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BQ76930EVM: BQ76930 Pack Current

Part Number: BQ76930EVM

hi everybody

I have BQ76930EVM and I connected to the IC trough I2C and i am getting the cell voltages very well.

the problem happens during reading current. the only registers that are contributed to current are CC_HI(0x32) and CC_LO(0x33) which are Coulomb counting value.

how can I convert this value to Pack charging or discharging current ??

there is a formula in the datasheet that mentions this: CC Reading (in µV) = [16-bit 2’s Complement Value] × (8.44 µV/LSB)
but it does not seem to work for my purpose.

thanks in advance 

M.A.

  • Hi Mohamad,
    There are 2 setup items required for the reading, enabling the CC in register 5, and setting register B to 0x19 for low CC offset. After the CC completes its integrating conversion (250ms) it will set CC_READY in the status and a value will be available. Before the completion there will be no value (after start). Since you don't know the internal timeline of the part, once you write CC_EN for example, it may be almost 500 ms before a value is available if the write just missed the start of the interval.
    If you apply a constant 1A current to a 1 mOhm sense resistor such as on the EVM, the device pins should get 1 mV. The conversion should give 1 mV/8.44uV/LSB = ~118 LSBs. If the current was not a constant, the CC will integrate the current and some other value will be present. Charge current is positive, discharge current is negative.
    Working the other way, if you have a reading of 0x0111, it is positive. This is (273 LSBs x .00844mV/LSB) = 2.3 mV at the input pins. Divide by the sense resistor, (2.3 mV)/(1mOhm) = 2.3 A. Since it is positive it is a charge current. If the number is negative take the 2's complement to find the LSBs.
    Hope this helps.