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ADG507A multiplexer ground

Question asked by Bendr on Feb 27, 2018

Hi,

 

I'm working with the ADG507A Multiplexer. I currently have it set according to the schematic:Schematic showing ADG507A Ground Configuration with Power supply common and Digital ground connected

The output goes to an AD595 Thermocouple Amplifier, and the input connects to a grounded thermocouple. The AD595 requires a connection to ground from the thermocouple, which forces the 1Mohm resistor from the thermocouple to the power supply common.

 

We have had some concern that the digital ground could inject noise through the analog input to anything on the other end. So we are considering isolating the power supply common and the inputs from the digital ground and the IC ground, like the following schematic:

 

 

Schematic showing ADG507A Ground Configuration with Power supply common and Digital ground isolated.

Can the ADG507A operate in this configuration? Or does it require a reference to the power supply common?

 

Thanks,

Benjamin Russon

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