TEA1095T View Datasheet(PDF) - Philips Electronics

Part Name

Description

View to exact match

TEA1095T

Voice switched speakerphone IC

Philips Electronics 

Philips Semiconductors

Voice switched speakerphone IC

Receive channel

Product specification

TEA1095

handbook, full pagewidth

to loudspeaker

amplifier

RGARX

CGARX

GARX

RXOUT

VI

MUTERX

to

to/from envelope

voice switch detector

IV

RXIN

from transmission

circuit

VOLUME

CONTROL

VOL

RVOL

MBG356

Fig.5 Receive channel.

RECEIVER AMPLIFIER: PINS RXIN, GARX, RXOUT AND

MUTERX

The TEA1095 has an asymmetrical input (RXIN) for the

receiver amplifier with an input resistance of 20 kΩ. The

gain of the input stage varies according to the mode of the

TEA1095. In the receive mode, the gain is at its maximum;

in the transmit mode, it is at its minimum and in the idle

mode, it is halfway between maximum and minimum.

Switch-over from one mode to the other is smooth and

click-free.

In the receive mode, the overall gain of the receive

amplifier can be adjusted from −14 dB to +26 dB to suit

application specific requirements. The gain from RXIN to

RXOUT is proportional to the value of RGARX and equals

6.5 dB with RGARX = 16.5 kΩ. A capacitor connected in

parallel with RGARX can be used to provide a first-order

low-pass filter.

By applying a HIGH level on pin MUTERX, the receiver

amplifier is muted and the TEA1095 is automatically

forced into the transmit mode.

VOLUME CONTROL: PIN VOL

The receiver amplifier gain can be adjusted with the

potentiometer RVOL. A linear potentiometer can be used to

obtain logarithmic control of the gain of the receiver

amplifier. Each 950 Ω increase of RVOL results in a gain

loss of 3 dB. The maximum gain reduction with the volume

control is internally limited to the switching range.

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 envelopes detectors are shown in

Fig.6.

For the transmit channel, the input signal at TXIN is 40 dB

amplified to TSEN. For the receive channel, the input

signal at RXIN 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.

1997 Nov 25

8

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