I'm finding a dearth of data about the Aux ADC input in either it's datasheet or user's guide.. I'm guessing (and I hate that) it's a high impedance CMOS input with low capcitance ESD diodes to the rails, but I can't find any information in the documentation that specifies any other than operating input voltage range. I don't even see applicable ABSOLUTE MAXIMUM RATINGS for the non-RF analog inputs.
I'm going to feed the AuxADC input through an op-amp buffer operating off a 3.3 V supply. While my input is nominally 1 VDC or less, I want to insure that transient conditions do not damage the AD9364 input. I plan to feed the AuxADC input through a series resistor with a shunt 680 pF cap to ground as recommended in the UG. Given the lack of specifications I've found, I don't have a good idea how to size this resistor. My initial WAG is NMT (3.3V-1.3V)/2mA ~1K which still lets the input settle is a reasonable time for my application.
Does anyone know where I can find typical input specs for this port? Things like max ratings, offset and impedance specs, etc? I'm looking for design guidance, not guaranteed tested values.