WM8974 datasheet(34/63 Pages) WOLFSON

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WM8974

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PP Rev 1.1 September 2004

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

SPKBOOST

Speaker output boost stage control (see

Table 20 for details)

0=No boost (outputs are inverting buffers)

1 = 1.5x gain boost

R49

Output control

MONOBOOST

Mono output boost stage control (see

Table 20 for details)

0=No boost (output is inverting buffer)

1=1.5x gain boost

Power

management 1

BUFDCOPEN

Dedicated buffer for DC level shifting

output stages when in 1.5x gain boost

configuration.

0=Buffer disabled

1=Buffer enabled (required for 1.5x gain

boost)

Table 19 Output Boost Control

SPKBOOST/

MONOBOOST

OUTPUT

STAGE GAIN

OUTPUT DC

LEVEL

OUTPUT STAGE

CONFIGURATION

AVDD/2

Inverting

1.5x

1.5xAVDD/2

Non-inverting

Table 20 Output Boost Stage Details

SPKROUTP/SPKROUTN OUTPUTS

The SPKROUT pins can drive a single bridge tied 8Ω speaker or two headphone loads of 16

Ω or

Ω or a line output (see Headphone Output and Line Output sections, respectively). The signal to

be output on SKPKOUT comes from the Speaker Mixer circuit and can be any combination of the

DAC output, the Bypass path (output of the boost stage) and the AUX input. The SPKROUTP/N

volume is controlled by the SPKRVOL register bits. Note that gains over 0dB may cause clipping if

the signal is large. The SPKMUTE register bit causes the speaker outputs to be muted (the output

DC level is driven out). The output pins remains at the same DC level (VMIDOP), so that no click

noise is produced when muting or un-muting.

The SPKROUTN pin always drives out an inverted version of the SPKROUTP signal.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

DAC2SPK

Output of DAC to speaker mixer input

0 = not selected

1 = selected

BYP2SPK

Bypass path (output of input boost

stage) to speaker mixer input

0 = not selected

1 = selected

R50

Speaker mixer

control

AUX2SPK

Output of auxiliary amplifier to speaker

mixer input

0 = not selected

1 = selected

Table 21 Speaker Mixer Control

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