WM8993 datasheet(125/229 Pages) WOLFSON

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Production Data

WM8993

PD, November 2010, Rev 4.0

125

AUTOMATIC CLOCKING CONFIGURATION

The WM8993 supports a wide range of standard audio sample rates from 8kHz to 48kHz. The

Automatic Clocking Configuration mode simplifies the configuration of the clock dividers in the

WM8993 by deriving most of the necessary parameters from a minimum number of user registers.

Automatic Clocking Configuration mode is selected by the SR_MODE bit. When Automatic mode is

selected (SR_MODE = 0), some of the Manual clocking configuration registers are invalid and

ignored. The affected registers are indicated in Table 82 and Table 83.

In Automatic mode, the SAMPLE_RATE field selects the sample rate, fs, of the ADC and DAC. Note

that, in Automatic mode, the same sample rate always applies to the ADC and DAC.

In Automatic mode, the CLK_SYS_RATE field must be set according to the ratio of CLK_SYS to fs.

In Automatic mode, 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.

In both Manual and Automatic modes, the CLK_SYS_RATE register must be set; this determines the

operating behaviour of the headphone amplifier Charge Pump circuit.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R10 (0Ah)

DAC CTRL

DAC_OSR128

DAC Oversample Rate Select

0 = disabled

1 = enabled

For 48kHz sample rate, the DAC

oversample rate is 128fs when

DAC_OSR128 is selected.

This is valid in Automatic mode only.

The default is 64fs.

R65 (41h)

Clocking 3

9:7

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

4:1

CLK_SYS_RAT

E [3:0]

0011

Selects the CLK_SYS / fs ratio

0000 = 64

0001 = 128

0010 = 192

0011 = 256

0100 = 384

0101 = 512

0110 = 768

0111 = 1024

1000 = 1408

1001 = 1536

R66 (42h)

Clocking 4

SR_MODE

Selects Clocking Configuration mode

0 = Automatic

1 = Manual

Table 81 Automatic Clocking Configuration Control

WM8993 Datasheet(PDF) 125 Page - Wolfson Microelectronics plc

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