Seeking STM processor that has wide mux feed the pga-OpAmp then feed ADC

[MJohn.11]

Have found great info on very flexible op amp with pga ability. The STM32H7 - OpAmp presentaion for example.

Have found great info on ADC subsystem in the STM32H7 - ADC presentaion and in datasheets for specific STM32H7 part(s).

Have seen the very wide direct from IO pins 8 or more input mux to feed the ADC.

Of course I am likely asking too much BUT is there an STM part that has for example 2 8 or more input muxs from IO pins feed one of two PGA opamps and THEN have that op amp feed one of two ADC units in 12 bit mode?

Yes, this is asking a lot but I have been unable to find it so far.

I have seen the G series parts with much smaller 3 or 4 way mux in front of op amp but don't know if that part could then feed a couple ADC or not.

Thank you in advance for any tips, it is just very hard to find which makes me feel it is just too advanced to exist (yet).

[MJohn.11]

Another solution would be some very wide muxs of 8 or more inputs from pins come back OUT of the part. In that case they could go back into the PGA followed by the ADC. Thank you.

[waclawek.jan]

The STM32 are primarily digital circuits with limited analog functionality. Consider using external analog mux, such as the venerable CD450x http://www.ti.com/lit/ds/symlink/cd4051b.pdf?ts=1588143044134

You can also consider (ab)using the touchscreen functions in some STM32, but still it's better to use external analog mux.

JW

[DCraw.1]

Well it really seems like this is an obvious thing that people would want right? But sadly I've not been able to figure out how to do it with the ST parts.

Extremely frustrating that you, apparently, can't make this work.

[waclawek.jan]

> Extremely frustrating that you, apparently, can't make this work.

What exactly do you mean by "this"?

JW

[DCraw.1]

Let ,me be more precise.

It is extremely frustrating that it seems impossible to connect the wide muxes that obviously exist on the STM32H7 parts to the PGA to the ADC. As hooking things up in that precise order is something that people obviously would want to do.

[waclawek.jan]

Yes maybe, but then I see also a lot of missed opportunities in the digital domain with STM32s.

Chalk it up to the 2020 wishlist. Wait, there's no 2020 wishlist, as we still wait for some salesforce feature to be enabled.

JW

[MJohn.11]

I asked a co-worker to contact an ST apps person and that happened a couple days ago. The answer was that the mux cannot feed the VGA as is known and explained by others above. My definitive answer has been accepted. That being said we are moving on with external mux. As far as 'Wish List' I would say that you never know how the user wants to feed the VGA but the simplest way is have just a VGA ability and the mux outputs go to respective VGA where the VGA is a non-inverting VGA that will accept DC biased signals then go into the ADC. We will be riding a signal around a bias of around 1.5V for example. In our case an inverting VGA would be ok too. A more complex method would allow mux to come back out but to me that seems a bit not in character with a SoC where you want to integrate a mux and not just be supplying a mux in your high power silicon as an isolated component. Having a VGA between mux out and ADC inputs is a good SoC feature.

Thank you for all your inputs and posts. It has been very helpful to resolve this issue and perhaps add to perhaps an already large wish list. Still, that is why it is a wish list LOL.

Stay Healthy, Mark