WM8978CGEFLSLASHV datasheet(88/118 Pages) WOLFSON

88 / 118 page

WM8978

Production Data

PD, Rev 4.5, October 2011

POWER MANAGEMENT

SAVING POWER BY REDUCING OVERSAMPLING RATE

The default mode of operation of the ADC and DAC digital filters is in 64x oversampling mode. Under

the control of ADCOSR and DACOSR the oversampling rate may be doubled. 64x oversampling

results in a slight decrease in noise performance compared to 128x but lowers the power

consumption of the device.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R10

DAC control

DACOSR128

DAC oversample rate select

0 = 64x (lowest power)

1 = 128x (best SNR)

R14

ADC control

ADCOSR128

ADC oversample rate select

0 = 64x (lowest power)

1 = 128x (best SNR)

Table 66 ADC and DAC Oversampling Rate Selection

VMID

The analogue circuitry will not work when VMID is disabled (VMIDSEL[1:0] = 00b). The impedance of

the VMID resistor string, together with the decoupling capacitor on the VMID pin will determine the

startup time of the VMID circuit.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

Power

management 1

1:0

VMIDSEL

Reference string impedance to VMID pin

(recommended startup time):

00=off (open circuit)

01=75kΩ

10=300kΩ

11=5kΩ (for fastest startup)

Table 67 VMID Impedance Control

BIASEN

The analogue amplifiers will not operate unless BIASEN is enabled.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

Power

management 1

BIASEN

Analogue amplifier bias control

0=disabled

1=enabled

Table 68 Analogue Bias Control

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