WM8731 / WM8731L
w
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-lead SSOP or 28-lead 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-
lead 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
MUX
ADC
ADC
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
CLKOUT
DIVIDER
CLKIN
DIVIDER
Bypass
DIGTAL AUDIO INTERFACE
OSC
(Div x1, x2)
(Div x1, x2)
Production Data, August 2006, Rev 4.3
WOLFSON MICROELECTRONICS plc
Copyright ©2006 Wolfson Microelectronics plc
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