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

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

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.

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

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

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.

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

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.