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Original question:

BQ35100: BQ35100 Current sampling rate Query

BQ35100: Current period sampling in ACCUMULATOR (ACC) Mode

Yohann Duranceau
Prodigy 20 points
Part Number: BQ35100

Hi,

I am currently trying to do Coulomb accumulation (ACC) with the BQ35100.
I am looking for monitoring short events (10ms or less), so I wanted to know what period is used for sampling the current.

Can't find time resolution for ACC mode in the datasheet, but I found these topics: 
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/657246/bq35100-bq35100-current-sampling-rate-query?tisearch=e2e-sitesearch&keymatch=BQ35100
and
https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/971444/bq35100-time-resolution-and-accuracy-of-bq35100

According to the first topic, the current sampling rate is 65KHz, but seems in reality to be about 125Hz as the period sampling is 8ms according to the second topic.

So at the end, is the current sampling period about 8ms ?

King regards,

Yohann

  • +1
    TI__Guru** 105770 points

    Hello Yohann,

    For delta sigma ADCs the operation principle is based on over sampling. One conversion may be available after 8ms as the second post indicates but there were thousands of "samples" to get that single conversion. The ADC sampling rate is 65kHz, but the conversion time varies depending on the firmware and which ADC is being used (CC or voltage ADC).

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 20 points

    Hi,

    Thank you for the response.

    So if I correctly understand, in ACC mode, the conversion time is about 0.5 second for Coulomb Counter due to a 65KHz over sampling frequency and a 15 bits precision.

    I guess the 8 ms conversion time only concern the End-of-service mode because of a 2MHz over sampling frequency (I suppose because of the higher consumption 315µA)

    King regards,

    Yohann

  • 0 in reply to Yohann Duranceau
    TI__Guru** 105770 points

    Hello Yohann

    All ADCs use the LFO frequency, 2MHz is for the CPU. Voltage uses a shorter conversion time with slightly low resolution. The datasheet specification for our ADCs are very conservative for performance.

    Sincerely,

    Wyatt Keller