WM8281ECSSLASHR datasheet(44/392 Pages) CIRRUS

44 / 392 page

WM8281

Rev 4.0

The WM8281 is cost-optimised for a wide range of mobile phone applications, and features two

channels of Class D power amplification. For applications requiring more than two channels of power

amplification, the PDM output channels can be used to drive up to four external PDM-input speaker

drivers. In applications where stereo loudspeakers are physically widely separated, the PDM outputs

can ease layout and EMC by avoiding the need to run the Class-D speaker outputs over long

distances and interconnects.

DIGITAL AUDIO CORE

The WM8281 uses a core architecture based on all-digital signal routing, making digital audio effects

available on all signal paths, regardless of whether the source data input is analogue or digital. The

digital mixing desk allows different audio effects to be applied simultaneously on many independent

paths, whilst also supporting a variety of sample rates concurrently. This helps support many new

audio use-cases. Soft mute and un-mute control allows smooth transitions between use-cases without

interrupting existing audio streams elsewhere.

The Cirrus Logic Ambient Noise Cancellation (ANC) processor within the WM8281 provides the

capability to improve the intelligibility of a voice call by using destructive interference to reduce the

acoustic energy of the ambient sound. The stereo ANC capability supports a wide variety of

headset/handset applications.

The Cirrus Logic ANC technology supports receive (RX) path noise cancellation. Transmit (TX) path

noise reduction, and multi-mic Acoustic Echo Cancellation (AEC) algorithms are also supported. The

WM8281 is ideal for mobile telephony, providing enhanced voice communication quality for near-end

and far-end handset users.

The WM8281 digital core provides an extensive capability for programmable signal processing

algorithms. The DSP can support functions such as wind noise, side-tone and other programmable

filters. A wide range of application-specific filters and audio enhancements can also be implemented,

including Dynamic Range Control (DRC), Multi-band Compression (MBC), and Virtual Surround

Sound (VSS). These digital effects can be used to improve audibility and stereo imaging while

minimising supply current.

Highly flexible digital mixing, including mixing between audio interfaces, is possible. The WM8281

performs multi-channel full-duplex asynchronous sample rate conversion, providing use-case flexibility

across a broad range of system architectures. Automatic sample rate detection is provided, enabling

seamless wideband/narrowband voice call handover.

Dynamic Range Controller (DRC) functions are available for optimising audio signal levels. In

playback modes, the DRC can be used to maximise loudness, while limiting the signal level to avoid

distortion, clipping or battery droop, in particular for high-power output drivers such as speaker

amplifiers. In record modes, the DRC assists in applications where the signal level is unpredictable.

The 5-band parametric equaliser (EQ) functions can be used to compensate for the frequency

characteristics of the output transducers. EQ functions can be cascaded to provide additional

frequency control. Programmable high-pass and low-pass filters are also available for general filtering

applications such as removal of wind and other low-frequency noise.

DIGITAL INTERFACES

Three serial digital audio interfaces (AIFs) each support PCM, TDM and I2S data formats for

compatibility with most industry-standard chipsets. AIF1 supports eight input/output channels; AIF2

supports six input/output channels; AIF3 supports two input/output channels. Bidirectional operation at

sample rates up to 192kHz is supported.

Eight digital PDM input channels are available (four stereo interfaces); these are typically used for

digital microphones, powered from the integrated MICBIAS power supply regulators. Four PDM output

channels are also available (two stereo interfaces); these are typically used for external power

amplifiers. Embedded mute codes provide a control mechanism for external PDM-input devices.

The WM8281 features a MIPI-compliant SLIMbus interface, providing eight channels of audio

input/output. Mixed audio sample rates are supported on the SLIMbus interface. The SLIMbus

interface also supports read/write access to the WM8281 control registers.

The WM8281 is equipped with an I2C/SPI control interface and an I2C-only control interface. The I2C

slave port operates up to 3.4MHz; the SPI ports operate up to 26MHz. Full access to the register map

is also provided via the SLIMbus port.

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