WM8993 datasheet(33/229 Pages) WOLFSON

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Production Data

WM8993

PD, November 2010, Rev 4.0

DEVICE DESCRIPTION

INTRODUCTION

The WM8993 is a low power, high quality audio codec designed to interface with a wide range of

processors and analogue components. A high level of mixed-signal integration in a very small

3.64 x 3.54mm footprint makes it ideal for portable applications such as mobile phones.

Eight highly flexible analogue inputs allow interfacing to up to four microphone inputs (single-ended

or differential), plus multiple stereo or mono line inputs. Connections to an external voice CODEC,

FM radio, melody IC, line input, handset MIC and headset MIC are all fully supported. Signal routing

to the output mixers and within the CODEC has been designed for maximum flexibility to support a

wide variety of usage modes. A ‘Direct Voice’ path from a voice CODEC directly to the Speaker or

Earpiece output drivers is included.

Nine analogue output drivers are integrated, including a stereo pair of high power, high quality

Class D/AB switchable speaker drivers; these can support 1W each in stereo mode, or can be

coupled to support a 2W mono speaker output. A mono earpiece driver is provided, providing output

from the output mixers or from the low-power differential ‘Direct Voice’ path.

One pair of ground-reference headphone outputs is provided; these are powered from an integrated

Charge Pump, enabling high quality, power efficient headphone playback without any requirement for

DC blocking capacitors. A DC Servo circuit is available for DC offset correction, thereby suppressing

pops and reducing power consumption. Four line outputs are provided, with multiple configuration

options including 4 x single-ended output or 2 x differential outputs. The line outputs are suitable for

output to a voice CODEC or an external speaker driver. They are also capable of driving ear

speakers and stereo headsets. Ground loop feedback is available on the headphone outputs and the

line outputs, providing rejection of noise on the ground connections. All outputs have integrated pop

and click suppression features.

Internal differential signal routing and amplifier configurations have been optimised to provide the

lowest possible power consumption for a wide range of usage scenarios, including voice calls and

music playback. The speaker drivers offer low leakage and high PSRR; this enables direct

connection to a Lithium battery. The speaker drivers provide eight levels of AC and DC gain to allow

output signal levels to be maximised for many commonly-used SPKVDD/AVDD1 combinations.

The stereo ADCs and DACs are of hi-fi quality, using a 24-bit low-order oversampling architecture to

deliver optimum performance. A flexible clocking arrangement supports mixed ADC and DAC sample

rates, whilst an integrated ultra-low power FLL provides additional flexibility. A high pass filter is

available in the ADC path for removing DC offsets and suppressing low frequency noise such as

mechanical vibration and wind noise. A digital mixing path from the ADC to the DAC provides a

sidetone of enhanced quality during voice calls. DAC soft mute and un-mute is available for pop-free

music playback.

The integrated Dynamic Range Controller (DRC) and ReTuneTM Mobile 5-band parametric equaliser

(EQ) provide further processing capability of the digital audio paths. The DRC provides compression

and signal level control to improve the handling of unpredictable signal levels. ‘Anti-clip’ and ‘quick

release’ algorithms improve intelligibility in the presence of transients and impulsive noises. 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 WM8993 has a highly flexible digital audio interface, supporting a number of protocols, including

I2S, 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

μ-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.

The system clock (CLK_SYS) provides clocking for the ADCs, DACs, DSP core, digital audio

interface and other circuits. CLK_SYS can be derived directly from the MCLK pin or via an integrated

FLL, providing flexibility to support a wide range of clocking schemes. Typical portable system MCLK

frequencies, and sample rates from 8kHz to 48kHz are all supported. Automatic configuration of the

clocking circuits is available, derived from the sample rate and from the MCLK / CLK_SYS ratio.

The integrated FLL can be used as a free-running oscillator, enabling autonomous clocking of the

Class D drivers, Headphone Charge Pump and DC Servo if required. (Note that hi-fi ADC / DAC

operation requires an external crystal.)

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