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DESCRIPTION
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.
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.
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.
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).
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WM8731 / WM8731L
Portable Internet Audio CODEC with Headphone Driver
and Programmable Sample Rates
FEATURES
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-lead SSOP or 28-lead QFN package
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APPLICATIONS
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MODE
SCLK
Portable MP3 Players and Recorders
CD and Minidisc Recorders
PDAs / smartphones
BLOCK DIAGRAM
CSB
AVDD
CONTROL INTERFACE
VMID
Bypass
MUTE
SDIN
W
WM8731
HPVDD
HPGND
+6 to -73dB
1 dB Steps
VOL/
MUTE
H/P
DRIVER
AGND
ATTEN/
MUTE
MICBIAS
RLINEIN
VOL
MUTE
MUTE
MUX
Side Tone
RHPOUT
ADC
DAC
MUTE
+12 to -34.5dB, 1.5dB
Steps
MICIN
0dB/
20dB
Σ
ROUT
DIGITAL
FILTERS
LOUT
MUTE
MUX
ADC
DAC
MUTE
LLINEIN
VOL
MUTE
Σ
VOL/
MUTE
H/P
DRIVER
+12 to -34.5dB, 1.5dB
Steps
LHPOUT
Side Tone
ATTEN/
MUTE
MUTE
CLKIN
DIVIDER
(Div x1, x2)
CLKOUT
DIVIDER
(Div x1, x2)
+6 to -73dB
1 dB Steps
OSC
DIGTAL AUDIO INTERFACE
Bypass
DACLRC
ADCLRC
DCVDD
CLKOUT
DACDAT
XTI/MCLK
ADCDAT
DBVDD
WOLFSON MICROELECTRONICS plc
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DGND
BCLK
XTO
Production Data, August 2006, Rev 4.3
Copyright
©2006
Wolfson Microelectronics plc
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
