CDB6420 Cirrus Logic Inc, CDB6420 Datasheet - Page 17
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CDB6420
Manufacturer Part Number
CDB6420
Description
Development Kit
Manufacturer
Cirrus Logic Inc
Datasheet
1.CDB6420.pdf
(52 pages)
Specifications of CDB6420
Silicon Manufacturer
Cirrus Logic
Application Sub Type
Speakerphone
Kit Application Type
Audio / Video / TV
Silicon Core Number
CS6420
Kit Contents
Board
Kit Features
Analog And Digital Patch Area
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
RHDet - Receive Half-Duplex Detection
Threshold
The sensitivity of the speech detector controls
channel switching and ownership in half-duplex
mode. The receive speech detector registers speech
if the receive channel signal power is RHDet above
the noise floor for the receive channel.
HDly - Half-Duplex Holdover Delay
After a channel goes idle in the half-duplex mode
of operation, a change of channel ownership is in-
hibited for HDly in order to prevent false switching
due to echoes. The half-duplex will be more im-
mune to false switching if this delay is longer, but
it will also prevent a fast response to legitimate
channel changes.
NseRmp - Background Noise Power Estimator
Ramp Rate
The background noise power estimators increase at
a rate of 3 dB/NseRmp until the background noise
power estimate equals the current input power esti-
mate. The background noise power estimators
quickly track drops in the current input power esti-
mate. Choose small values of NseRmp if the envi-
ronment is expected to have rapidly varying noise
levels. Choose large values of NseRmp if the envi-
ronment is expected to have relatively constant
noise power.
DS205PP2
RSThd - Receive Suppression Threshold
This parameter sets the threshold for far-end
speech detection for disengaging receive suppres-
sion. The speech detector that disengages the re-
ceive suppression has its sensitivity controlled by
RSThd. The suppression is inserted into the receive
path unless signal from the far-end exceeds the re-
ceive channel noise power by RSThd, in which
case speech is assumed to be detected and the sup-
pression is defeated until speech is no longer de-
tected. Decreasing RSThd to make the speech
detector more sensitive could result in false detec-
tions due to spurious noise events which may cause
an unpleasant noise modulation at the near-end. In-
creasing RSThd to make it robust to spurious noise,
but may cause weak far-end talkers to not be heard.
RSThd does not affect the ability of the receive
suppressor to attenuate residual network echo.
PCSen- Path Change Sensitivity
The Acoustic Interface is likely to have many path
changes, for example, as people move about in the
room where the full-duplex speakerphone is being
used. The sensitivity of the path change detector
can be changed with the PCSen Bit. Set PCSen to 0
for high sensitivity and 1 for low sensitivity.
If PCSen is set to high, extended doubletalk may
cause the CS6420 to briefly drop into half-duplex.
When PCSen is set to low, brief echo may be heard
during path changes.
CS6420
17