WM8737 datasheet(14/38 Pages) WOLFSON

14 / 38 page

WM8737L

Preliminary Technical Data

AI Rev 3.0 May 2004

DEVICE DESCRIPTION

INTRODUCTION

The WM8737L is a low power analogue to digital converter (ADC) designed for audio recording. Its

features, performance and low power consumption make it ideal for recordable CD players, MP3

players, portable MD players and PDAs.

The device includes three stereo analogue inputs with a multiplexer to select between inputs. Each

input can be used as either a line level input or as a microphone input with on-chip microphone pre-

amplifiers. A programmable gain amplifier provides additional gain or attenuation, and can be used

for automatic level control (ALC), keeping the recording volume constant. It is also possible to use

the WM8737L as a mono device, or to mix the two channels to mono, either in the analogue or in the

digital domain.

The ADC is of a high quality using a multi-bit high-order oversampling architecture delivering high

SNR at low power consumption. It can operate at oversampling rates of 64fs (low power mode) or

128fs (normal power mode), allowing users to design for low power consumption or high

performance. The ADC also includes a digital high pass filter to remove unwanted DC components

from the audio signal. This filter may be turned off for DC measurements.

The output from the ADC is available on a configurable digital audio interface. It supports a number

of audio data formats including I

2S, DSP Mode, Left justified and Right justified, and can operate in

master or slave modes.

The WM8737L 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, 24kHz, 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.

The WM8737L can be controlled through a 2 wire 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 design of the WM8737L has minimised power consumption without compromising performance.

It can operate at very low voltages, can power off parts of the circuitry under software control and

includes standby and power off modes.

INPUT SIGNAL PATH

The signal path consists of a multiplexer switch to select between three sets of analogue inputs,

followed by a microphone boost preamplifier with selectable gain settings of 13dB, 18dB, 28dB and

33dB.

The microphone preamplifier feeds into a PGA (programmable gain amplifier) via an external

capacitor which removes dc offsets that could otherwise produce zipper noise when the PGA gain

changes. Alternatively, for line input signals, the microphone preamplifier can be bypassed to reduce

power consumption and noise. The PGA gain can be controlled either by the user or by the on-chip

ALC function (see Automatic Level Control).

The output signal from each PGA (left and right) enters an ADC where it is digitised. The two

channels can also be mixed in the analogue domain and digitised in one ADC while the other ADC is

switched off to reduce power consumption (see “Power Management” section). The mono-mix signal

appears on both digital output channels.

LEFT AND RIGHT CHANNEL SIGNAL INPUTS

The WM8737L has two sets of low capacitance ac coupled analogue inputs, LINPUT1, LINPUT2,

LINPUT3 and RINPUT1, RINPUT2, RINPUT3. The LINSEL and RINSEL control bits select between

them. These inputs can be configured as microphone or line inputs by enabling or disabling the

microphone preamplifier. All inputs have high impedance when the preamplifier is used and their

impedance is between 1.8k

Ω and 50kΩ (depending on PGA gain) if the preamplifier is bypassed.

The signal inputs are internally high-impedance biased to the reference voltage, VREF. Whenever

line inputs are muted or the device is placed into standby mode 2 (see “Power Management”

section), the inputs stay biased to VREF. This reduces any audible clicks that may otherwise be

heard when changing inputs or awakening from standby.

WM8737 датащи(PDF) 14 Page - Wolfson Microelectronics plc

WM8737 датащи(HTML) 14 Page - Wolfson Microelectronics plc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

датащи скачать

ссылки URL