wm8742 Wolfson Microelectronics plc, wm8742 Datasheet - Page 18

• Manufacturer Part Number: wm8742
• Description: 24-bit 192khz Dac With Advanced Digital Filtering
• Manufacturer: Wolfson Microelectronics plc

WM8742
DEVICE DESCRIPTION
INTRODUCTION
CLOCKING SCHEMES
CONTROL INTERFACE
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The WM8742 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 WM8742 is a complete differential stereo audio digital-to-analogue converter.
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 WM8742 includes a configurable digital audio interface support for a 3-wire and 2-wire serial
control interface, and a hardware control interface.
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 WM8742 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 11 for details).
In normal PCM mode, the audio data interface supports right justified, left justified and I
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.
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.
The WM8742 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.
Table 8 Control Mode Configuration
PIN
24
MODE/
LRSEL
NAME
0 = Hardware control mode
1 = 3-wire serial control mode
Z = 2-wire serial control mode
DESCRIPTION
The software control interface may be
PD, Rev 4.2,August 2009
Production Data
The system
2
S interface
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