WM8753L datasheet(69/92 Pages) WOLFSON

69 / 92 page

WM8753L

Pre-Production

PP Rev 3.4 November 2005

AUDIO SAMPLE RATES

The WM8753L has two modes of operation for the HiFi DAC, ADC and voice DAC sample rates,

selectable using control bit SRMODE:

HiFi ADC and DAC at different sample rates Mode (IFMODE [1:0] = 11) SRMODE=0. HiFi DAC and

stereo ADC used for high quality playback and record. The Voice DAC is unused. Sample rate control

is via control bits SR[4:0] and USB.

Voice CODEC + HiFi DAC Mode (IFMODE [1:0] =00) SRMODE = 1. HiFi DAC is used for high quality

playback; Stereo (or mono) ADC and voice DAC are used for voice record and playback. HiFi DAC

Sample rate is controlled by SR[4:0] and USB. Voice CODEC sample rate is controlled by PSR.

In either mode of operation the ADCs and DACs may be powered off if not required to allow e.g. HiFi

DAC playback only, with ADCs disabled. The HiFi DAC sample rate is always controlled by SR[4:0]

and USB.

HIFI CODEC MODE

In this mode the Voice DAC is unused and the stereo ADC is used for HiFi record.The WM8753L may

be configured to run from a clock generated by the on-chip PLL or may be driven from an external

clock connected to the MCLK pin. The WM8753L supports a wide range of master clock frequencies

on the MCLK pin, and can generate many commonly used audio sample rates directly from the

master clock. In HiFi CODEC Mode the ADC and DAC do not need to run at the same sample rate;

several different combinations are possible.

There are two clocking modes:

•

‘Normal’ mode supports master clocks of 128fs, 192fs, 256fs, 384fs, and their

multiples (Note: fs refers to the ADC or DAC sample rate, whichever is faster)

•

USB mode supports 12MHz or 24MHz master clocks. This mode is intended for use

in systems with a USB interface, and eliminates the need for the internal PLL to

generate the clock frequency for the audio CODEC.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

SRMODE

ADC Sample rate mode

0 – ADC sample rate selected

by SR[4:0] and USB

1 – ADC sample rate selected

by PSR

[5:1]

SR [4:0]

00000

Sample Rate Control

R6 (06h)

Sample Rate

Control (1)

USB

Clocking Mode Select

1 = USB Mode

0 = ‘Normal’ Mode

Table 66 Clocking and Sample Rate Control

The clocking of the WM8753L Hi-Fi CODEC is controlled using the MCLK1DIV2, USB, and SR

control bits. SR allows the user to change the ADC and DAC sample rates without changing the

master clock frequency. Setting the MCLK1DIV2 bit divides MCLK by two internally. The USB bit

selects between ‘Normal’ and USB mode. Each value of SR[4:0] selects one combination of MCLK

division ratios and hence one combination of sample rates (see next page). Since all sample rates

are generated by dividing MCLK, their accuracy depends on the accuracy of MCLK. If MCLK

changes, the sample rates change proportionately.

Note that some sample rates (e.g. 44.1kHz in USB mode) are approximated, i.e. they differ from their

target value by a very small amount. This is not audible, as the maximum deviation is only 0.27%

(8.0214kHz instead of 8kHz in USB mode). By comparison, a half-tone step corresponds to a 5.9%

change in pitch.

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