Q
I would like to make sure the AD7690 SDO pin stays in high impedance when I do
not need to use it?
A
SDO is high impedance whenever the ADC is not selected, i.e. when SDI is high.
AD7690
Production
The AD7690 is an 18-bit, successive approximation, analog-to-digital converter (ADC) that operates from a single power supply, VDD. It contains a low power...
Datasheet
AD7690 on Analog.com