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BQ76940 Columb Counter Error

Uranus Leou
Prodigy 40 points

We use the BQ7694001 for AFE.
The coulomb counter is read in the range of FFF8 ~ FFFC.
We have measured values the regout level is 2.45V.
And when we change the Loading the coulomb counter still keep in the range of FFF8 ~ FFFC.

  • 0
    TI__Guru 54715 points

    Check that the CC is enabled, it has a separate control bit from the voltage ADC, see CC_EN, bit 6 in the SYS_CTRL2 (0x05) register.  The bit is in the same register as the FET control signals, be sure it is not being turned off accidentally when the FETs are controlled.  If you are using the one shot measurement instead of continuous enable, be sure the CC_READY status is being cleared before setting the one shot enable.

    If you have 3.87 mV at the sense filter, this should be about 459 counts.  Check that the connections are really made between the filter and the SRP and SRN pins.  Be sure the pins are soldered to the pads.

    R33 and R35 are shown as 0 ohms in the figure above.  The recommended filter resistance (RFILT in the datasheet) is 100 ohms minimum.  Be sure the part has not been damaged by some transient.