WM8976 datasheet(48/108 Pages) WOLFSON

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WM8976

Pre-Production

PP Rev 3.0 April 2006

3D STEREO ENHANCEMENT

The WM8976 has a digital 3D enhancement option to increase the perceived separation between the

left and right channels. Selection of 3D for playback is controlled by register bit EQ3DMODE.

Switching this bit from record to playback or from playback to record may only be done when ADC

and DAC are disabled. The WM8976 control interface will only allow EQ3DMODE to be changed

when ADC and DAC are disabled (ie ADCENL = 0, ADCENR = 0, DACENL = 0 and DACENR = 0).

The DEPTH3D setting controls the degree of stereo expansion.

When 3D enhancement is used, it may be necessary to attenuate the signal by 6dB to avoid limiting.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R41 (29h)

3:0

DEPTH3D[3:0]

0000

Stereo depth

0000: 0% (minimum 3D effect)

0001: 6.67%

....

1110: 93.3%

1111: 100% (maximum 3D effect)

Table 37 3D Stereo Enhancement Function

ANALOGUE OUTPUTS

The WM8976 has three sets of stereo analogue outputs. These are:

•

LOUT1 and ROUT1 which are normally used to drive a headphone load.

•

LOUT2 and ROUT2 – normally used to drive an 8Ω BTL speaker.

•

OUT3 and OUT4 – can be configured as a stereo line out (OUT3 is left output and

OUT4 is right output). OUT4 can also be used to provide a mono mix of left and right

channels.

LOUT2, ROUT2, OUT3 and OUT4 are supplied from SPKVDD and are capable of driving up to

1.5Vrms signals as shown in Figure 20. LOUT1 and ROUT1 are supplied from AVDD and can only

drive out a 1V rms signal (AVDD/3.3).

LOUT1, ROUT1, LOUT2 and ROUT2 have individual analogue volume PGAs with -57dB to +6dB

ranges.

There are four output mixers in the output signal path, the left and right channel mixers which control

the signals to speaker, headphone (and optionally the line outputs) and also dedicated OUT3 and

OUT4 mixers.

LEFT AND RIGHT OUTPUT CHANNEL MIXERS

The left and right output channel mixers are shown in Figure 20.

These mixers allow the AUX

inputs, the ADC bypass and the DAC left and right channels to be combined as desired.

This

allows a mono mix of the DAC channels to be done as well as mixing in external line-in from the

AUX or speech from the input bypass path.

The AUX and bypass inputs have individual volume control from -15dB to +6dB and the DAC volume

can be adjusted in the digital domain if required. The output of these mixers is connected to both

the headphone (LOUT1 and ROUT1) and speaker (LOUT2 and ROUT2) and can optionally be

connected to the OUT3 and OUT4 mixers.

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