Cirrus Logic CS4234 - Manual (Page 46)

DS899F1 46
CS4234
Table 8. Soft Ramp Rates
Full-scale ramp is 96 dB (-90 dB to +6 dB)
4.6.6.3 Noise Gate
The CS4234 is equipped with a Noise Gate feature that mutes the output of a given path if the signal drops
below a given bit depth for 8192 samples. This feature can be independently enabled for any of the three
output paths. While the enabling or disabling of the Noise Gate feature is done by output path, each of the
channels within the paths have separate monitoring circuitry that will trigger the Noise Gate function inde-
pendently of the other channels. For instance, if the Noise Gate were enabled for a given path and one of
the channels within that given path 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), indepen-
dently of the other channels within the same path. To enable the Noise Gate feature, set the xNG[2:0] bits
to the desired bit depth. The available bit depth settings are shown in
Table 9 .
When the upper “x” bits, as dictated by the xNG[2:0] settings, are either all “1’s” or all “0’s” for 8192 con-
secutive samples, the Noise Gate will engage for that channel. Setting all of these bits to ‘111’ will disable
the Noise Gate feature. If the Noise Gate feature engages for the Low-Latency path, the mute event will
occur immediately. If the Noise Gate feature engages for the DAC1-4 or DAC5 path, it will transition into
and out of mute as dictated by the
DAC1-4 ATT. and DAC5 ATT. bits in the "DAC Control 3" register .
Fs = 48 kHz or 96 kHz (Base = 48 kHz) Fs = 32 kHz or 64 kHz (Base = 32 kHz)
Ramp Rate
Time to Ramp
to Full Scale
(ms)
Time to Ramp
6 dB (ms)
ms/dB
Time to Ramp
to Full Scale
(ms)
Time to Ramp
6 dB (ms)
ms/dB
1 x Base 21.33 1.33 0.22 32 2 0.33
2 x Base 42.67 2.67 0.44 64 4 0.66
4 x Base 85.33 5.33 0.89 128 8 1.33
8 x Base 170.67 10.67 1.77 256 16 2.66
16 x Base 341.33 21.33 3.54 512 32 5.32
32 x Base 682.67 42.67 7.09 1024 64 10.63
64 x Base 1365.33 85.33 14.17 2048 128 21.26
128 x Base 2730.67 170.67 28.35 4096 256 42.52
xNG[2:0] Setting Channel is muted after “x” bits
000 Upper 13 Bits (-72 dB)
001 Upper 14 Bits (-78 dB)
010 Upper 15 Bits (-82 dB)
011 Upper 16 Bits (-90 dB)
100 Upper 17 Bits (-94 dB)
101 Upper 18 Bits (-102 dB)
110 Upper 24 Bits (-138 dB)
111 Noise Gate Disabled
Table 9. Noise Gate Bit Depth Settings