WM1811A datasheet(57/328 Pages) WOLFSON

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WM1811A

PD, November 2013, Rev 4.1

DIGITAL CORE ARCHITECTURE

The WM1811A Digital Core provides an extensive set of mixing and signal processing features. The

Digital Core Architecture is illustrated in Figure 17, which also identifies the datasheet sections

applicable to each portion of the Digital Core.

The digital audio interfaces AIF1 and AIF2 each support one stereo pair of input and output signal

paths through the WM1811A DSP functions. The signal mixing for the AIF1 and AIF2 output paths is

described in “Audio Interface 1 (AIF1) Output Digital Mixing” and “Audio Interface 2 (AIF2) Output

Digital Mixing” respectively.

A digital mixing path from the ADCs or Digital Microphones to the DAC and AIF2 output paths

provides a high quality sidetone for voice calls or other applications. The sidetone filter and volume

controls are described in “Digital Sidetone Volume and Filter Control”.

Each of the DACs has a dedicated mixer for controlling the signal paths to that DAC. The

configuration of these signal paths is described in “DAC Output Digital Mixing”. A similar pair of mixers

is provided for controlling the signal paths to the AIF2 output channels, as described in “Audio

Interface 2 (AIF2) Output Digital Mixing”.

The DAC and AIF2 output signal paths are each provided with digital volume control andsoft mute /

un-mute features. The associated controls are defined in the “Digital Volume (DAC and AIF2 Output

Paths)” and the “Digital Volume Soft Mute and Soft Un-Mute” sections.

Digital signal processing can be applied to the input and output signal paths. The available features

include 5-band equalization (EQ), 3D stereo expansion and dynamic range control (DRC).

The EQ provides the capability to tailor the audio path according to the frequency characteristics of an

earpiece or loudspeaker, and/or according to user preferences. The EQ controls are described in

“ReTune

TM Mobile Parametric Equalizer (EQ)”.The DRC provides adaptive signal level control to

improve the handling of unpredictable signal levels and to improve intelligibility in the presence of

transients and impulsive noises. The DRC controls are described in “Dynamic Range Control (DRC)”.

3D stereo expansion provides a stereo enhancement effect; the depth of the effect is programmable,

as described in “3D Stereo Expansion”.

The input signal paths are also equipped with digital volume control and soft mute / un-mute control;

see “Digital Volume and Filter Control” for details of these features.

The output signal paths are equipped with digital volume control and a programmable high-pass filter

(HPF). The Dynamic Range Control (DRC) circuit can also be applied here, with the restriction that a

DRC cannot be enabled in the input and output path of one AIF channel at the same time. The AIF

output volume and filter controls are described in “Digital Volume and Filter Control”.

The WM1811A provides an ultrasonic mode on the output paths of AIF1, allowing high frequency

signals (such as ultrasonic microphone signals) to be output. See “Ultrasonic (4FS) AIF Output Mode”

for further details.

The WM1811A provides two full audio interfaces, AIF1 and AIF2. Each interface supports a number of

protocols, including I

2S, DSP, MSB-first left/right justified, and can operate in master or slave modes.

PCM operation is supported in the DSP mode. A-law and

-law companding are also supported. Time

division multiplexing (TDM) is available to allow multiple devices to stream data simultaneously on the

same bus, saving space and power.

Two-channel input and output is supported on AIF1 and on AIF2. A third interface, AIF3, is partially

supported, using multiplexers to re-configure alternate connections to AIF1 or AIF2.

Signal mixing between audio interfaces is possible. The WM1811A performs stereo full-duplex sample

rate conversion between the audio interfaces as required.

The audio interfaces AIF1, AIF2 and AIF3 are referenced to DBVDD1, DBVDD2 and DBVDD3

respectively; this provides additional capability to interface between different sub-systems within an

application.

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