wm8987 Wolfson Microelectronics plc, wm8987 Datasheet - Page 46

• Manufacturer Part Number: wm8987
• Description: Stereo Codec For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

WM8987L
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SAVING POWER BY REDUCING OVERSAMPLING RATE
The default mode of operation of the ADC and DAC digital filters is in 128x oversampling mode.
Under the control of ADCOSR and DACOSR the oversampling rate may be halved. This will result in
a slight decrease in noise performance but will also reduce the power consumption of the device. In
USB mode ADCOSR must be set to 0, i.e. 128x oversampling.
Table 43 ADC and DAC Oversampling Rate Selection
ADCOSR set to ‘1’, 64x oversample mode, is not supported in USB mode (USB=1).
SAVING POWER AT HIGHER SUPPLY VOLTAGES
The analogue supplies to the WM8987L can run from 1.8V to 3.6V. By default, all analogue circuitry
on the device is optimized to run at 3.3V. This set-up is also good for all other supply voltages down
to 1.8V. At lower voltages, performance can be improved by increasing the bias current. If low
power operation is preferred the bias current can be left at the default setting. This is controlled as
shown below.
R24 (18h)
Additional Control
(2)
R23 (17h)
Additional
Control(1)
REGISTER
ADDRESS
REGISTER
ADDRESS
7:6
BIT
1
0
VSEL
[1:0]
LABEL
BIT
ADCOSR
DACOSR
11
DEFAULT
LABEL
0
0
Analogue Bias optimization
00: Highest bias current, optimized for
AVDD=1.8V
01: Bias current optimized for AVDD=2.5V
1X: Lowest bias current, optimized for AVDD=3.3V
DEFAULT
DESCRIPTION
ADC oversample rate select
1 = 64x (lowest power)
0 = 128x (best SNR)
DAC oversample rate select
1 = 64x (lowest power)
0 = 128x (best SNR)
DESCRIPTION
PD Rev 4.0 August 2008
Production Data
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