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TEA1095 View Datasheet(PDF) - Philips Electronics

Part Name
Description
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TEA1095
Philips
Philips Electronics Philips
TEA1095 Datasheet PDF : 28 Pages
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Philips Semiconductors
Voice switched speakerphone IC
Product specification
TEA1095
The capacitors connected in series with the two resistors
block any DC component and form a first order high-pass
filter. In the basic application (see Fig.12), it is assumed
that VTXIN = 1 mV (RMS) and VRXIN = 100 mV (RMS)
nominal and both RTSEN and RRSEN have a value of 10 k.
With the value of CTSEN and CRSEN at 100 nF, the cut-off
frequency is at 160 Hz.
The buffer amplifiers leading the compressed signals to
TENV and RENV have a maximum source current of
120 µA and a maximum sink current of 1 µA. Together with
the capacitors CTENV and CRENV, the timing of the signal
envelope monitors can be set. In the basic application, the
value of both capacitors is 470 nF. Because of the
logarithmic compression, each 6 dB signal increase
means 18 mV increase of the voltage on the envelopes
TENV or RENV at room temperature. Thus, timings can be
expressed in dB/ms. At room temperature, the 120 µA
sourced current corresponds to a maximum rise-slope of
the signal envelope of 85 dB/ms. This is enough to track
normal speech signals. The 1 µA current sunk by TENV or
RENV corresponds to a maximum fall-slope of 0.7 dB/ms.
This is enough for a smooth envelope and also eliminates
the effect of echoes on switching behaviour.
To determine the noise level, the signal on TENV and
RENV are buffered to TNOI and RNOI. These buffers have
a maximum source current of 1 µA and a maximum sink
current of 120 µA. Together with the capacitors CTNOI and
CRNOI, the timing can be set. In the basic application of
Fig.12, the value of both capacitors is 4.7 µF. At room
temperature, the 1 µA sourced current corresponds to a
maximum rise-slope of the noise envelope of
approximately 0.07 dB/ms. This is small enough to track
background noise and not to be influenced by speech
bursts. The 120 µA current that is sunk corresponds to a
maximum fall-slope of approximately 8.5 dB/ms. However,
during the decrease of the signal envelope, the noise
envelope tracks the signal envelope so it will never fall
faster than approximately 0.7 dB/ms. The behaviour of the
signal envelope and noise envelope monitors is illustrated
in Fig.7.
handbook, full pagewidth
DUPLEX CONTROLLER
from
transmit
amplifier
LOG
to logic
from
receiver
amplifier
LOG
to logic
TSEN
TENV
TNOI
RTSEN
CTSEN
CTENV
CTNOI
RSEN
RENV
RNOI
RRSEN
CRSEN
CRENV
CRNOI
MBG355
1997 Nov 25
Fig.6 Signal and noise envelope detectors.
9
 

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