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BQ76952: Current sampling frequency for charge integration

Annie Liu
Genius 10295 points
Part Number: BQ76952

Hi Team,

The customer learned that the CC1 filter is recommended for charge integration. It outputs a value every 250ms, which is converted to a frequency of 4Hz. When cooperating with the inverter to output 220Vac/50Hz for testing, he found that the current waveform of the battery pack would follow the frequency of the AC output. So, the sampling frequency of the current cannot satisfy Nyquist's theorem, that is, the sampling frequency needs to be twice the signal frequency.

The specification sheet states that integration through charges can be provided in the form of 64 bit values using the 0x0076 DASTATUS6() subcommand. What sampling frequency was used to obtain this charge integral?

Best regards,

Annie Liu

  • 0
    TI__Mastermind 33330 points

    Hello Annie,

    For coulomb counting/charge accumulation, CC1 is used. Which integrates the current over the 250-ms period. This is not a sample taken every 250-ms, it is actually the integrated current over the 250-ms (so averaging the current). If there's an AC signal, I'd imagine it may filter it out.

    CC2 or CC3 can be used instead of CC1, if desired. CC2 provides a current measurement with an integration period of 3-ms (So there's a new current measurement every 3-ms).

    CC3 can average out a certain number of CC2 measurements (up-to 255 CC2 measurements averaged out).

    The accumulated charge can be read from the DASTATUS6(), which has the accumulated charge over a period of time that is also reported in there. There is a more detailed explanation in Section 4.3 Coulomb Counter and Digital Filters of the Technical Reference Manual (See image below):

    Best Regards,

    Luis Hernandez Salomon