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UCD9090A: UCD9090A ISSUE

Dane Zhang
Expert 7625 points
Part Number: UCD9090A 
Hi team,

There is currently an abnormal UCD9090A on a board, the symptoms are as follows:
1. The high level of I2C (SCL/SDA) (3.3V pull-up, pull-up resistance 1.5k) is abnormal, the voltage measured at the arrow in the figure (49.9R remote) is 1.921V, and the voltage across 49.9R is 45mV, after disconnecting the 49.9R resistor, the voltage at the arrow returns to the normal 3.3V voltage. There should be a 45mV/49.9R=0.9mA sink current inside, and a voltage drop is generated at the 1.5k ends of the pull-up.
2. BPCAP (pin 35) voltage is 1.11V, normal chip is 1.764V;
  • 0
    TI__Guru 65610 points

    Hello

    If the BPCap only has 1.2V, the device is not under normal mode. Do you know what had been done on this particular device?

    Regards

    Yihe

  • 0 in reply to yihe
    TI__Expert 7625 points

    Hi yihe,

    This board is newly made recently. It is found that the FPGA is abnormally loaded after power-on, and the UCD9090A cannot be scanned after connecting the USB adapter.
    1. Measure the abnormal 1.921V of the I2C voltage, and judge the second UCD9090A (a total of 4 UCD9090A, sharing one set of I2C) through the voltage drop across the I2C series resistance, and disconnect the series resistance on the SCL/SDA, which can scan To the other three UCD9090A, the BPCAP voltage is 0.945V;
    2. Re-solder the SCL/SDA series resistor and re-solder UCD9090A. The I2C voltage is still abnormal at 1.921V and the BPCAP voltage is 1.11V.

    do you have any advice for this issue?

  • 0 in reply to Dane Zhang
    TI__Guru 65610 points

    Hi Dane

    Could you compare the IO impedance of suspected IC with the normal IC to see any difference? It feels that the I2C was damaged somehow.

    Regards

    Yihe

  • 0 in reply to yihe
    TI__Expert 7625 points

    Hi Yihe,


    Disconnect the 49.9R series resistance on I2C, and the measured impedance information is as follows:

      NORMAL IC ISSUE IC
    SCL 2.078 MΩ 3.778 MΩ
    SDA 2.084 MΩ 3.116 MΩ


    If the I2C part is damaged, can you help confirm the cause of the damage?

    In addition, will the I2C part damage cause abnormal voltage at the BPCAP pin?

  • 0 in reply to Dane Zhang
    TI__Guru 65610 points

    Hello

    If the BPCap does not have a good voltage around 1.8V, it means device is not functional which may cause problem on the I2C.

    It could be a EOS damage on the IOs resulting in damage on the IC(Bad BPCap voltage). It is hard to tell unless a FA.

    That's why we want to understand what happened and how many cases does the customer see?

    Regards

    Yihe 

  • 0 in reply to yihe
    TI__Guru 65610 points

    Hi Dane

    This issue has been addressed and I will close this post

    Thanks

    yihe