I am using some ADG1608 to multiplex 0~+5V analog signals. They are connected in a way that 2 signals are fed to 2 ADG1608, just 1 of the ADG1608 is powered with VCC=5V, VSS=0V and another one has no VCC connected.
There is no problem in switching the signal from 0V to around 3.6V. But when the input signal goes higher than 3.6V, we saw up to 100mA current follow to signal path. When we connect the second ADG1608's VCC to +5V, the problem is cleared.
Is there any path from S or D in ADG1608 to VCC pin that made this happen? We guess there is a path to VCC pin when we have no power.