WM8731 / WM8731L
Portable Internet Audio CODEC with Headphone Driver
and Programmable Sample Rates
DESCRIPTION
FEATURES
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The WM8731 or WM8731L (WM8731/L) are low power
stereo CODECs with an integrated headphone driver. The
WM8731/L is designed specifically for portable MP3 audio
and speech players and recorders. The WM8731 is also
ideal for MD, CD-RW machines and DAT recorders.
Highly Efficient Headphone Driver
Audio Performance
- ADC SNR 90dB (‘A’ weighted) at 3.3V, 85dB at 1.8V
DAC SNR 100dB (‘A’ weighted) at 3.3V, 95dB at 1.8V
Low Power
- Playback only 22mW, 8mW (‘L’ Variant)
- Analogue Pass Through 12mW, 3.5mW (‘L’ variant)
- 1.42 – 3.6V Digital Supply Operation
- 2.7 – 3.6V Analogue Supply Operation
- 1.8 – 3.6V Analogue Supply Operation (‘L’ Variant)
ADC and DAC Sampling Frequency: 8kHz – 96kHz
Selectable ADC High Pass Filter
2 or 3-Wire MPU Serial Control Interface
Programmable Audio Data Interface Modes
2
- I S, Left, Right Justified or DSP
- 16/20/24/32 bit Word Lengths
- Master or Slave Clocking Mode
Microphone Input and Electret Bias with Side Tone Mixer
Available in 28-Pin SSOP or 28-pin QFN package
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Stereo line and mono microphone level audio inputs are
provided, along with a mute function, programmable line
level volume control and a bias voltage output suitable for
an electret type microphone.
Stereo 24-bit multi-bit sigma delta ADCs and DACs are
used with oversampling digital interpolation and decimation
filters. Digital audio input word lengths from 16-32 bits and
sampling rates from 8kHz to 96kHz are supported.
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Stereo audio outputs are buffered for driving headphones
from a programmable volume control, line level outputs are
also provided along with anti-thump mute and power
up/down circuitry.
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The device is controlled via a 2 or 3 wire serial interface.
The interface provides access to all features including
volume controls, mutes, de-emphasis and extensive power
management facilities. The device is available in a small 28pin SSOP package or the smaller 28 lead quad flat leadless
package (QFN).
APPLICATIONS
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Portable MP3 Players and Recorders
CD and Minidisc Recorders
PDAs / smartphones
SCLK
MODE
SDIN
CSB
BLOCK DIAGRAM
AVDD
W
WM8731
CONTROL INTERFACE
VMID
HPVDD
Bypass
MUTE
AGND
+6 to -73dB
1 dB Steps
Side Tone
MICBIAS
RLINEIN
HPGND
ATTEN/
MUTE
VOL
MUTE
+12 to -34.5dB, 1.5dB
Steps
MUTE
ADC
MUX
DAC
H/P
DRIVER
RHPOUT
Σ
ROUT
DIGITAL
FILTERS
0dB/
20dB
MICIN
MUTE
VOL/
MUTE
LOUT
MUTE
LLINEIN
DAC
ADC
MUX
MUTE
MUTE
VOL
Σ
VOL/
MUTE
+12 to -34.5dB, 1.5dB
Steps
Side Tone
H/P
DRIVER
LHPOUT
+6 to -73dB
1 dB Steps
ATTEN/
MUTE
MUTE
DGND
DBVDD
Bypass
DCVDD
ADCDAT
ADCLRC
BCLK
DACLRC
DIGTAL AUDIO INTERFACE
DACDAT
XTI/MCLK
XTO
CLKOUT
DIVIDER
(Div x1, x2)
CLKOUT
CLKIN
DIVIDER
(Div x1, x2)
OSC
WOLFSON MICROELECTRONICS plc
Production Data, January 2002, Rev 3.3
www.wolfsonmicro.com
Copyright 2003 Wolfson Microelectronics plc
