WM8731 / WM8731L
Portable Internet Audio CODEC with Headphone Driver
and Programmable Sample Rates
DESCRIPTION
FEATURES
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Highly Efficient Headphone Driver
Audio Performance
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.
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ADC SNR 90dB (‘A’ weighted) at 3.3V, 85dB at 1.8V
DAC SNR 100dB (‘A’ weighted) at 3.3V, 95dB at 1.8V
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Low Power
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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)
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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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
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I2S, Left, Right Justified or DSP
16/20/24/32 bit Word Lengths
Master or Slave Clocking Mode
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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Microphone Input and Electret Bias with Side Tone Mixer
Available in 28-Pin SSOP or 28-pin QFN package
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 28-
pin 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
BLOCK DIAGRAM
AVDD
W
CONTROL INTERFACE
WM8731
VMID
HPVDD
HPGND
Bypass
MUTE
AGND
ATTEN/
MUTE
+6 to -73dB
1 dB Steps
Side Tone
H/P
DRIVER
MICBIAS
RLINEIN
VOL/
RHPOUT
MUTE
VOL
MUTE
MUTE
MUTE
ADC
ADC
MUX
DAC
DAC
Σ
Σ
+12 to -34.5dB, 1.5dB
Steps
ROUT
LOUT
0dB/
20dB
DIGITAL
FILTERS
MICIN
MUTE
MUTE
MUX
MUTE
VOL
LLINEIN
VOL/
MUTE
H/P
DRIVER
LHPOUT
+12 to -34.5dB, 1.5dB
Steps
Side Tone
+6 to -73dB
1 dB Steps
ATTEN/
MUTE
MUTE
CLKIN
DIVIDER
CLKOUT
DIVIDER
DIGTAL AUDIO INTERFACE
Bypass
OSC
(Div x1, x2)
(Div x1, x2)
Production Data, January 2002, Rev 3.3
Copyright 2003 Wolfson Microelectronics plc
WOLFSON MICROELECTRONICS plc
www.wolfsonmicro.com