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RTC time compensation not working on TPS65930 PMU

Ouri Poupko
Prodigy 10 points
Other Parts Discussed in Thread: TPS65930

Hello,

We are trying to use the RTC time compensation feature on the TPS65930, as described in http://focus.ti.com/lit/an/swca024/swca024.pdf. We write a compensation value to the RTC_COMP_REG registers. We use 0x7530 for our test. Our systems run slow by about 6 to 8 seconds per day. Using the above value, we expect them to run about 16 seconds faster per day.

We also write 0x5 to RTC_CTRL_REG. We then read the registers back to make sure we wrote them successfully.

Some of our systems behave as expected, yet some other boards don't show any change, and keep their usual delay. All boards are of the same HW.

Is there any other register or other factor that is relevant to the compensation mechanism that we are overlooking?
Can anyone advise how can we debug this issue to understand why some of the boards fail to compensate the clock?

Any advice or help will be appreciated,
Thanks,
Ouri.

  • 0
    TI__Expert 6090 points

    Hi ,This is the only register you need to write. Each board will have differnt dealy and need to be compensated accordingly.The clk needs to be compared with very accurate clk to measure the differnce as described in the docuement before applying any compensation.

    Thanks,

    Puneet