WM8352 datasheet(101/336 Pages) WOLFSON

101 / 336 page

Production Data

WM8352

PD, February 2011, Rev 4.4

101

13.12.3 MID-RAIL REFERENCE (VMID)

VMID provides a potential mid-way between AVDD and GND, used in many parts of the audio

CODEC. It is generated from AVDD using on-chip potential dividers. Different resistor values can be

selected for this purpose. A medium resistance should be used when the CODEC is active. A high

resistance option provides a more power-efficient way to maintain the VMID voltage when the

CODEC is in “Standby” (i.e. inactive but ready to start immediately, without needing to wait for the

VMID capacitor to be charged). For startup and shutdown the VMID generator provides soft VMID

ramping to reduce pops and clicks. The speed of this ramp is selectable using the anti-pop controls

and can be tuned to the application.

Figure 62 Generating the Mid-rail Reference

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R8 (08h)

Power

Management 1

VMID_EN

Enables VMID resistor string

0 = disabled

1 = enabled

1:0

VMID [1:0]

(off)

Resistor selection for VMID potential divider

00 = off

01 = Vmid comes from 300kΩ R-string

10 = Vmid comes from 50kΩ R-string

11 = Vmid comes from 5kΩ R-string

Table 50 Controlling the Mid-rail Reference

WM8352 Datasheet(PDF) 101 Page - Wolfson Microelectronics plc