WM8950 datasheet(16/60 Pages) CIRRUS

16 / 60 page

WM8950

Rev 4.5

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

To ADC input

and output

mixers

AUX2BOOSTVOL=000

MICP2BOOSTVOL=000

Output from

AUX amp

Output from

input PGA

MICP

AUX2BOOSTVOL

R47[2:0]

MICP2BOOSTVOL

R47[6:4]

INPPGAMUTE

R45[6]

PGABOOST

R47[8]

-12dB to + 6dB

0dB or +20dB

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).

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R45

Input PGA gain

control

INPPGAMUTE

Mute control for input PGA:

0=Input PGA not muted, normal operation

1=Input PGA muted (and disconnected from

the following input BOOST stage).

R47

Input BOOST

control

PGABOOST

0 = PGA output has +0dB gain through input

BOOST stage.

1 = PGA output has +20dB gain through

input BOOST stage.

Table 3 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.

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