Hi everyone, does this simple switch for interrupting the HDMI connection in the event of a 3.3V drop make sense?

It's not mine; I found it a while ago on a schematic; I don't remember where it came from .. but I can't tell if it's correct. I'm asking for your opinion.

Is the Drain, Source, and Gate assignment correct?


Is the logic that the MOSFET opens when 3.3 V is missing?
Unfortunately, I don't have any information about the signal on the source.

 

Have you looked at the data sheet for your chosen MOSFET? Rake note of the gate-source voltage.

Ron

 

That works if,and only if, the connected equipment provides an active pull-up and the HDMI_CTRL_DAT signal is always outgoing (ie input into the MOSFET) and is either close to 0v or a positive voltage typically >=3v (as is most likely the case with a logic signal).

When the gate is at 3.3v and the input is <= approx 1.5v, then the MOSFET turns on and the drain is pulled down to the input voltage; generally the input would be logic 0, ie <1v, thus passing through the logic 0 to the connected equipment.

When the gate is at 3.3v and the input is >= approx 2.5v the MOSFET is turned off and the drain is effectively an open circuit, so the connector is either floating (not ideal for a logic signal) or pulled up to logic 1 by the connected equipment.

When the 3.3v gate signal isn't present, the MOSFET is always off so the input is ignored, as long as it's >= 0, and the drain floats to whatever level is defined by the pullup from the connected equipment.