We will replace ADuM131 with ADuM142 on same pcb board.
So, one input pin and one output pin would be unconnected state.
Is it okay?
The unused channel D input should be tied high or low to prevent the output from toggling in a noisy environment. I would recommend setting the channel input to the lower power consumption state where the transmitter is off. Tie the input high for the ADuM142E1 and low for the ADuM142E0 to do so. The channel D output would be left floating.