How to connect vref to an analog multiplexer

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JS_4155161
Level 1
Level 1

I'm trying to route a reference voltage to an analog multiplexer as shown below but PSOC creator is throwing errors.

Is this at all possible? If so, how?

pastedImage_0.png

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Len_CONSULTRON
Level 9
Level 9
Beta tester 500 solutions authored 1000 replies posted

Surfer,

I've looked at the Cypress info available.  In general, the SIO pins (Port 12) are very versatile but have the limitation that they don't support analog input and indirectly support analog output.

I've included a snippet of a circuit that might be what you intended.  It requires one more pin to achieve.

pastedImage_0.png

In this configuration, vo_ref puts out a vref-limited digital output (<1.024V) with about 1mA drive outside the PSoC.  vo_meas measures the resultant voltage (1.024V -0.5V [depending on the load on vo_ref]).

Hopefully this will address your design issue.

Len

Len
"Engineering is an Art. The Art of Compromise."

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RyanZhao
Moderator
Moderator
Moderator
250 sign-ins First question asked 750 replies posted

Described in datasheet: "Currently, only the GPIOs can be multiplexed with this multiplexer."

The software analog mux can be used for routing the vref signals.

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Len_CONSULTRON
Level 9
Level 9
Beta tester 500 solutions authored 1000 replies posted

Surfer,

Can you supply some info about your use of the pin 12.2 called vo_meas?

It appears you are trying to use this pin in SIO mode.  According to https://www.cypress.com/documentation/application-notes/an60580-sio-tips-and-tricks-psoc-3-psoc-5lp

analog functions are not supported if you are using the vref input.  This input is intended for thresholding for digital inputs or outputs.

Len

Len
"Engineering is an Art. The Art of Compromise."
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Len_CONSULTRON
Level 9
Level 9
Beta tester 500 solutions authored 1000 replies posted

Surfer,

I've looked at the Cypress info available.  In general, the SIO pins (Port 12) are very versatile but have the limitation that they don't support analog input and indirectly support analog output.

I've included a snippet of a circuit that might be what you intended.  It requires one more pin to achieve.

pastedImage_0.png

In this configuration, vo_ref puts out a vref-limited digital output (<1.024V) with about 1mA drive outside the PSoC.  vo_meas measures the resultant voltage (1.024V -0.5V [depending on the load on vo_ref]).

Hopefully this will address your design issue.

Len

Len
"Engineering is an Art. The Art of Compromise."
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