WM8741 datasheet(19/63 Pages) WOLFSON

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WM8741

PP Rev 1.3 October 2007

DEVICE DESCRIPTION

INTRODUCTION

The WM8741 is an ultra high performance DAC designed for digital audio applications. Its range of

features makes it ideally suited for use in professional recording environments, CD/DVD players, AV

receivers and other high-end consumer audio equipment.

The WM8741 is a complete differential stereo audio digital-to-analogue converter. The system

includes a dithered digital interpolation filter, fine resolution volume control and digital de-emphasis,

followed by a multi-bit sigma delta modulator and switched capacitor multi-bit stage with differential

voltage outputs. The device supports both PCM and DSD digital audio input formats.

The WM8741 includes a configurable digital audio interface support for a 3-wire and 2-wire serial

control interface, and a hardware control interface.

The software control interface may be

asynchronous to the audio data interface; in which case control data will be re-synchronised to the

audio processing internally. It is fully compatible with, and an ideal partner for, a range of industry

standard microprocessors, controllers and DSPs.

Uniquely, the WM8741 has a large range of high performance low latency advanced digital filters.

The full range of filters is selectable in software mode, and a limited range of filters are available

under hardware control. The filters allow users the flexibility to choose characteristics to match their

group delay, phase and latency requirements.

Operation using a master clock of 128fs, 192fs, 256fs, 384fs, 512fs or 768fs is supported. Sample

rates (fs) from 32kHz to 192kHz are allowed, provided the appropriate master clock is input (see

Table 1 for details).

In normal PCM mode, the audio data interface supports right justified, left justified and I

2S interface

formats along with a highly flexible DSP serial port interface.

There are two DSD modes. In DSD Direct mode, the datastream is subjected to the minimum

possible processing steps between input and output.

In DSD Plus mode, the datastream is

converted to PCM and filtered to allow reduction of out of band components. This step also provides

additional benefits in allowing access to other PCM features such as volume control and advanced

digital filtering.

The device is packaged in a small 28-lead SSOP.

CLOCKING SCHEMES

In a typical digital audio system there is only one central clock source producing a reference clock to

which all audio data processing is synchronised. This clock is often referred to as the audio system’s

Master Clock. The external master system clock can be applied directly through the MCLK input pin

with no software configuration necessary for sample rate selection.

MCLK is used to derive clocks for the DAC path in PCM mode. The DAC path consists of DAC

sampling clock, DAC digital filter clock and DAC digital audio interface timing. In a system where

there are a number of possible sources for the reference clock it is recommended that the clock

source with the lowest jitter be used to optimise the performance of the DAC.

CONTROL INTERFACE

The WM8741 supports 2-wire and 3-wire serial control, and hardware control. Selection of control

mode is made by controlling the state of the MODE pin.

NAME

DESCRIPTION

MODE/

LRSEL

0 = Hardware control mode

1 = 3-wire serial control mode

Z = 2-wire serial control mode

Table 8 Control Mode Configuration

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