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BQ20Z655-R1: What will happens if we choose the sense resistor is outside of 5-mΩ to 20-mΩ

Billy Xu
Intellectual 490 points
Part Number: BQ20Z655-R1

Hello Sir,

The bq20z655-R1 datasheet  recommended to use  5-mΩ to 20-mΩ typical sense resistor on page 14.

The original text is as follows ,

The bq20z655-R1 uses the SRP and SRN inputs to measure and calculate the battery charge and discharge
current using a 5-mΩ to 20-mΩ typical sense resistor.


In our battery pack design , we choose 2mΩ for sensen resistor . I want to kown , What will happens if we choose the sense resistor is outside of  5-mΩ to 20-mΩ ? 

When our system power on ,the inrush current is over 50A .   So we need choose the lower sense resistor than the 5 mΩ for bigger current sense.

Thanks!

Billy

  • 0
    TI__Mastermind 24870 points

    Hello Billy,

    It is not recommended, we have seen ghost current where the board has no current, but the gauge is integrating current for sense resistors which are too small.

    For larger sense resistors, you may see voltage saturation and higher I^2 R heating to cause current measurement inaccuracies.