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UCD9090: I2C Address setting

mmWaver
Prodigy 200 points
Part Number: UCD9090

Hello,

On our PCB when we use 41.2k 1% resistor on both address pins to set UCD9090 address to 0x41, sometimes the UCD9090 will not respond to this address about 5-seconds after power up. But it will respond afterwards. We are not seeing this issue when we used 90.9k to set the device to 0x68, that is, the device always responds shortly after power up.

The circuit board looks clean with no flux residue so I am not suspecting leakage current causing the issue. What else should we be looking into in order to root-cause this problem?

Thanks!

  • 0
    TI__Guru 60800 points

    Hi

    Could you please help on below questions?

    1. what's the pull-up resistor used for i2c?

    2. do you have other i2c slaves on the same bus? will they happen to have the same address?

    3. during the 5-seconds, was the correct address NACKED? do you have a waveform?

    4. could you use USB-TO-GPIO Dongle + Fusion GUI to scan the i2c bus during the first 5 seconds?

    Regards

    Yihe

  • 0 in reply to yihe
    Prodigy 200 points
    Hello Yihe,
    Thank you for your reply. I think we found the potential issue. There were glitches on the clock and data lines during power up, which probably caused UCD9090 to think there's start of transmission but no stop, so that when its real I2C address is sent, the UCD9090 does not recognize it.
    We are working on ways to resolve it. Please let us know if you would recommend an easy solution.
    Thank you so much for your help,
    Paul
  • 0 in reply to mmWaver
    TI__Guru 60800 points
    Hi Paul
    Thank you for the updates. please let's know the results.
    Regards
    Yihe
  • 0 in reply to yihe
    Prodigy 200 points

    Thank you Yihe for your help. This resolves our issue.