Question:
Will there be signal through the NC contacts when there is no power applied to the ADG722 and ADG884?
Answer:
Although the signals can be seen propagating through without powering up the IC, it is not a reliable way to operate the IC. According to the datasheet, it is not recommended that the customers send the signals through these input contacts without powering up the IC first as it violates the abs max limits given below:
As shown above, analog inputs and digital inputs should not exceed VDD by 0.3V repeatedly as it could result in unexpected behavior in the long term.
Although the customers would see the signal propagating through without powering up the IC due to esd diodes powering up the VDD rail.
If this operation is not ideal for customer's application, ADI recommends customers use ADG7421F in their application. These switches do not have this issue.
The ADG7421F is a low voltage, dual single-pole/single-throw (SPST), low on-resistance switch that features overvoltage protection, power-off protection, and overvoltage detection on the source
pins. Its Pin S1 and Pin S2 are protected against voltages greater than the supply rails, up to ±60 V in both powered and unpowered states.
pins. Its Pin S1 and Pin S2 are protected against voltages greater than the supply rails, up to ±60 V in both powered and unpowered states.