I am looking at the recommended circuit for the ADV7180 by Analog Devices and trying to understand some of the reasoning behind the design choices. I realize some of these questions may be a lack of understanding of some fundamental concepts and would really appreciate if someone could explain them to me.
I know that the XTAL inputs are used for the 28.63636Mhz crystal but I don't understand how they came up with the circuit shown. What is the purpose of the additional resistors and the capacitors in this case?
For the ELPF input, from reading the datasheet all I could get was that it is the "External Loop Filter" pin and must be placed as close as possible to the IC. What is the purpose of this pin and again, how does the recommended design work?
The data sheet can be found here: http://www.analog.com/media/en/technical-documentation/data-sheets/ADV7180.pdf