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BQ76952: BQ76952 current sense not correct

Star Xu
Genius 9645 points
Part Number: BQ76952

Hi 

The customer design with BQ76952, they use a fixed current of 20A to pass through the current sense. At first, the current value is accurate.

When the AFE chip continues to work for several hours, then charging and discharging are stopped for a few hours, and the same current is used again.

Through the shunt, the value of the AFE current acquisition is reduced, and the error will gradually increase. What is the cause of the problem?

Attached the schematic as below:

Waiting for your reply. 

Thanks

Star

  • 0
    TI__Genius 11315 points

    Hey Star,

    What is the part number and value of the shunt resistor? Also, can the customer elaborate on what the diodes are for above the SRN and SRP 100 Ohm resistors? 

    Our part uses an ADC that takes the voltage across the shunt resistor and converts it into a current value. There should be no reason for the part to gradually increase in error. Therefore I assume something might be wrong with the circuitry involving the SRP and SRN pin.

    Furthermore, I've noticed a few other small things that could lead to other problems with the schematic. If you're using thermistors, your TS1, TS2, TS3, and TS4 capacitors might be above TIs recommended value. See section 16.2 Bullet 8 of the datasheet.

    Last thing, C6 is recommended to be 22nF. The current capacitance value may cause issues with the regulators.

    Thanks,
    Caleb