WM8955BLGECOSLASHV datasheet(16/44 Pages) WOLFSON

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WM8955BL

Production Data

PD Rev 4.1 February 2007

DEVICE DESCRIPTION

INTRODUCTION

The WM8955BL is a low power audio DAC offering a combination of high quality audio, advanced

features, low power and small size. These characteristics make it ideal for portable digital audio

applications such as portable music players and smartphones.

The device has a configurable digital audio interface where digital audio data is fed to the internal

digital filters and then the DAC. The interface supports a number of audio data formats including I

2S,

DSP Mode (a burst mode in which frame sync plus 2 data packed words are transmitted), Left

Justified and Right Justified formats, and can operate in master or slave modes.

The on-chip digital filters perform tone control and digital volume control according to the user setting,

and convert the audio data into oversampled bitstreams, which are passed to the left and right

channel DACs. A multi-bit, low-order

ΣΔ DAC architecture with dynamic element matching is used,

delivering optimum performance with low power consumption.

The DAC output signal enters an analogue mixer where analogue input signals can be added to it.

The WM8955BL has a total of six analogue output pins, which can be configured as stereo line-outs,

mono line-outs, differential mono line-outs, stereo headphone outputs or differential mono (BTL)

earpiece outputs.

The WM8955BL includes an on-chip PLL to generate commonly used audio rates, such as 48kHz

and 44.1kHz, from system clocks found in GSM, CDMA and PDC phones and other portable

systems.

To allow full software control over all its features, the WM8955BL offers a choice of 2 or 3 wire MPU

control interface. It is fully compatible and an ideal partner for a wide range of industry standard

microprocessors, controllers and DSPs.

The design of the WM8955BL has given much attention to power consumption without compromising

performance. It operates at very low voltages, and includes the ability to power off parts of the

circuitry under software control, including standby and power off modes.

SIGNAL PATH

The WM8955BL signal paths consists of digital filters, DACs, analogue mixers and output drivers.

Each circuit block can be enabled or disabled separately using the control bits in register 26 (see

“Power Management”). Thus it is possible to utilise the analogue mixing and amplification provided by

the WM8955BL, irrespective of whether the DACs are running or not.

The WM8955BL receives digital input data on the DACDAT pin. The digital filter block processes the

data to provide the following functions:

•

Digital volume control

•

Tone control and Bass Boost

•

Digital Mono Mix

•

Sigma-Delta Modulation

Two high performance, sigma-delta audio DACs convert the digital data into two analogue signals

(left and right). These can then be mixed with analogue signals from the LINEINL, LINEINR and

MONOIN pins, and the mix is fed to the output drivers, LOUT1/ROUT1, LOUT2/ROUT2, MONOOUT

and OUT3.

•

LOUT1/ROUT1: can drive 16

Ω or 32Ω stereo headphones or stereo line output.

•

LOUT2/ROUT2: can drive a 32

Ω earpiece, stereo headphones or a stereo line-out.

•

MONOOUT: line output designed to drive a 10k

Ω load.

•

OUT3: multi-function output, may be used for capacitor-less headphone drive, differential

mono-out, line-out or 32

Ω earpiece driver.

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