I use one AD7606-4 on my board. All four channels are configured as below:
But for now, I only need use CH1 and CH2. So I tried several methods:
- Short the input of CH3 and CH4 as below: But after that, my chip don't work well. The data sampled from all 4 channels are messed (my input are 50Hz AC signal).
- Leave the CH3 and CH4's Vx floating, And give CH1 and HC2 same signal (about 1V). The data sampled from CH1 and CH2 is good.
- Leave CH3 and CH4 floating, give CH1 a 20mV AC signal, but CH2 a even smaller one, nearly 0, the data sampled from CH1 occasionally appear a small ‘plateau’ at 0 crossing (crossing-over distortion).
I'm a little confused now. What I should do with the unused inputs?
