WM8751L Просмотр технического описания (PDF) - Wolfson Microelectronics plc

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WM8751L

Stereo DAC For Portable Audio Applications

Wolfson Microelectronics plc 

WM8751L

DEVICE DESCRIPTION

Production Data

INTRODUCTION

The WM8751L 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 I2S,

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 Σ∆ 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 WM8751L 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)

speaker outputs.

The WM8751L master clock can be either an industry standard 256/384 fs clock or a 12MHz/24MHz

USB clock. Sample rates of 8kHz, 11.025kHz, 12kHz, 16kHz, 22.05kHz, 32kHz, 44.1kHz, 48kHz,

88.2kHz and 96kHz can be generated directly from the master clock, without an external PLL. The

digital filters are optimised for each sample rate.

To allow full software control over all its features, the WM8751L 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 WM8751L 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 WM8751L 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 WM8751L, irrespective of whether the DACs are running or not.

The WM8751L 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, and

MONOOUT.

• LOUT1/ROUT1: can drive 16Ω or 32Ω stereo headphones or stereo line output.

• LOUT2/ROUT2: can drive an 8Ω mono speaker, stereo headphones or a stereo line-out.

• MONOOUT: line output designed to drive a 10kΩ load.

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

mono-out, line-out or 32Ω earpiece driver.

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PD Rev 4.2 August 2006

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