

    You can measure the leakage as a voltage across the resistors, and the part can measure it as well.  The challenge now is to find out if the leakage is in:

    • Contamination on the board assembly
    • The IC
    • The capacitor
    • The PC board itself.

    We have seen all of these cases with the BQ769x0.  Similar to removing power, heating the board to desolder parts will often clear the issue also, either temporarily or permanently. You might try to reflow the part and see if it returns, or swap parts between good and bad boards to see if the issue stays with the part or board.

    Creating a table of the voltage across each Rf and Rc filter resistor can be helpful to see where the current is going. If RVC10 has current in and RVC9 has current out, leakage could be in the IC, between the pins, in the board, or in the cap.  If RVC10 has leakage in and RVC5X has current out, it could be the IC or in the board, leakage in a cap is unlikely since none connect directly, and pins are separated. 

    You may be able to lift an IC lead without heating significantly, but often it may be a destructive test cutting IC pins or board traces to see when the leakage stops.