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TXS0104E: Rising & Falling timing

Shu-Cheng LIN
Guru 11785 points
Part Number: TXS0104E

Hi Sirs,

Sorry to bother you.

We have use TI TXS0104E on I2C IF, 1.8V to 3.3V

We found the Rising & Falling timing is too short that over I2C specification version3.0.

Have and risk on it?

I2C V3.0

Our design:

Test Result: A (salve device) is passed, but B is fail as below:

  • 0
    Guru 269540 points
    What is "AP"? What is "B"?
    What pull-up resistors are you using on the 3.3 V side?
    Did you use the actual circuit (including all parasitic capacitances) for measuring?

    A rise time of less than one nanosecond is unlikely to be correct. Your screenshots are too small to read them, but I'd guess that the sample rate is too small.

    Too-fast edges might lead to EMI problems. To make them slower, you could add capacitors between the SDA/SCL and ground.
  • 0 in reply to Clemens Ladisch
    Guru 11785 points

    Hi Clemens,

    Thanks for your reply

    Please refer update as below.

    What is "AP"? What is "B"?

    [Ans.] AP: CPU (QCT platform), B: slave device(sensor, AMP, …etc)

     

    What pull-up resistors are you using on the 3.3 V side?

    [Ans ] The I2C power domain of slave device is 3.3V, and we don’t pull-up resistors on 3.3V side

     

    Did you use the actual circuit (including all parasitic capacitances) for measuring?

    [Ans.] Yes.

     

    Could you add capacitors between the SDA/SCL and ground.

    [Ans.] We add C-load 33pF on the SDA/SCL, it still can’t delay the rising into the spec.

     

    Could you help explain the one-shot circuit whether it will improve the rising time of I2C?

  • 0 in reply to Shu-Cheng LIN
    Guru 269540 points
    The one-short circuits short the respective signal to VCC.

    But to repeat myself: I doubt the measurements. Please zoom in on a rising edge, and show the screenshot in the full resolution.