Pre-Production
WM8985
POWER MANAGEMENT
SAVING POWER BY REDUCING OVERSAMPLING RATE
The default mode of operation of the ADC and DAC digital filters is in 64x oversampling mode.
Under the control of ADCOSR128 and DACOSR128 the oversampling rate may be doubled. 64x
oversampling results in a slight decrease in noise performance compared to 128x but lowers the
power consumption of the device.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R10 (0Ah)
3
3
DACOSR128
0
DAC oversample rate select
0 = 64x (lowest power)
1 = 128x (best SNR)
DAC control
R14 (0Eh)
ADCOSR128
0
ADC oversample rate select
0 = 64x (lowest power)
1 = 128x (best SNR)
ADC control
Table 48 ADC and DAC Oversampling Rate Selection
LOW POWER MODE
If only DAC or ADC functionality is required, the WM8985 can be put into a low power mode. In this
mode, the DSP core runs at half of the normal rate, reducing digital power consumption of the core
by half. For DAC low power only, 3D enhancement with 2-Band equaliser functionality is permitted,
where only Band 1 (low shelf) and Band 5 (high shelf) can be used. For ADC low power, the
equaliser and 3D cannot be used.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R7 (07h)
Additional Ctrl
Table 49 DSP Core Low Power Mode Control
8
M128ENB
0
0 = low power mode enabled
1 = low power mode disabled
There are 3 modes of low power operation, as detailed below. The device will not enter low power
unless in one of these register configurations, regardless of M128ENB.
For pop-free operation of the device it is recommended to change the M128ENB low power
functionality only when both the DACs and ADCs are disabled, i.e. when DACENL=0, DACENR=0,
ADCENL=0 and ADCENR=0.
FUNCTION
REGISTER BITS
M128ENB
ADCENL
SETTING
DESCRIPTION
ADC low power
0
1
1
0
0
Either or both of ADCENL and
ADCENR must be set (mono or
stereo mode)
ADCENR
DACENL
DACENR
EQ3DMODE
M128ENB
ADCENL
1 (DAC path)
DAC low power
0
0
0
1
1
Either or both of DACENL and
DACENR must be set (mono or
stereo mode)
ADCENR
DACENL
EQ3DMODE = 0: EQ in ADC path
EQ3DMODE = 1: EQ in DAC path
DACENR
Table 50 DSP Core Low Power Modes for ADC Only and DAC Only Modes
PP, Rev 3.4, October 2006
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
