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BQ32000: RTC Time Inconsitant & Resetting

Roland Melad
Intellectual 1185 points

Part Number: BQ32000

We are using BQ32000DR in our custom design board. We have connected Super Capacitor as VBAT supply. We are facing below issues while testing the RTC during the power cycle.

Issue No:1 - RTC Time drift.
There is time drift while testing the RTC after couple of power cycle. This delay is inconsistent. Some time delay is 5 sec, some time delay is 10 minutes... so and so. Other-words, There is random delay in the time while reading the RTC after couple of power cycle.

Issue No:2 - RTC Time Reset
There is RTC time reset is occurring after couple of power cycle. After couple of power cycle, the RTC time is reset to old factory set time.

  • 0
    TI__Guru** 121260 points

    Hi Roland,

    My colleague is OOO till next week, we will get back to you later.

  • 0 in reply to Noel Fung
    TI__Genius 16845 points

    Do you power cycle VCC while VBack is still powered? Or is Vback power cycled as well?

    There is a delay of 1second until the time-keeping register are updated after VCC is restored when operating from Vback. However, 10 minutes would be much longer than expected.

    What is the Vback voltage when the time is reset?

    How long is the RTC powered off when you get the measurement delay?

    Kind regards,
    Lane

  • 0 in reply to Lane Boyd
    Intellectual 835 points

    Dear Lane,

    We are doing the multiple power cycling test (cut the VCC and restore it) continuously within 1 sec as mentioned in the diagram below. Below image is 1 power cycle diagram. I,e 1 sec is the time taken between each power cycle. When we did such multiple power cycling tests, we found that there is drift in the RTC time. Example, when we did power cycling 10 times (each power cycling time less than 1 second), then we found 10 second drift in the time.

  • 0 in reply to Mohammed Azlum
    TI__Genius 16845 points

    Thanks for the info. The time-keeping registers update once per second, and can take up to one second to update after supply switchover. This explains why it is possible to observe 1 second delay after each supply switchover.

    Kind regards,
    Lane