WM8985GEFLSLASHR datasheet(87/118 Pages) WOLFSON

87 / 118 page

Pre-Production

WM8985

PP, Rev 3.4, October 2006

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 ADCOSR128 and DACOSR128 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 (0Ah)

DAC control

DACOSR128

DAC oversample rate select

0 = 64x (lowest power)

1 = 128x (best SNR)

R14 (0Eh)

ADC control

ADCOSR128

ADC oversample rate select

0 = 64x (lowest power)

1 = 128x (best SNR)

Table 48 ADC and DAC Oversampling Rate Selection

LOW POWER MODE

If only DAC or ADC functionality is required, the WM8985 can be put into a low power mode. In this

mode, the DSP core runs at half of the normal rate, reducing digital power consumption of the core

by half. For DAC low power only, 3D enhancement with 2-Band equaliser functionality is permitted,

where only Band 1 (low shelf) and Band 5 (high shelf) can be used. For ADC low power, the

equaliser and 3D cannot be used.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R7 (07h)

Additional Ctrl

M128ENB

0 = low power mode enabled

1 = low power mode disabled

Table 49 DSP Core Low Power Mode Control

There are 3 modes of low power operation, as detailed below. The device will not enter low power

unless in one of these register configurations, regardless of M128ENB.

For pop-free operation of the device it is recommended to change the M128ENB low power

functionality only when both the DACs and ADCs are disabled, i.e. when DACENL=0, DACENR=0,

ADCENL=0 and ADCENR=0.

FUNCTION

SETTING

DESCRIPTION

ADC low power

M128ENB

ADCENL

ADCENR

DACENL

DACENR

EQ3DMODE

1 (DAC path)

Either or both of ADCENL and

ADCENR must be set (mono or

stereo mode)

DAC low power

M128ENB

ADCENL

ADCENR

DACENL

DACENR

Either or both of DACENL and

DACENR must be set (mono or

stereo mode)

EQ3DMODE = 0: EQ in ADC path

EQ3DMODE = 1: EQ in DAC path

Table 50 DSP Core Low Power Modes for ADC Only and DAC Only Modes

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