I'm self-taught in electronics and while I can do the digital stuff fairly readily, analog throws me for a loop. I'm looking at an audio CODEC and the reference schematic has this on the input to the ADC:
I understand that C11 is there to capacitively couple the input to the ADC and to prevent any DC offset from the input to feed into the op-amp front end of the ADC.
What purpose(s) do C12, R1, and R2 serve?
(In case anyone is wondering, this is the reference schematic from the Wolfson WM8731 CODEC. http://www.wolfsonmicro.com/products/audio_hubs/WM8731/)