Hello! I have been reading this post for a big question that I had and I think I even screw it up in my design.
So I have a MUX506, controlled by an ESP32, and right now is not working, what I did was to connect only one power supply of 12V to VDD, and then all the control (A0...A3) is connected directly to the ESP32 (3.3V) and the D signal is connected directly to the analog input of the ESP32.
I am confused because on the first section of the datasheet of the mux said that the logic levels could be from 2V to VDD.
The signals that I am trying to read are on the range of 0 to 3.3V
Any idea of what I am doing wrong?

Mod:link to Old Thread.
https://forum.allaboutcircuits.com/threads/mux506-fail.171523/post-1534987

 

The MUX506 has three(3) power related pins, which are Vdd, Vss, and GND. You said in post #1 that the logic levels can be between +2V and VDD. This is not quite correct. You did not say which pin the voltage levels are with respect to. An actual schematic of your setup would be a big help. As I read the datasheet, I believe that Vss and GND can be connected together, but that is not necessarily a requirement.
The actual thresholds are:

1. Logic High is > 2V
2. Logic Los is <0.8V

Those are standard TTL levels, and they should be measured with respect to GND, not Vss

 

i see the ´506 first-time and it's hard to figure out is the figure "simpliifed schematic" presenting the entire chip or is the 2-nd leftmost "rectangle" on the Fig.42 it or is the Fig.32 "2 B" trusted about the active channel electrical setup ???

other than that since the single supply powering is not hinted . . . /!\ i assume you connect the 12V to Vdd and SGND/COMMON to Vss ? leaving the GND "floating" /!\

= Call "Mom" https://www.ti.com/info/contact-us.html

Edit -- it seems the d/s does hint (though poorly) the single-supply powering at the end of the pg.5 :
VSS 27 Power supply "Negative power supply. This pin is the most negative power supply potential. In single-supply applications, this pin ?? can be ?? connected to ground. For reliable operation, connect a decoupling capacitor ranging from 0.1 μF to 10 μF between VSS and GND."
??? aswell it can be and not ??? - (GD alchemists)

 

So from what I understeand if you need only one power supply you just connect the power supply to VDD and then VSS to ground so thats what I did, I am attaching an schematic of what I did. The ESP32 at the output is sending just 3.3V that goes directly to A0...A3


Mod: added d/s for 506

 

All of the analog input pins, S1,...,S16 appear to be floating. Is this intentional?

 

Yep I did connect them I am connecting a few sensors overthere, I just did that to generate an general idea of the schematic.

 

the google can find : Crosstalk , BW versus supply , Settling ~ channel ON resistance against supply
? are you sure your soldering , copper traces and connectors are . . . conducting . . . the MUX didn't get damaged by overvoltage/ESD ? . . .
? the MCU side input port is configured correct (don't know this particular MCU - but there might be need to set some flags-/mask- -reg.-s extra to port I/O assignment) = did you tested the port for input (so to say) "standalone" (without the MUX connected)
something (i doubt incomplete at) https://randomnerdtutorials.com/esp32-adc-analog-read-arduino-ide/
+ a random jump to ports cfg. https://www.espressif.com/sites/def...2_technical_reference_manual_en.pdf#iomuxgpio (← i won't work through this)
? , + https://www.espressif.com/sites/def...nical_reference_manual_en.pdf#subsection.29.3
https://www.espressif.com/sites/def...reference_manual_en.pdf#subsubsection.30.4.11

 

Looks like you were right, I was doing something wrong with my controller it turns out, that some of my "outputs" can only works as an inputs, so there was my mistake, the good thing is that the MUX can work perfect using 12V on VCC, VSS to ground and then the A0...A3 works fine with 3.3V

the google can find : Crosstalk , BW versus supply , Settling ~ channel ON resistance against supply
? are you sure your soldering , copper traces and connectors are . . . conducting . . . the MUX didn't get damaged by overvoltage/ESD ? . . .
? the MCU side input port is configured correct (don't know this particular MCU - but there might be need to set some flags-/mask- -reg.-s extra to port I/O assignment) = did you tested the port for input (so to say) "standalone" (without the MUX connected)
something (i doubt incomplete at) https://randomnerdtutorials.com/esp32-adc-analog-read-arduino-ide/
+ a random jump to ports cfg. https://www.espressif.com/sites/def...2_technical_reference_manual_en.pdf#iomuxgpio (← i won't work through this)
? , + https://www.espressif.com/sites/def...nical_reference_manual_en.pdf#subsection.29.3
https://www.espressif.com/sites/def...reference_manual_en.pdf#subsubsection.30.4.11

 

Looks like you were right, I was doing something wrong with my controller it turns out, that some of my "outputs" can only works as an inputs, so there was my mistake, the good thing is that the MUX can work perfect using 12V on VCC, VSS to ground and then the A0...A3 works fine with 3.3V

Glad you were able to quickly get to the root of the problem. Good luck with your project.