When powering only VDD1(2) a voltage appears on the un-powered VDD.
The leakage current is about 35uA.
The voltages on each of the ADUM1402 pins are as follows -
1, 7 - +5V1 supply
2, 8 - GND1
3 - 10k to GND1
4 - driven High by uC.
5 - uC input pin with pull-up.
6 - Not connected
9, 15 - GND2
10 - +5V2 supply (turned off)
11 - 10k to GND2
12 - connected to unpowered uC.
13 - connected to unpowered uC.
14 - not connected.
16 - +5V2 supply (turned off), when this pin is not lifted, it measures 0.15V. When lifted off PWB, the voltage is 0.65V and it sinks 35uA into 4.72K.