WM8734 datasheet(16/46 Pages) WOLFSON

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WM8734

Production Data

PD Rev 4.1 November 2006

DEVICE DESCRIPTION

The WM8734 is a high performance audio CODEC designed specifically for audio applications that

require recording and playback features.

The CODEC includes line inputs to the on-board ADC, line outputs from the on-board DAC, a

configurable digital audio interface and a choice of 2 or 3 wire MPU control interface. It is fully

compatible and an ideal partner for a range of industry standard microprocessors, controllers and

DSPs.

The CODEC includes a stereo low noise input. Line inputs have +12dB to -34dB logarithmic volume

level adjustments and mute. All the required input filtering is contained within the device.

The on-board stereo analogue to digital converter (ADC) is of a high quality using a multi-bit high-

order oversampling architecture delivering optimum performance with low power consumption. The

output from the ADC is available on the digital audio interface. The ADC includes an optional digital

high pass filter to remove unwanted dc components from the audio signal.

The on-board digital to analogue converter (DAC) accepts digital audio from the digital audio

interface. Digital filter de-emphasis at 32kHz, 44.1kHz and 48kHz can be applied to the digital data

under software control. The DAC employs a high quality multi-bit high-order oversampling

architecture to again deliver optimum performance with low power consumption.

Special techniques allow the audio to be muted and the device safely placed into standby, sections

of the device powered off and volume levels adjusted without any audible clicks, pops or zipper

noises. Therefore standby and power off modes may be used dynamically under software control,

whenever recording or playback is not required.

The device caters for a number of different sampling rates including industry standard 8kHz, 32kHz,

44.1kHz, 48kHz, 88.2kHz and 96kHz. The digital filters used for both record and playback are

optimised for each sampling rate used.

The digitised output is available in a number of audio data formats I

2S, DSP Mode (a burst mode in

which frame sync plus 2 data packed words are transmitted), MSB-First, left justified and MSB-First,

right justified. The digital audio interface can operate in both master or slave modes.

The software control uses either a 2 or 3-wire MPU interface.

AUDIO SIGNAL PATH

LINE INPUTS

The WM8734 provides Left and Right channel line inputs (RLINEIN and LLINEIN). The inputs are

high impedance and low capacitance, thus ideally suited to receiving line level signals from external

hi-fi or audio equipment.

Both line inputs include independent programmable volume level adjustments and input mute. The

scheme is illustrated in Figure 8. Passive RF and active Anti-Alias filters are also incorporated within

the line inputs. These prevent high frequencies aliasing into the audio band or otherwise degrading

performance.

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