CS4244 Datasheet, PDF (41/63 Pages) Cirrus Logic – 4 In/4 Out Audio CODEC with PCM and TDM Interfaces

CS4244
tracking and always produce a constant ramp rate. To accomplish this, set the MIN DELAY[2:0] and MAX
DELAY[2:0] values to match the MUTE DELAY[1:0] setting.
The envelope counter time out period which defines the boundary between the two soft-ramping behav-
iors depends on the base rate. It is equal to approximately 100,000/Fs.
The MUTE DELAY[1:0], MIN DELAY[2:0], and MAX DELAY[2:0] bits specify a delay equal to a multiple
of the base period between volume steps of ^6.02/₆₄ dB, which is approximately 0.1 dB. This is the internal
resolution of the volume control engine. Consequently the soft-ramp rate can be expressed in ms/dB as
shown in Table 6.
Ramp Rate
1 x Base
2 x Base
4 x Base
8 x Base
16 x Base
32 x Base
64 x Base
128 x Base
Fs = 48 kHz or 96 kHz (Base = 48 kHz)
Time to Ramp
to Full Scale
(ms)
Time to Ramp
6 dB (ms)
ms/dB
21.33
1.33
0.22
42.67
2.67
0.44
85.33
5.33
0.89
170.67
10.67
1.77
341.33
21.33
3.54
682.67
42.67
7.09
1365.33
85.33
14.17
2730.67
170.67
28.35
Fs = 32 kHz or 64 kHz (Base = 32 kHz)
Time to Ramp
to Full Scale
(ms)
Time to Ramp
6 dB (ms)
ms/dB
32
2
0.33
64
4
0.66
128
8
1.33
256
16
2.66
512
32
5.32
1024
64
10.63
2048
128
21.26
4096
256
42.52
Table 6. Soft Ramp Rates
Full-scale ramp is 96 dB (-90 dB to +6 dB)
4.6.5.3 Noise Gate
The CS4244 is equipped with a Noise Gate feature that mutes the output if the signal drops below a given
bit depth for 8192 samples. While the enabling or disabling of the Noise Gate feature is done for the entire
DAC1-4 output path, each of the channels within the path have separate monitoring circuitry that will trig-
ger the Noise Gate function independently of the other channels. For instance, if the Noise Gate were en-
abled for and one of the channels were to exhibit a pattern of more than 8192 samples of either all “1’s”
or all “0’s”, the output for that particular channel would be muted (and subsequently unmuted), inde-
pendently of the other channels. To enable the Noise Gate feature, set the DAC1-4 NG[2:0] bits to the
desired bit depth. The available bit depth settings are shown in Table 7.
DS900F2
DAC1-4 NG[2:0] Setting
000
001
010
011
100
101
110
111
Channel is muted after “x” bits
Upper 13 Bits (-72 dB)
Upper 14 Bits (-78 dB)
Upper 15 Bits (-82 dB)
Upper 16 Bits (-90 dB)
Upper 17 Bits (-94 dB)
Upper 18 Bits (-102 dB)
Upper 24 Bits (-138 dB)
Noise Gate Disabled
Table 7. Noise Gate Bit Depth Settings
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