The ADuM144x family contains Schmitt trigger input buffers, which provide hysteresis for noise rejection. During an input transition a Schmitt trigger will introduce a small shoot-through current while the input is near the mid-supply level. In devices with higher average power dissipation this not noticeable, but in ultra-low power parts like the ADuM144x it can be large compared to the average supply current. It is recommended that the inputs be driven with 0.5 V of VDD and GND to achieve the lowest power dissipation.
For more information on the ADuM144x family of low power digital isolators, please visit: www.analog.com/ADuM144x