• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 33 subscribers
  • Views 609 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PCA9545A: PCA9545A output random I2C command after power on

Luke Sun
Intellectual 1830 points
Part Number: PCA9545A

Hi team,

My customer found that PCA9545A will output some random I2C command during power on, while the master didn't send any command.

Do you have any idea why it happened?

Thank you!

  • 0
    TI__Mastermind 21125 points
    Hello Luke,
    We would need to get some waveforms and block level schematics to make sure the part is setup properly. I can't foresee any reason why that would happen.
    -Francis Houde
  • 0 in reply to fhoude
    TI__Intellectual 1830 points

    Hi Francis,

    Attached is the schematic and the waveform.

    Blue line is clk, Green line is data.

    Could you find any clues on what have happened?

    Thank you

  • 0 in reply to Luke Sun
    TI__Genius 16450 points

    Two observations:

    1) Your resolution on your waveform is very low. Can you obtain a higher resolution (time scale) waveform? It's difficult to see the waveform accurately.

    2) The PCA9545A itself does not have any ability to pull-down on the clock line. It physically does not have any pull-down driver, so it is not possible that the PCA9545A itself is pulling down on the clock line.

    However, it may be possible that you have communication on one of the down-stream channels which is getting through to the main bus at power up, but we would need to verify that (it should not happen).

    Can you get a better waveform (with more time-scale resolution). Your time-scale is 100us per divison. As reference, you could very well be seeing aliasing from actual i2C communications.