I have some problems for designing a circuit based on AD9218. This is my first time to learn this IC, and make PCB layout by myself.
The datasheet of AD9218 shows that pins 13,30,31,48 are the same pin for Analog Supply (Vd), but they aren't short between (13,48) and (30,31). Would you tell me how do I supply the voltage? When I supply 3V for pin (13,48), the other pin's (30,31) voltage is 2V which is lower than minimun Vd (2.7V) in datasheet.
Secondly,the datasheet provide a driver schematic for inputs https://dl.dropbox.com/u/32176429/8138driver.jpg but I don't have this IC. Can I use the AD8056 to driving AD9218? https://dl.dropbox.com/u/32176429/8056driver.jpg
There is a difference between this two pictures, AD8138 has a capacitor between differential inputs and AD8055 doesn't. Is the capacitor required? Should I use the same capacitor (15pF) between the differential inputs?
Thanks for your help.