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TEA1093 View Datasheet(PDF) - Philips Electronics

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Description
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TEA1093
Philips
Philips Electronics Philips
TEA1093 Datasheet PDF : 28 Pages
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Philips Semiconductors
Hands-free IC
Product specification
TEA1093
When the supply conditions drop below the required level,
the gain of the loudspeaker amplifier is reduced in order to
prevent the TEA1093 from malfunctioning. Only the gain of
the loudspeaker amplifier is affected since it is considered
to be the major power consuming part of the TEA1093.
When the TEA1093 experiences a loss of current, the
supply voltage VBB decreases. In this event, the gain of the
loudspeaker amplifiers is slowly reduced (approximately a
few seconds). When the supply voltage continues to
decrease and drops below an internal voltage threshold of
2.75 V, the gain of the loudspeaker amplifier is rapidly
reduced (approximately 1 ms). When normal supply
conditions are resumed, the gain of the loudspeaker
amplifier is increased again. This system ensures that in
the event of large continuous signals, all current is used to
power the loudspeaker while the voltage on pin VBB
remains at its nominal value.
By forcing a level lower than 0.2 V on pin DLC/MUTER, the
loudspeaker amplifier is muted and the TEA1093 is
automatically forced into the transmit mode.
Duplex controller
SIGNAL AND NOISE ENVELOPE DETECTORS: PINS TSEN,
TENV, TNOI, RSEN, RENV AND RNOI
The signal envelopes are used to monitor the signal level
strength in both channels. The noise envelopes are used to
monitor background noise in both channels. The signal and
noise envelopes provide inputs for the decision logic. The
signal and noise envelope detectors are shown in Fig.8.
For the transmit channel, the input signal at MIC is 40 dB,
amplified to TSEN. For the receive channel, the differential
signal between RIN1 and RIN2 is 0 dB amplified to RSEN.
The signals from TSEN and RSEN are logarithmically
compressed and buffered to TENV and RENV
respectively. The sensitivity of the envelope detectors is
set with RTSEN and RRSEN. 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.16, it is assumed that VMIC = 1 mV (RMS) and
VRIN = 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 capacitor 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 sufficient 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 sufficient for a smooth envelope and
also eliminates the effect of echoes on switching
behaviour.
handbook, full pagewidth
DUPLEX CONTROLLER
from
microphone
amplifier
LOG
to logic
from
loudspeaker
amplifier
LOG
to logic
1996 Feb 09
TSEN
28
(24)
TENV
27
(23)
RTSEN
TNOI
26
(22)
CTSEN
CTENV
CTNOI
RSEN
25
(21)
RENV
24
(20)
RRSEN
RNOI
23
(19)
CRSEN
CRENV
CRNOI
Fig.8 Signal and noise envelope detectors.
MGD223
10
 

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