WM8974 datasheet(28/63 Pages) WOLFSON

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WM8974

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PP Rev 1.1 September 2004

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

DACMU

DAC Softmute:

0 = Unmuted

1 = Muted

5:4

DEEMP

[1:0]

De-emphasis Control:

00 = No De-emphasis

01 = 32kHz sample rate

10 = 44.1kHz sample rate

11 = 48kHz sample rate

DACOSR

DAC oversampling rate:

0=64x (lowest power)

1=128x (best performance)

AMUTE

Automute enable

0 = Amute disabled

1 = Amute enabled

R10

DAC Control

DACPOL

DAC output polarity:

0 = non-inverted

1 = inverted (180 degrees phase shift)

Table 10 DAC Control Register

The digital audio data is converted to oversampled bit streams in the on-chip, true 24-bit digital

interpolation filters. The bitstream data enters a multi-bit, sigma-delta DAC, which converts it to a

high quality analogue audio signal. The multi-bit DAC architecture reduces high frequency noise and

sensitivity to clock jitter.

The DAC output defaults to non-inverted. Setting DACPOL will invert the DAC output phase on both

left and right channels.

AUTOMUTE

The DAC has an automute function which applied an analogue mute when 1024 consecutive zeros

are detected. The mute is release as soon as a non-zero sample is detected. Automute can be

disabled using the AMUTE control bit.

DAC OUTPUT LIMITER

The WM8974 has a digital output limiter function. The operation of this is shown in Figure 14. In

this diagram the upper graph shows the envelope of the input/output signals and the lower graph

shows the gain characteristic.

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