I am curious what the expected behavior is when exceeding the maximum input voltage for the AD7173 analog inputs with the input buffers enabled.
I have an AD7173 configured with the input buffers enabled. The signal I am measuring has a max differential voltage of 3.75V and the negative side of the differential input is connected to a 1.25V reference. I am powering AVDD1 and AVDD2 with 5V and IOVDD with 3.3V. This means I may exceed the max input voltage of AVDD1 - 1.1 = 3.9V. I would imagine I would be railing the input amplifier output at 3.9V when I exceed this limit. I would expect this would result in a max sense voltage of approximately 2.65V (one input amp railed at 3.9V, other operating nominal at 1.25V). What I'm seeing is that the max sampled voltage is in the range of 3.06 to 3.17V. Is this behavior expected? If so, can someone explain what's going on?
Thanks so much for your help.