Pre Production
WM8941
INPUT BOOST
The input BOOST circuit has 3 selectable inputs: the input microphone PGA output, the AUX
amplifier output and the MICP input pin (when not using a differential microphone configuration).
These three inputs can be mixed together and have individual gain boost/adjust as shown in Figure
8.
Figure 8 Input Boost Stage
The input PGA path can have a +20dB boost (PGABOOST=1) a 0dB pass through (PGABOOST=0)
or be completely isolated from the input boost circuit (INPPGAMUTE=1).
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R45
6
8
INPPGAMUTE
1
Mute control for input PGA:
Input PGA gain
control
0=Input PGA not muted, normal operation
1=Input PGA muted (and disconnected from
the following input BOOST stage).
R47
PGABOOST
0
0 = PGA output has +0dB gain through
input BOOST stage.
Input BOOST
control
1 = PGA output has +20dB gain through
input BOOST stage.
Table 6 Input BOOST Stage Control
The Auxiliary amplifier path to the BOOST stage is controlled by the AUX2BOOSTVOL[2:0] register
bits. When AUX2BOOSTVOL=000 this path is completely disconnected from the BOOST stage.
Settings 001 through to 111 control the gain in 3dB steps from -12dB to +6dB.
The MICP path to the BOOST stage is controlled by the MICP2BOOSTVOL[2:0] register bits.
When MICP2BOOSTVOL=000 this input pin is completely disconnected from the BOOST stage.
Settings 001 through to 111 control the gain in 3dB steps from -12dB to +6dB.
PP, Rev 3.3, December 2007
23
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
