WM8940 Wolfson Microelectronics Ltd., WM8940 Datasheet - Page 46

• Manufacturer Part Number: WM8940
• Description: Mono Codec with Speaker Driver
• Manufacturer: Wolfson Microelectronics Ltd.

WM8940
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Table 37 Mono Mixer Control
ENABLING THE OUTPUTS
Table 38 Output Stages Power Management Control
UNUSED ANALOGUE INPUTS/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).
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.
R56
Mono mixer
control
R1
Power
management 1
R3
Power
management 3
Note: All “Enable” bits are 1 = ON, 0 = OFF
REGISTER
ADDRESS
REGISTER
ADDRESS
3
2
7
6
5
3
2
BIT
BIT
7
6
2
1
0
BIASEN
BUFIOEN
MONOEN
SPKNEN
SPKPEN
MONOMIXEN 0
SPKMIXEN
MONOATTN
MONOMUTE
AUX2MONO
BYP2MONO
DAC2MONO
LABEL
LABEL
0
0
0
0
0
0
DEFAULT
DEFAULT
0
0
0
0
0
Analogue amplifiers bias enable
VMID buffer enable
MONOOUT enable
SPKOUTN enable
SPKOUTP enable
Mono mixer enable
Speaker Mixer enable
Pre-Production, Rev 3.0, February 2007
Attenuation control for bypass path
(output of input boost stage) to mono
mixer input
0=No mute
1=Output muted. During mute the
mono output will output VMID which can
be used as a DC reference for a
headphone out.
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
0 = 0dB
1 = -10dB
DESCRIPTION
DESCRIPTION
Pre-Production
46