psb21391 Infineon Technologies Corporation, psb21391 Datasheet - Page 133

• Manufacturer Part Number: psb21391
• Description: Siemens Codec With Upn Transceiver
• Manufacturer: Infineon Technologies Corporation

Figure 67
Speakerphone Signal Flow Graph of the SCOUT-PX
4.4.1
The Attenuation Control unit controls the attenuation stages GHX of the transmit and
GHR of the receive directions respectively. The programmable loss is switched either
completely to a single path or, in the “IDLE” mode, is halved to each direction.
In addition, attenuation is also influenced by the Automatic Gain Control stages (AGCX
and AGCR). In order to keep the total loop gain always constant, the sweep range (of
ATT) is automatically enlarged with high-gain amplification of the AGCs while it will be
accordingly reduced with low-gain.
Changing from one speakerphone mode into another one depends on the
determinations of one comparator plus the corresponding speech detector. Hence
attenuation is influenced by the current and past speech activities. Also rate of change
varies: changing from “transmit mode” or “receive mode” to “idle mode” is programmable
by the rate factor DS. Direct changes from “transmit mode” to “receive mode” or vice-
versa and changes from “idle mode” to “transmit mode” or “receive mode” can be
programmed via the factor SW in a large range.
Data Sheet
Signal-Processing
Analog Front End
Signal-Processing
Analog Front End
Attenuation Control Unit
&
&
SX
SR
SCAE
SD
AGCX
Attenuation
GR
Control
123
GHX
GHR
SD
AGCR
SCLE
SR´
SX´
PSB 21391
PSB 21393
COMP
EXP
2001-03-07
Codec
PCM
PCM