WM8850 datasheet(28/223 Pages) WOLFSON

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WM8850

Pre-Production

PP, April 2011, Rev 3.2

INTRODUCTION

The WM8850 is a high performance multi-channel audio CODEC designed for high performance PC

audio systems.

The device offers full compatibility with the Intel High Definition Audio (HDA)

specification revision 1.0, allowing seamless integration with industry-standard HDA controllers.

The WM8850 has three high performance stereo DACs to enable six channels of high definition

audio, ideal for 5.1 channel applications. A high-performance ground-referenced stereo headphone

amplifier utilises advanced charge pump and DC servo technology to minimise system cost and

space without compromise on audio quality. Two stereo pairs of line outputs are also provided.

These line outputs may be used at the output of the PC to enable connection to a 5.1 speaker

system, or may be used connected to external speaker drivers in a notebook or netbook application.

The WM8850 also has two high performance stereo ADCs to provide Hi-Fi quality analogue line-in

and microphone input digitisation. A low noise microphone bias with programmable output voltage is

provided, ideally suited as a bias current source for ECM microphones. Additionally, the CODEC

contains a digital microphone interface capable of supporting up to four independent digital

microphones, allowing high quality microphone array implementations to be realised. One differential

stereo input is provided for line level signals, while one pseudo-differential stereo input with integrated

microphone preamplifier is provided.

The WM8850 also contains a S/PDIF transceiver which is fully compatible with IEC-60958-3. The

S/PDIF receive and transmit paths each contain a sample rate converter (SRC) to enable

asynchronous sample rate conversion between the S/PDIF receive/transmit and HDA interface clock

domains. An additional S/PDIF transmitter is provided to allow direct output of a stereo stream from

the HDA interface.

The WM8850 includes an integrated beep generator allowing system beeps to be played back

through the output paths.

This datasheet assumes familiarity with the High Definition Audio Specification Revision 1.0, available

from http://www.intel.com/standards/hdaudio/. For those verbs implemented in the WM8850 which

are as defined in the High Definition Audio Specification Revision 1.0 there is no detailed text

describing their use in this datasheet. However, detailed text describing the function of of vendor-

specific verbs is provided. Additionally, a full list of each node and each verb implemented in the

WM8850 is provided at the rear of the document.

WOLFSON INTERPRETATION OF HDA SPECIFICATION

DOLBY AC3 (IEC-61937)

The AFG node and Converter Widget nodes have a parameter called AC3 within the Supported

Stream Formats Parameter. The Intel High Definition Audio specification states that AC3 should be

set to 1 if the node supports Dolby AC3 (IEC-61937) encoded data.

There is some ambiguity as to what is meant by “supports Dolby AC3 (IEC-61937)”. The WM8850

does not support processing of Dolby AC3 (IEC-61937) encoded data but it does support the passing

of AC3 data through the S/PDIF Converter Widgets.

Wolfson interpret the Intel specification to mean that the AC3 parameter should be set if a node

supports the encoding/decoding of AC3 data, and so we set the WM8850 AC3 parameters to 0.

When the S/PDIF Converters are passing AC3 (IEC-61937) data, the Stream Format Verb for the

widget node should have Bits = 1 (for 16-bit formatting) and Type = 1 to indicate that non-PCM data is

being passed. Note that setting Type is for controller purposes only, and the WM8850 performs the

same operation regardless of what Type is set to.

The user should ensure that Sample Rate Converters (SRCs) are bypassed when S/PDIF contains

AC3 data.

FLOAT32

The WM8850 performs a Fixed-point/Floating-point conversion. Fixed point format is <1,23>, while

floating point format is IEEE-754, single precision 32-bit, full scale between -1.0 and 1.0 with silence

at 0.0.

WM8850 Datasheet(PDF) 28 Page - Wolfson Microelectronics plc

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