Question
I checked the datasheet, this part can work with the same power supply on Vcca
and Vccy, but some cautions should be noted:
1. the power supply issue on page 16 of its datasheet.
2. For not high speed applications (this part is designed for 25Mbps min),
you'd better add some series resistors to slow down the rise/fall edges of the
logic signals to eliminate ripples on the logic waveforms.
Answer
For normal operation VCCA must be less than or equal to VCCY as stated in the
datasheet. If this condition is not met, say VCCY>VCCA, the supply current
drawn by the VCCA pin may increase significantly and damage the ADG3304. To
avoid this situation when the IC card is not present, I would recommend to use
a diode between VCCA and VCCY (anode to VCCA and cathode to VCCY). This ensures
that VCCY does not go below VCCA when the card is removed. Also, the customer
may consider to implement a circuitry that grounds the EN pin when the card is
not present. This will disable the ADG3304 and reduce the power consumption to
a minimum.