WM8904ECSSLASHR datasheet(105/188 Pages) WOLFSON

105 / 188 page

Pre-Production

WM8904

PP, Rev 3.3, September 2012

105

A high performance mode of DAC operation can be selected by setting the DAC_OSR128 bit; in

48kHz sample mode, the DAC_OSR128 feature results in 128x oversampling. Audio performance is

improved, but power consumption is also increased.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R33 (21h)

DAC Digital

DAC_OSR128

DAC Oversample Rate Select

0 = Low power (normal OSR)

1 = High performance (double OSR)

R21 (15h)

Clock Rates

13:10

CLK_SYS_RAT

E [3:0]

0011

Selects the SYSCLK / fs ratio

0000 = 64

0001 = 128

0010 = 192

0011 = 256

0100 = 384

0101 = 512

0110 = 768

0111 = 1024

1000 = 1408

1001 = 1536

2:0

SAMPLE_RATE

[2:0]

101

Selects the Sample Rate (fs)

000 = 8kHz

001 = 11.025kHz, 12kHz

010 = 16kHz

011 = 22.05kHz, 24kHz

100 = 32kHz

101 = 44.1kHz, 48kHz

110 to 111 = Reserved

Table 62 Automatic Clocking Configuration Control

ADC / DAC CLOCK CONTROL

The clocking of the ADC and DAC circuits is derived from CLK_DSP, which is enabled by

CLK_DSP_ENA. CLK_DSP is generated from SYSCLK which is separately enabled, using the

Two modes of ADC operation can be selected using the ADC_OSR128 bit; in 48kHz sample mode,

setting the ADC_OSR128 bit results in 128x oversampling. This bit is enabled by default, giving best

audio performance. Deselecting this bit gives 64x oversampling in 48kHz mode, resulting in

decreased power consumption.

Higher performance DAC operation can be achieved by increasing the DAC oversample rate - see

Table 62.

The ADC / DAC Clock Control registers are defined in Table 63.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R10 (0Ah)

Analog ADC 0

ADC_OSR128

ADC Oversampling Ratio

0 = Low Power (64 x fs)

1 = High Performance (128 x fs)

R22 (16h)

Clock Rates 2

CLK_DSP_ENA

DSP Clock enable

0 = Disabled

1 = Enabled

Table 63 ADC / DAC Clock Control

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