WM8976 datasheet(27/83 Pages) WOLFSON

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Preliminary Technical Data

WM8976

PTD Rev 2.0 February 2005

AUXILLIARY INPUTS

There are two auxilliary inputs, AUXL and AUXR which can be used for a variety of purposes such

as stereo line inputs or as a ‘beep’ input signal to be mixed with the outputs.

The AUXL input can be used as a line input to the input BOOST stage which has gain adjust of -

12dB to +6dB in 3dB steps (plus off). See the INPUT BOOST section for further details.

The AUXL/R inputs can also be mixed into the output channel mixers, with a gain of -15dB to +6dB

plus off.

In addition the AUXR input can be summed into the Right speaker output path (ROUT2) with a gain

adjust of -15 to +6dB. This allows a ‘beep’ input to be output on the speaker outputs only without

affecting the headphone or lineout signals.

INPUT BOOST

The stereo input PGA stage is followed by an input BOOST circuit. The input BOOST circuit has 3

selectable inputs: the input microphone PGA output, the AUX amplifier output and the L2 input pin

(can be used as a line input, bypassing the input PGA). These three inputs can be mixed together

and have individual gain boost/adjust as shown in Figure 12.

Figure 12 Input Boost Stage

The input PGA path can have a +20dB boost (PGABOOSTL=1), a 0dB pass through

(PGABOOSTL=0) or be completely isolated from the input boost circuit (INPPGAMUTEL=1).

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R47

Input BOOST

control

PGABOOST

Boost enable for input PGA:

0 = PGA output has +0dB gain

through input BOOST stage.

1 = PGA output has +20dB gain

through input BOOST stage.

Table 8 Input BOOST Stage Control

The auxilliary amplifier path to the BOOST stages is controlled by the AUXL2BOOSTVOL[2:0]

When AUXL2BOOSTVOL=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 L2 path to the BOOST stage is controlled by the LIP2BOOSTVOL[2:0] register bits.

When

L2_2BOOSTVOL=000 the L2 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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