User Manual

DS680F2 27
CS42L52
3/1/13
4.2.3 Noise Gate
The noise gate may be used to mute signal levels that fall below a programmable threshold. This prevents
the ALC from applying gain to noise. A programmable delay may be used to set the minimum time before
the noise gate attacks the signal.
Note: Maximum noise gate attenuation levels will depend on the gain applied in either the PGA or MIC
pre-amplifier. For example: If both +32 dB pre-amplification and +12 dB programmable gain is applied,
the maximum attenuation that the noise gate achieves will be 52 dB (-96 + 32 + 12) below full-scale.
Referenced Control Register Location
PGAxVOL[5:0
MAX[2:0], MIN[2:0]
“PGAx Vol. and ALCx Transition Ctl.: ALC, PGA A (Address 12h) and ALC, PGA B (Address 13h)” on
page 55
“ALC Threshold (Address 2Ch)” on page 68
Referenced Control Register Location
Noise Gate Controls............ “Noise Gate Control (Address 2Dh)” on page 69
Output
(after ALC)
Input (before ALC)
RRATE[5:0]
PGA Gain and/or
Attenuator
ALC
Response
MAX[2:0]
ARATE[5:0
]
below full scale
MIN[2:0]
below full scale
MIN[2:0]
below full scale
MAX[2:0]
below full scale
Figure 8. ALC
-96 -40
THRESH[2:0]
Maximum Attenuation*
-52 dB
Output
(dB)
Input (dB)
N
G
E
N
=
1
N
G
E
N
=
0
-80 dB
-64 dB
Figure 9. Noise Gate Attenuation