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BQ3200 time keeping registers

Amjad EL HILALI
Intellectual 1915 points

Hello team,

Concerning the time keeping registers of the BQ3200. It is said on certain registers description that it can take up to 1 second to be updated after the RTC switches from backup power supply to main supply. However it is not said for the OF and STOP bits. Does it apply also? 

Also it is said on page 13 of datasheet "When OF is 1, the oscillator fail detect circuit has detected at least our consecutive dropped pulses." What does it means exactly?

Best regards,

Amjad

  • 0
    TI__Mastermind 28590 points
    Hello,
    I've notified an engineer to respond.
  • 0 in reply to Timothy T
    TI__Guru** 114905 points
    Hi Amjad,

    Please note section 7.4 of the datasheet:

    When the device switches from the main power supply to backup supply, the Time keeping register Registers [0-9] cannot be accessed via the I2C. The access to these registers are only when VCC > Vref.

    The Time keeping registers can take up to 1 second to update after the device switches from backup power supply to main power supply.

    Since the OF and STOP bits reside in the time keeping register, the statement above apply.

    The OF fail is monitoring the OSC inputs to confirm the oscillator is operating. If the oscillator stops or remains in one state for too long, the OF fail flag is set.
  • 0 in reply to Rick Duncan
    TI__Intellectual 1915 points

    thanks for the response,

    Customer has checked the delay between power on and RTC register reading, they have 1,4 seconds which is sufficient  to have valid datas. If they reduce the delay to 240ms that works also.
    During investigations, they have seen a strange behaviour :


    The 2 first configurations are OK, we get OF=1 when either Vbat shuts down during power off or Crystal is frozen at power up.
    The last one is strange because we get OF=0 when Vbat shuts down during power off and crystal is frozen at power up.

    Can you please give an interpretation for this?

    best regards,

    Amjad