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UCD9090-Q1: I2C bus falling time is not matched with the datasheet

Smith Chao
Prodigy 210 points
Part Number: UCD9090-Q1
Other Parts Discussed in Thread: UCD9090

Tool/software:

Hi TI Expert,

I'm using the UCD9090 in my automotive application. I’ve measured the I2C bus and found that the falling time does not match the datasheet specifications, though other parameters (hold time, setup time, and rising time) do meet the requirements.

How can I increase the falling time? Is it possible to ignore the falling time in this context?

I2C datasheet: www.nxp.com/.../UM10204.pdf

UCD9090 datasheet: 

measured waveform:

thanks

Smith

  • 0
    TI__Guru 60800 points

    Hi

    UCD9090 follows the standard I2C spec. The timing listed in the data sheet is for 400Khz. if you are using 100Khz, the rising time would be larger which is in the standard i2C spec.

    Regards

    Yihe

  • 0 in reply to yihe
    Prodigy 210 points

    Hi Yihe,

    Thanks for your reply. I’m looking to increase the "falling time" on the I2C bus while ensuring that other parameters still meet the specifications.

    Although we are running the I2C at 400 kHz and the rising time is within spec, we would like to improve the falling time.

    thanks

    Smith

  • 0 in reply to Smith Chao
    TI__Guru 60800 points

    Hi

    Your falling time is better than rising time from the waveform. What is the pull-up resistor used here?

    Regards

    Yihe