• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 383 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ35100: Time Resolution and accuracy of BQ35100

mahesh keste2
Prodigy 40 points
Part Number: BQ35100

I have a basic question about the coulomb counter in the BQ35100.
I'd like to use this device to measure the charge accumulation of a primary LiSOCl2 battery.
This battery is powering our device that has a very complex current consumption profile.
The device can draw from 4uA to 400mA. It may draw a few seconds or a few milliseconds. The current burst is very short duration sometimes up to 20ms only.

I'm uncertain if the coulomb counter in the BQ35100 has adequate time resolution (granularity?)
to record these short bursts. The datasheet uses the term "continuously" when describing the characteristic of the counter but I presume there is some minimum duration that the device can sense.

Could you explain if (how?) the BQ35100 captures these current bursts?

What will be the accuracy for the current 4uA.

I didn't found exact information related to time resolution and accuracy in datasheet.

Thanks,

Mahesh Keste

  • 0
    TI__Guru** 105590 points

    Hello Mahesh,

    If you are looking to use the bq35100 in accumulator mode, it is best the pulse you're trying to capture is more than 32ms, the gauge uses delta-sigma ADCs to do charge accumulation, and the sample time is every 8ms, so this ensures we get a few current readings.

    You most likely will not get enough voltage on the SRN and SRP pins to measure 4uA, accumulator mode is designed to measure short bursts.

    Sincerely,

    Wyatt Keller

     

  • 0 in reply to Wyatt Keller
    Prodigy 40 points

    Thanks,

    Sample time is every 8ms that means it will measure every 8ms but the update rate in the accumulator is per second correct?

    So for a higher pulse width like 100ms and above but less than 200ms this will be accurate?

    What minimum current it can be measured if 4uA is not possible?

     

  • 0 in reply to mahesh keste2
    TI__Guru** 105590 points

    Hello Mahesh,

    Anything over 36ms should be fine. The delta sigma design is best for charge accumulation because it is based on over sampling. It doesn't really matter if it's only once per second because it still captures the charge passed.

    You will need to check the spec on the DS for the resolution on the SRN and SRP pins, it will be based on how big your sense resistor is and your min and max current.

    Sincerely,

    Wyatt Keller