AD7938 FPGA Input Channel Voltage

Hello All,

I am facing an interesting issue.  I have designed an RTL module with the AD938 A to D.  I am referencing an external source 4.096V I am able to read channels so I think my logic is correct. So, let's say I have channel 1 at 4 v  my reading for the channel is 4095 which is correct.  Channel 2 starts at 0 V which reads 0, so far this is correct. Now, when I try to ramp up channel 2 voltage I see the channel 1 reading drop without adjusting its voltage input.  I can see the input voltage in channel 1 not change but my reading value dropped.  Any ideas?