WM8940CGEFLSLASHV datasheet(42/88 Pages) CIRRUS

42 / 88 page

WM8940

Rev 4.4

HI-FI DIGITAL TO ANALOGUE CONVERTER (DAC)

The DAC is enabled by the DACEN register bit.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

Power

Management 3

DACEN

DAC enable

0 = DAC disabled

1 = DAC enabled

Table 30 DAC Enable

The WM8940 also has a Soft Mute function, which gradually attenuates the volume of the digital

signal to zero. When removed, the gain will step back up to the digital gain setting. This function is

disabled by default. To play back an audio signal, it must first be disabled by setting the DACMU bit to

zero.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R10

DAC Control

DACMU

DAC soft mute enable

0 = DACMU disabled

1 = DACMU enabled

Table 31 DAC Control Register

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

interpolation filters. The bit stream 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.

AUTOMUTE

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

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

enabled using the AMUTE control bit.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R10

DAC Control

AMUTE

DAC auto mute enable

0 = auto mute disabled

1 = auto mute enabled

Table 32 DAC Auto Mute Control Register

DAC OUTPUT LIMITER

The WM8940 has a digital output limiter function. The operation of this is shown in Figure 20. 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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