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TMUX1208: Signal connect to TUMX1208 voltage can't 0V

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Replies: 9

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Part Number: TMUX1208

Hi team,

Now I have a question about TMUX1208. I confirm that the signal of our master voltage is from 1.8V to 0V. When I connect to TUMX1208 "S" input, I find the signal's voltage can't low to 0V. It's voltage may be 0.6V.

I don't know why it happened.

Is there any wrong with the application? Thanks a lot!

  • The most likely reason is that there is a pull-up resistor somewhere on the line. (The schematic is incomplete.)

  • In reply to Clemens Ladisch:

    Hi Clemens Ladisch,

    I just only connect TMUX1208 now but it seems the same problem.(Delete R487)

    When I cut R170 and I measure R170.1 the signal is good. But when I recovery R170  this issue has happened.

    I check there is no pull-up resistor in my line.

  • In reply to Max CHANNG:

    Is there a pull-up resistor configured on pin T10?

  • In reply to Clemens Ladisch:

    Hi Clemens Ladisch,

    T10 is our SOC pin. I confirm there is a pull-down in SOC internal.

  • Max,

    Is master voltage feeding into S1 in these? Have you tried probing S1 without the master connected? Is the problem only occurring when the signal is sent or is there always 0.6V on that line?
    Do you also see this voltage on all lines or is there only 0.6V present where there should be 0V on the master clock line that you're using. 

    If I understood your exchange with Clemens, the problem was resolve when you removed the R170 the problem is resolved. Is there a reason for wanting to keep the resistor? What current is being driven here?

    Rami

  • In reply to Rami Mooti1:

    R170 looks like a 0 Ω link and connects the switch to the SoC, so it's kind of important.

    The problem appears to be caused by the SoC. Apparently, the pull-down is actually a pull-up.

  • In reply to Clemens Ladisch:

    Clemens

    it seems I was a bit presumptuous and thought by removing the resistor, he also shorted it and the problem was resolved.

    Max,

    My feelings are the same as clemens here. It does appear that there's a pull-up rather than a pulldown internally here so you arent grounding the signal on low. Have you double checked the soc intenal architecture?

    Rami

  • In reply to Rami Mooti1:

    Hi Clemens, hi Rami,

    Thanks for your Reply.

    I will double-check the SOC internal architecture. If I have something results I will tell you.

  • In reply to Max CHANNG:

    Hi Clemens, hi Rami,

    I measure our system board 5pcs. I just find only 1 pcs has this issue.

    When I let SW update the SOC code. I find this issue has not happened.

    Thank you for the directions.

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