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BQ32000: Clock & timing forum

Part Number: BQ32000

Hi teams,

We have been applying the BQ32000 to our products.
In some products manufactured last month, when the power was turned off, there was a problem of RTC reset.
As a result of the analysis, it was found that the OSC waveform level of the defective product was lower than that of the normal product.
The results of various environmental tests on defective products did not return to normal.
When the 'STOP' bit of SECONDS Reg. is changed to '1', it is confirmed that the OSC operation stops, and the IC seems to operate normally.
OSC operates when'STOP' bit of SECONDS Reg. is changed to '0'. However, the defect phenomenon remains the same.
However, when the auxiliary battery (CR2032) is removed and attached, it operates normally.
After normal operation, the defect phenomenon is not reproduced even in various tests.
what can be the reason for this phenomenon

Regards,

  • What is the amplitude of the OSC waveform on a good device?

    Is the device powered from VCC when the battery is removed and attached?

    What exactly is the problem observed with the RTC reset? Is there an issue with the time reading?

    Kind regards,
    Lane

  • What is the amplitude of the OSC waveform on a good device?

    Good- 340mV, NG- 110mV

    Please refer to waveform below.

    Is the device powered from VCC when the battery is removed and attached?

    No. it isn't.

    We can't do that test because have no NG sample.

    What exactly is the problem observed with the RTC reset? Is there an issue with the time reading?

    MCU couldn't read the time from the RTC, because of 'OF' flag. So every time the system was turned on, MCU showed the initialized time.

    Regards,

  • Thanks for the clarification. I understand the problem better.

    On the defective systems, does the oscillator have 340mV swing before being turned off?

    Is the same battery reattached? Or is it a new battery, with full charge?

    Can you share the schematic and datasheet for the crystal?

    Kind regards,
    Lane

  • On the defective systems, does the oscillator have 340mV swing before being turned off?

    -> It always maintained 110mV swing with or without VCC.

    Is the same battery reattached? Or is it a new battery, with full charge?

    -> Same battery right. 

    Can you share the schematic and datasheet for the crystal?

    -> Please refer to the images below.

    Regards,

  • I was missing the datasheet of crystal (CS-306), so I upload the image again.

  • My apologies for the delay in responding here. I'm not certain what is causing this issue. Did you have any updates from your debug?

    One thing to be aware of is that the device expects a 1ms pulse minimum on VCC after reconnecting the backup supply. This is detailed in datasheet section 8.2.2.3 . When you reconnect the battery and the defect behavior goes away, please try to apply VCC. This should reduce the current consumption and I'm interested if it affects the device behavior. Also, what is the battery voltage?

    For the schematic, C502 and C503 can be depopulated, since the load capacitance of the crystal already matches the crystal oscillator.

    Please send us an email at cts_rtc_nt_flex@list.ti.com and we can offer additional support.

    Kind regards,
    Lane