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I am evaluating a 16bit ADC (MCP33131D-05-E/MS) for my project. I want to sample in fully differential mode, but I have doubts as to what voltages are allowed on the Ain+ and Ain-.

Signal conditioning prior to the ADC is done with a dual supply so the voltage swing of the sampled signal will be -5V to +5V.

The datasheet states (on page 1 -> Features) that the ADC has a differential input -VREF to +VREF. This would make it -5V to +5V in my design since I will use a 5V voltage reference.

But then in the absolute maximum ratings it states the following:

Analog inputs w.r.t GND .............. .......... –0.3V to VREF+0.3V

I The question is: can I apply a negative (-VREF) signal to the Ain- or will the magic smoke escape?

Link to the datasheet of MCP33131D-05-E/MS

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The question is: can I apply a negative (-VREF) signal to the Ain-

No. The Ain signals are DIFFERENTIAL, which means that Ain+ can be 0, and Ain- can be VREF, which is -VREF in internal ADC representation. If Ain+=VREF and Ain-=0, it is +VREF. But both inputs must be positive in relation to ground.

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  • \$\begingroup\$ Thank you for the explanation. I will have to level shift the signal before the ADC so that it will be positive relative to ground. \$\endgroup\$ – BPajk Apr 26 at 20:51

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