WM8985GEFLSLASHR datasheet(91/121 Pages) WOLFSON

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Production Data

WM8985

PD, Rev 4.6, July 2009

VMID

The analogue circuitry will not operate unless VMID is enabled. The impedance of the VMID resistor

string, together with the decoupling capacitor on the VMID pin will determine the start-up time of the

VMID circuit.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1 (01h)

Power

management 1

1:0

VMIDSEL

Reference string impedance to VMID pin

00 = off (250kΩ VMID to AGND1)

01=75kΩ

10=300kΩ

11=5kΩ

Table 51 VMID Impedance Control

BIASEN

The analogue amplifiers will not operate unless BIASEN is enabled.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R1 (01h)

Power

management 1

BIASEN

Analogue amplifier bias control

0 = disabled

1 = enabled

Table 52 Analogue Bias Control

POP MINIMISATION

POBCTRL

WM8985 has two bias generators. A noisy bias derived from AVDD and a low noise bias derived

from VMID. POBCTRL is use to switch between the two bias generators. During power up, the

AVDD derived bias is available as soon as AVDD is applied; the VMID derived bias is available once

the VMID node has charged up.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R42

OUT4 to ADC

POB

CTRL

VMID independent current bias control

0 = Disable VMID independent current

bias

1 = Enable VMID independent current bias

Note:

POBCTRL should be asserted during power up to minimize pops and then de-

asserted at the end of the power up sequence to give best performance. Refer to

Recommended Power Up/Down

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