WM8608 datasheet(33/54 Pages) WOLFSON

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WM8608

PP Rev 1.5 March 2004

DIGITAL DEEMPHASIS

The digital ‘de-emphasis’ is used to equalize pre-emphasised digital CD recordings. De-emphasis

filtering is available on the Front-Left and Front-Right channels only, for sample rates of 32kHz,

44.1kHz and 48kHz. The settings are applied to the two channels simultaneously.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R20 (14h)

De-emphasis

DEEMP

De-emphasis Control

0 = No De-emphasis

1 = De-emphasis enabled

Table 31 De-emphasis

Refer to Figure 31, Figure 32, Figure 33, Figure 34, Figure 35 and Figure 36 for details of the De-

Emphasis modes at different sample rates.

Note: Using the De-emphasis filters for other sample rates as defined above will result in a frequency

response error as shown in Figure 32, Figure 34 and Figure 36.

DIGITAL VOLUME CONTROL

The volume control allows the gain of each channel to be independently adjusted in 0.5dB steps from

-103.5dB to +24dB. When the Dynamic Peak Compressor (see below) is enabled, gains of greater

than 0dB can be applied without digital clipping occurring. The volume control has a digital zero-cross

circuit which minimises clicks during changing the volume.

An update control bit is provided which allows the volume setting on each channel to be first stored in

an intermediate latch, then afterwards applied simultaneously to all channels. If UPDATE=0, the

Volume value will be written to the pre-latch but not applied to the relevant channel. If UPDATE=1, all

pre-latched values will be applied from the next input sample. The value of UPDATE itself is not

latched.

To prevent audible clicks, the volume control includes a ramp function which automatically ramps the

volume in small steps between register updates. The ramp rate is 256dB/s ±5%.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

7:0

VOLFL[7:0]

10110001

(-15dB)

Front-Left Volume in 0.5dB steps.

Refer to Table 14

R4 (04h)

Front-Left

Volume

UPDATE

Volume Update

0 = Store FLVOL in intermediate latch

(no gain change)

1 = Store and Update all channel

gains

7:0

VOLFR [7:0]

10110001

(-15dB)

Front-Right Volume in 0.5dB steps.

Refer to Table 14

R5 (05h)

Front-Right

Volume

UPDATE

Volume Update

0 = Store FRVOL in intermediate latch

(no gain change)

1 = Store and Update all channel

gains

7:0

VOLSL [7:0]

10110001

(-15dB)

Surround-Left Volume in 0.5dB steps.

Refer to Table 14

R6 (06h)

Surround-Left

Volume

UPDATE

Volume Update

0 = Store SLVOL in intermediate latch

(no gain change)

1 = Store and Update all channel

gains

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