WM8978GEFLSLASHV datasheet(33/78 Pages) WOLFSON

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WM8978

PP Rev 1.7 January 2005

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

left channel and DACPOLR inverts the phase on the right channel.

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

disabled using the AMUTE control bit.

DIGITAL HI-FI DAC VOLUME (GAIN) CONTROL

The signal volume from each Hi-Fi DAC can be controlled digitally. The gain and attenuation range

is –127dB to 0dB in 0.5dB steps. The level of attenuation for an eight-bit code X is given by:

0.5

× (X-255) dB for 1 ≤ X ≤ 255;

MUTE for X = 0

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

7:0

DACVOLL

[7:0]

11111111

( 0dB )

Left DAC Digital Volume Control

0000 0000 = Digital Mute

0000 0001 = -127dB

0000 0010 = -126.5dB

... 0.5dB steps up to

1111 1111 = 0dB

R11

Left DAC

Digital Volume

DACVU

Not

latched

DAC left and DAC right volume do

not update until a 1 is written to

DACVU (in reg 11 or 12)

7:0

DACVOLR

[7:0]

11111111

( 0dB )

Right DAC Digital Volume Control

0000 0000 = Digital Mute

0000 0001 = -127dB

0000 0010 = -126.5dB

... 0.5dB steps up to

1111 1111 = 0dB

R12

Right DAC

Digital Volume

DACVU

Not

latched

DAC left and DAC right volume do

not update until a 1 is written to

DACVU (in reg 11 or 12)

Table 20 DAC Digital Volume Control

Note: An additional gain of up to +12dB can be added using the gain block embedded in the

digital peak limiter circuit (see DAC OUTPUT LIMITER section).

DAC 5-BAND EQUALISER

A 5-band graphic equaliser function which can be used to change the output frequency levels to suit

the environment. This can be applied to the ADC or DAC path and is described in the 5-BAND

EQUALISER section for further details on this feature.

DAC 3-D ENHANCEMENT

The WM8978 has an advanced digital 3-D enhancement feature which can be used to vary the

perceived stereo separation of the left and right channels. Like the 5-band equaliser this feature can

be applied to either the record path or the plaback path but not both simultaneously. See the 3-D

STEREO ENHANCEMENT section for further details on this feature.

DAC DIGITAL OUTPUT LIMITER

The WM8978 has a digital output limiter function. The operation of this is shown in Figure 13. 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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