PSB21473FV13XT Infineon Technologies, PSB21473FV13XT Datasheet - Page 392

• Manufacturer Part Number: PSB21473FV13XT
• Manufacturer: Infineon Technologies

Specifications of PSB21473FV13XT

• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (min): 3.135V
• Operating Supply Voltage (max): 3.6V
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 144
• Lead Free Status / RoHS Status: Compliant

Data Sheet
Figure 20-16 Echo Suppression Unit - Automatic Gain Control
For reasons of physiological acceptance, the AGC gain is automatically reduced in case
of continuous background noise (e.g. by ventilators). The reduction is programmed via
the NOlS parameter. When the noise level exceeds the threshold determined by NOIS,
the amplification will be reduced by the same amount the noise level is above the
threshold.
The regulation speed is controlled by SPEEDH for signal amplitudes above the threshold
and SPEEDL for amplitudes below. Usually SPEEDH will be chosen to be at least 10
times faster than SPEEDL. An additional low pass with time constant LP is provided to
avoid an immediate response of the AGC to very short signal bursts. The time constant
of the low pass should not be selected longer than 4 ms in order to avoid unstable
behavior.
If the speech detector SDX detects noise or the receive path is active, AGCX freezes its
current attenuation and the last gain setting is used. Regulation starts with this value as
soon as SDX detects speech and the receive path is inactive. Likewise, if SDR detects
noise or the transmit path is active, AGCR freezes its current attenuation and the last
gain setting is used. Regulation starts with this value as soon as SDR detects speech
and the transmit path is inactive.
The current gain/attenuation of the AGC can be read at any time (AG_CUR). When the
AGC has been disabled, the initial gain used immediately after enabling the AGC can be
programmed. Table 20-13 shows the parameters of the AGC.
AG_GAIN
AG_ATT
Example:
COM
=
=
=
-30 dB
15 dB
20 dB
AG_GAIN
AGC input level
392
-20 dB
-10 dB
AG_ATT
Digital Signal Processor
max. PCM
COM
-10 dB
-20 dB
AGC
output
level
PSB 21473
2003-03-31
INCA-D