CS4244-CNZ Cirrus Logic Inc, CS4244-CNZ Datasheet - Page 40

• Manufacturer Part Number: CS4244-CNZ
• Description: IC 4 Input / 5 Output CODEC
• Manufacturer: Cirrus Logic Inc

DS900PP2
resulting in audible zipper noise if the ramp rate is set too high. By instead adapting the soft-ramp rate to
fit the envelope given by the incoming volume samples, the envelope lag time is limited and the zipper
noise is avoided. In this mode the soft ramp algorithm linearly interpolates the volume between the volume
changes. There is a lag of one volume change sample since two samples are required to calculate the
first ramp rate.
See
the possible beginning of a volume envelope sequence and resets an envelope counter. The volume
starts ramping to the new volume setting at a constant rate controlled by the
If the envelope counter times out before a new volume sample is received, the next received sample is
treated in the same way as the previous sample and the ramp rate is kept constant. In this way, as long
as the volume samples are distant from each other by more than the envelope counter time out, the rate
is kept constant resulting in the soft-ramp behavior described in the button-press example.
However if the next volume sample is received before the envelope counter times out, then it is assumed
to be part of a volume envelope sequence. The envelope counter is reset and as long as new samples
are received in succession before a time out occurs, the sequence is continued. Starting at the second
volume sample of an envelope sequence, the ramp rate is adjusted using the equation shown in
Figure
Two control parameters allow the user to limit the ramp-rate range to achieve optimum effect. The
DELAY[2:0]
tracking while providing a smoother ramp. The
Figure 30
30.
setting limits the maximum ramp rate; higher values will introduce more lag in the envelope
for the soft ramp diagram. On the first volume sample received, the CS4244 only detects
Ramp
Rate
Figure 30. Soft Ramp Behavior

New
Volume
Envelope Counter
Limit Ramp Rate
Volume or Mute
Reset Envelope
Time
USER: Change
Timed Out?
Wait State
Envelope
Running
Register
Counter
Counter
Between
Setting
No
MAX DELAY[2:0]
-
Volume
Current
Yes
Changes
Volume
MAX_DELAY
MIN_DELAY
Setting
Reset Envelope
MUTE_DELAY
Ramp Rate =
Counter
setting limits the minimum ramp rate;
MUTE DELAY[1:0]
CS4244
setting.
MIN
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