WM8608 datasheet(41/54 Pages) WOLFSON

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WM8608

PP Rev 1.5 March 2004

ZERO-CROSS DETECT

The Dynamic Peak Compressor has a zero-cross detect that minimises clicks during gain changes.

The zero-cross detect can be enabled/disabled in channel-pairs. The zero-cross has a timeout

feature which ensures that the volume will change even if the input has a large DC offset. Once a

new gain has been requested from the Dynamic Peak Compressor, the zero-cross detector will wait

for a zero-cross for 25 to 50 ms before applying the gain change.

Note that the zero-cross settings programmed here also apply to the Dynamic Peak Compressor.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

ZCF

Zero-Cross Enable – Front Channels:

0 : Disable Zero-Cross

Enable Zero-Cross

ZCS

Zero-Cross Enable – Surround

Channels:

0 : Disable Zero-Cross

Enable Zero-Cross

ZCC

Zero-Cross Enable – Front Centre and

Rear Centre Channels:

0 : Disable Zero-Cross

Enable Zero-Cross

ZCSUB

Zero-Cross Enable – Sub Channel:

0 : Disable Zero-Cross

Enable Zero-Cross

R25 (19h)

Volume

Control Zero-

Cross

ZCT

Zero Cross Timeout Enable:

0 : Disable Zero-Cross Timeout

Enable Zero-Cross Timeout

Table 40 Volume Control Zero-Cross

INTERPOLATION FILTERS

The WM8608 uses two types of interpolation filters, selected according to sampling frequency, as

shown in Table 40.

SAMPLING FREQUENCY

FILTER TYPE

INTERPOLATION

Main Channels

SUB

32kHz

12x

44.1kHz

48kHz

88.2kHz

96kHz

176.4kHz

192kHz

Table 41 Interpolation Filter Types

Note: If the Subwoofer channel is redirected into the Rear Centre (RC) channel the main channel

characteristics apply.

FILTER TYPE 0

PARAMETER

SYMBOL

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Filter

Passband

±0.05 dB

0.454

Stopband

-3dB

0.484

Passband ripple

±0.05

Stopband Attenuation

f > 0.546fs

-60

Group Delay

samples

Table 42 Digital Filter 0 Characteristics

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