WM8608 ETC-unknow, WM8608 Datasheet - Page 33

• Manufacturer Part Number: WM8608
• Description: The Wm8608 Comprises A High Performance Multi-channel Pwm Digital Power Amplifier Controller. Simply By Adding Appropriate Power Output Stages A Multi-channel Power Amplifier May Be Built. Six Identical Full Audio Bandwidth Channels, Plus A Reduced B
• Manufacturer: ETC-unknow

Product Preview
DIGITAL DEEMPHASIS
DIGITAL VOLUME CONTROL
w
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.
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.
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%.
R20 (14h)
De-emphasis
R4 (04h)
Front-Left
Volume
R5 (05h)
Front-Right
Volume
R6 (06h)
Surround-Left
Volume
REGISTER
ADDRESS
REGISTER
ADDRESS
8
8
8
7:0
7:0
7:0
BIT
BIT
0
VOLFL[7:0]
UPDATE
VOLFR [7:0]
UPDATE
VOLSL [7:0]
UPDATE
DEEMP
LABEL
LABEL
DEFAULT
10110001
(-15dB)
0
10110001
(-15dB)
0
10110001
(-15dB)
0
DEFAULT
0
0 = No De-emphasis
1 = De-emphasis enabled
Front-Left Volume in 0.5dB steps.
Refer to Table 14
0 = Store FLVOL in intermediate latch
1 = Store and Update all channel
Front-Right Volume in 0.5dB steps.
Refer to Table 14
0 = Store FRVOL in intermediate latch
1 = Store and Update all channel
Surround-Left Volume in 0.5dB steps.
Refer to Table 14
0 = Store SLVOL in intermediate latch
1 = Store and Update all channel
gains
De-emphasis Control
Volume Update
Volume Update
Volume Update
(no gain change)
gains
(no gain change)
gains
(no gain change)
DESCRIPTION
DESCRIPTION
PP Rev 1.5 March 2004
WM8608
33