1) The datasheet for the ADXRS646 says essentially nothing about the load characteristics of the Vratio pin. I need to know the requirements for driving this pin: load current sink/source, impedance to ground, etc.
2) Is it possible to drive Vratio with a resistor voltage divider? If so, should it be bypassed, and with what capacitance? Although there might be some error due to loading (see question 1) would that be constant, and so not a noise source?
3) What are the requirements for the voltage on this pin with respect to the other two supply pins aside from when actually using the output signal? If I drive this pin from a voltage that doesn't sequence the same way as the other two supplies, are there potential problems? E.g. if this pin is driven to 3 Volts but the AVcc and Vdd pins are at zero volts, will the device be damaged? Will there be a large current flow? For that matter, what about power sequencing of AVcc and Vdd? Is any special care required if they are driven separately from each other?