WM8951L_07 Datasheet, PDF (14/42 Pages) Wolfson Microelectronics plc – Stereo ADC with Microphone Input and Clock Generator

WM8951L
Production Data
DEVICE DESCRIPTION
INTRODUCTION
The WM8951L is a low power stereo audio ADC designed specifically for portable audio products. It’s
features, performance and low power consumption make it ideal for portable voice recorders, games
console accessories and wireless microphones.
The WM8951L includes line and microphone inputs to the on-board ADC, a crystal oscillator,
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 ADC includes three low noise inputs - mono microphone and stereo line. Line inputs have +12dB
to -34dB logarithmic volume level adjustments and mute. The Microphone input has -6dB to 34dB
volume level adjustment. An electret microphone bias level is also available. All the required input
filtering is contained within the device with no external components required.
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 design of the WM8951L has given much attention to power consumption without compromising
performance. It includes the ability to power off selective parts of the circuitry under software control,
thus conserving power. Power saving modes be configured under software control including a
standby and power off mode.
The device caters for a number of different sampling rates including industry standard 8kHz, 32kHz,
44.1kHz, 48kHz, 88.2kHz and 96kHz.
The digitised output is available in a number of audio data formats I²S, 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 2 or 3-wire MPU interface.
A crystal oscillator is included on board the device. The device can generate the system master clock
or alternatively it can accept an external master clock from the audio system.
AUDIO SIGNAL PATH
LINE INPUTS
The WM8951L 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 ADC input mute.
The scheme is illustrated in Figure 9. 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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PD Rev 4.1 December 2007
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