Philips CEM5000/00, Service Manual

Page: 42 / 83

11/30
TDA7419
5.3.4 Flat Mode
In flat mode the loudness stage works as a 0dB to -15dB attenuator.
5.4 SoftMute
The digitally controlled SoftMute stage allows muting/demuting the signal with a I
2
C-bus programmable
slope. The mute process can either be activated by the SoftMute pin or by the I
2
C-bus. This slope is real-
ized in a special S-shaped curve to mute slow in the critical regions (see Figure 8).
For timing purposes the Bit0 of the I2C-bus output register is set to 1 from the start of muting until the end
of demuting.
Figure 8. Sofmute Timing
Note: Please notice that a started Mute-action is always terminated and could not be interrupted by a change of the mute -signal
5.5 SoftStep-Volume
When the volume-level is changed audible clicks could appear at the output. The root cause of those clicks
could either be a DC-Offset before the volume-stage or the sudden change of the envelope of the audi-
osignal. With the SoftStep feature both kinds of clicks could be reduced to a minimum and are no more
audible. The blend-time from one step to the next is programmable in four steps.
Figure 9. SoftStep Timing
Note: For steps more than 0.5dB the SoftStep mode should be deactivated because it could generate a hard 1dB step during the blend-time.
1
EXT.
MUTE
+SIGNAL
REF
-SIGNAL
1
I
2
C BUS
OUT
Time
D97AU634
1dB
0.5dB
-0.5dB
-1dB
Time
D00AU1170
V
OUT
SS Time