PSB2163T-V31TR Infineon Technologies, PSB2163T-V31TR Datasheet - Page 142

• Manufacturer Part Number: PSB2163T-V31TR
• Description: IC AUDIO RINGING CODEC 28-PDSO
• Manufacturer: Infineon Technologies
• Series: ARCOFI®r

Specifications of PSB2163T-V31TR

• Function: CODEC Filter
• Interface: IOM-2, PCI, Serial
• Number Of Circuits: 1
• Voltage - Supply: 5V
• Current - Supply: 900µA
• Power (watts): 1mW
• Operating Temperature: -25°C ~ 80°C
• Mounting Type: Surface Mount
• Package / Case: DSO-28
• Includes: Activation and Deactivation, B-Channel and D-Channel HDLC Controllers, D-Channel Priority Handler, Monitor Channel Handler
• Lead Free Status / RoHS Status: Request inventory verification / Request inventory verification
• Other names: PSB2163T-V31INTR; PSB2163T-V31TR

Speakerphone Implementation
The speech detectors are able to distinguish between speech signals and any kind of
noise and inform the attenuation control unit about the presence or absence of speech
in the receive and the transmit path.
Assume the speakerphone is in receive mode, therefore outgoing digital signals are
attenuated in the GHX stage, incoming signals from the PCM interface are reproduced
by the loudspeaker with no attenuation inserted in the GHR stage. Of course the speech
detector in receive direction has recognized speech - otherwise the receive mode would
not be active. At the output of the microphone amplifier there is a signal mixture
consisting of coupled sound coming from the loudspeaker and from reflections in the
room. But also speech activity taking place at the near end in front of the speakerphone
will appear in the transmit path (which is still attenuated, if the ARCOFI-SP is in receive
mode). The task of the attenuation control unit is now to distinguish between unwanted
signals resulting from coupling, echoes etc. and true speech activity. True speech
activity has to make the ARCOFI-SP switch into transmit mode. For this purpose, first of
all the speech detector in transmit direction must have recognized any speech activity.
When both speech detectors have recognized speech activity, a decision must be made,
which mode is to use (receive or transmit). This is done by the speech comparators, in
this example by the speech comparator for the acoustic echo, SCAE. The speech
comparator for the acoustic echo "knows" exactly what signal level SX must be regarded
as an echo and which signal level is higher than an echo ever can be. If such a high
signal level appears, and this level is a certain (programmable) amount higher than the
signal level SR that is actually being received, the speech comparator will change state,
therefore indicating this fact to the attenuation control unit. As a result, mode switching
from receive mode to transmit mode will happen.
The same explanation applies to the mode switching from transmit mode to receive
mode, but in this case not the acoustic echo must be taken into account, but the line echo
resulting from delays and reflections in the telephone network is important. This echo is
handled by the speech comparator for the line echo, SCLE.
A mode switching can be forced simply by speaking louder than the remote partner. How
many "dBs" louder a person has to speak is programmable, but always the speech
comparators have to cover the worst case echo. That means for the application, that a
speakerphone system with a high acoustical coupling and with strong resonances will
show a reduced speakerphone performance, since for winning the channel one always
has to be louder than the signal caused by echoes and couplings. But for an appropriate
designed telephone plastics (refer to chapter 1.6), a very comfortable behavior regarding
mode switching is achieved.
If no speech activity is recognized by the ARCOFI-SP, the speakerphone goes into idle
mode. After both speech detectors have indicated "no speech", the ARCOFI-SP remains
in the previous mode for the period of time programmed by TW. After TW has passed,
the quantity of switchable attenuation (in dB) is changed to the amount of half the value
determined by ATT in both branches (see table below) with the speed given by DS
Semiconductor Group
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