For the AD5428, I want to run this DAC from a 3v3 or 5V rail (Vdd), supply the input lines (8 bit parallel input) with 3v3 ttl signals, and have a reference voltage of 5V. Can I supply the 8 input lines with 3v3 ttl signals if I run the DAC from 3v3 or 5V? Can I have a higher reference voltage than the DAC supply voltage (Vdd). As in - can I have a reference voltage of 5V and a Vdd of 3v3?
You can use both DVdd and AVdd in the region 2.5V - 5.5V maintaining specified performance.
So you can use a DVdd of 3.3V and an AVdd of 5V or you can use a DVdd of 5V and an AVdd of 3.3V.
You can also have a higher reference voltage than the Vdd. A reference of maximum +-12V is allowed on the Vref pins.