What is the function of the VMID pin in NUC505? How to design the circuit diagram?

[a_ziliu]

VMID is the microphone reference voltage, which must be connected to the MICN when the microphone is configured for single-ended input.
As shown, the suggested components are C1=220pF, C2=1uF, R1=680ohm~2.2kohm, R2=0ohm.

If it is differential input, the connection is the same as the connection on the NUC505 Tiny Board, as shown below.