WM8940
Pre-Production
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R56
7
MONOATTN
0
Attenuation control for bypass path
(output of input boost stage) to mono
mixer input
Mono mixer
control
0 = 0dB
1 = -10dB
0=No mute
6
MONOMUTE
0
1=Output muted. During mute the
mono output will output VMID which can
be used as a DC reference for a
headphone out.
2
1
0
AUX2MONO
BYP2MONO
DAC2MONO
0
0
0
Output of Auxilary amplifier to mono
mixer input:
0 = not selected
1 = selected
Bypass path (output of input boost
stage) to mono mixer input
0 = non selected
1 = selected
Output of DAC to mono mixer input
0 = not selected
1 = selected
Table 37 Mono Mixer Control
ENABLING THE OUTPUTS
Each analogue output of the WM8940 can be separately enabled or disabled. The analogue mixer
associated with each output has a separate enable. All outputs are disabled by default. To save
power, unused parts of the WM8940 should remain disabled.
Outputs can be enabled at any time, but it is not recommended to do so when BUFIO is disabled
(BUFIOEN=0), as this may cause pop noise (see “POP Minimisation” section).
REGISTER
ADDRESS
BIT
LABEL
BIASEN
DEFAULT
DESCRIPTION
R1
3
2
0
0
Analogue amplifiers bias enable
VMID buffer enable
Power
BUFIOEN
management 1
R3
7
6
5
3
2
MONOEN
SPKNEN
0
0
0
0
0
MONOOUT enable
SPKOUTN enable
SPKOUTP enable
Mono mixer enable
Speaker Mixer enable
Power
management 3
SPKPEN
MONOMIXEN
SPKMIXEN
Note: All “Enable” bits are 1 = ON, 0 = OFF
Table 38 Output Stages Power Management Control
UNUSED ANALOGUE INPUTS/OUTPUTS
Whenever an analogue input/output is disabled, it remains connected to AVDD/2 through a resistor.
This helps to prevent pop noise when the output is re-enabled. The resistance between the voltage
buffer and the output pins can be controlled using the VROI control bit. The default impedance is
low, so that any capacitors on the outputs can charge up quickly at start-up. If a high impedance is
desired for disabled outputs, VROI can then be set to 1, increasing the resistance to about 30kΩ.
Pre-Production, Rev 3.0, February 2007
46
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
