AC COUPLING RESISTORS ON DDR TERMINATION RAIL

[pacman22]

Hey!

This is a schematic of DDR3. I observed that the termination voltage rail VTT (0.65V) is coupled to VDD_DDR (1.35V).
What purpose does it serve, is it really required? Also, there are multiple capacitors, can they be replace by one equivalent capacitor?

 

[FvM]

A better title would be "VTT bypass capacitors" rather than "AC coupling resistors".

It's generally reguired to have multiple bypass capacitors for VTT net as well for supply voltages to create low impedance rails. Usually all bypass capacitors are referenced to GND, don't know why they used VDD instead. Possibly VDD near VTT copper pour.