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BQ32002: Cannot write to register

Chase Jeong
Genius 4670 points
Part Number: BQ32002

Hello TI experts,

I asked about the weird operation of BQ32002 ;

https://e2e.ti.com/support/clock-and-timing/f/clock-timing-forum/970909/bq32002-clock-information-reset-when-the-system-is-reset/3593851?tisearch=e2e-sitesearch&keymatch=bq32002#3593851

i tested more about this. the result is, i cannot write to register on fault device.

1. the write on normal device, and read it;

- i write 19th may, 2001, 09:00  =>  00 00 00 07 19 05 01 80 90 8a

- i write 19th may, 1988, 11:12  =>  00 12 02 05 19 05 84 80 90 8a (i think it is normal operation.)

2. the write on fault device, and read it;

- i write 19th may, 2001, 09:00  =>  00 7d 3f 05 1f 1f ef 80 90 aa

- i write 19th may, 1988, 11:12  =>  00 7d 3f 05 1f 1f ef 80 90 aa  (the result was same even i write different value.)

furthermore, this value of register is exactly same as the value that right after the device is booted. and it never changed even i enter any value.

can you give me any advice for this situation?

Best regards,

Chase

  • 0
    TI__Genius 16845 points

    Hi Chase,

    It is not clear what may be causing the I2C issues on faulty devices. What is the I2C clock frequency? What voltage is measured at VCC and Vback? Are the values of the registers right after boot the same for a good device and a faulty device?

    Please confirm that the I2C timing requirements provided in datasheet section 6.6 are met. You can try changing to 100kHz if you are operating at 400kHz for fast mode. 

    Kind regards,
    Lane

  • 0 in reply to Lane Boyd
    Genius 4670 points

    Hi Lane,

    Thank you for your reply.

    actually i did A-B-A swap test on the same PCB, so other conditions are exactly the same.

    - I2C clock frequency : i have to check it.

    - VCC : 3.3V

    - Vback : 3.0V

    - the values of the registers are different right after boot. on the first boot, i think some garbage values are written on it, it wrote well and after first write on the good device, it remains after reboot. but on faulty device, it does not change at all even i try to write new value or after reboot the device. just remain the same garbage values on first boot.

    and I have one question, what is the difference between 100KHz operation and 400KHz operation? is it related to the stability of I2C communication?

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Genius 16845 points

    Hi Chase,

    Thanks for the information. In addition to the ABA swap, you might check if the suspect component can communicate on another board.

    Can you check the I2C waveforms and confirm whether the device is ACKing on I2C write? If the device provides an ACK, then the write operation was successful, but the registers were not updated.

    My recommendation is to confirm that the I2C meets the timing requirements specified in table 6.6 . If the timing does not meet the specification, try to bring the timing into spec. There are no significant differences between 100kHz and 400kHz besides the specifications in table 6.6 .

    Be sure to handle the IC properly during installation to avoid accidental damage. That may reduce the amount of failures that can be caused due to electrical overstress.

    Unfortunately I do not have other suggestions to recommend.

    Kind regards,
    Lane