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BQ27532-G1: 20% variation in the StateOfCharge (REG 0x20) value

KY YUN
Prodigy 20 points
Part Number: BQ27532-G1

Tool/software:

In our current circuit design, VCC_SYS is connected to both the CE and REGIN of BQ27532, and VCC_SYS goes LOW when system power turned off.

When VCC_SYS goes LOW and then returns to HIGH, I observe up to a 20% variation in the StateOfCharge (REG 0x20) when the battery voltage is between 3.2V and 3.7V.

Other factors could be responsible, but could the transition of CE and REGIN to LOW be causing this issue? Would it be better to connect them to VBAT instead?

  • 0
    TI__Guru** 105760 points

    Hello Ky,

    Sorry for the delay, to clarify your question is related to when you are charging between 3.2V and 3.7V? Or is this variation happening anytime there is a toggle of VCC_VSYS?

    Generally if you toggle power to the gauge (CE) when the gauge wakes back up it can only use the present voltage for the SOC calculation. So if you were just charging or discharging and the toggle CE there will be variation in SOC since the battery voltage may still be relaxing up or down.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 20 points

    To clarify, the variation occurs during discharge, specifically within the range of 3.2V to 3.7V.

    In that case, do you recommend not toggling VCC_SYS or connecting CE to VBAT?

    Thank you

  • +1 in reply to KY YUN
    TI__Guru** 105760 points

    Hello Ky,

    You will get better results if you keep the gauge enabled so it can more accurately track SOC using coulomb counting + voltage instead of only voltage.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 20 points

    Thank you for the helpful information.