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TEA1099

Speech and handsfree IC with auxiliary inputs/outputs and analog multiplexer

Philips Electronics 

Philips Semiconductors

Speech and handsfree IC with auxiliary

inputs/outputs and analog multiplexer

Product specification

TEA1099H

EARPIECE AMPLIFIER (PINS GARX AND QR)

The earpiece amplifier is an operational amplifier having

its output (QR) and its inverting input (GARX) available.

Its input signal comes, via a decoupling capacitor, from the

receive RECO output. It is used in combination with two

resistors to get the required gain or attenuation compared

to the receive gain. It can be chosen between

−3 and +15 dB.

Two external capacitors CGAR (connected between GARX

and QR) and CGARS (connected between GARX and

GND) ensure stability. The CGAR capacitor provides a

1st-order low-pass filter. The cut-off frequency

corresponds to the time constant CGAR × Re2.

The relationship CGARS ≥ 10 × CGAR must be fulfilled.

The earpiece amplifier has a rail-to-rail output QR, biased

at two diodes voltage. It is designed for use with low ohmic

(real) loads (150 Ω) or capacitive loads (100 nF in series

with 100 Ω).

AUXILIARY RECEIVE AMPLIFIER (PINS RAUX AND RECO)

The auxiliary receive amplifier has an asymmetrical input

RAUX; it uses the RECO output. Its input impedance

between pins RAUX and GND is typically equal to 20 kΩ.

The voltage gain between pins RAUX and RECO is equal

to −2.4 dB. Without any limitation from the output, the input

stage can accommodate signals up to 0.95 V (RMS) at

room temperature for 2% of THD.

This auxiliary amplifier has a rail-to-rail output RECO,

which is designed for use with high ohmic (real) loads

(larger than 5 kΩ). This output is biased at two diodes

voltage.

The automatic gain control has no effect on this channel.

Auxiliary amplifiers using AUXO (pins MIC+, MIC−,

HFTX, IR and AUXO)

The TEA1099H has an auxiliary output AUXO, biased at

two diodes voltage. This output stage is a rail-to-rail one,

designed for use with high ohmic (real) loads (larger than

5 kΩ). The AUXO output amplifier is used in three different

channels, two transmit channels and one receive channel.

AUXILIARY AMPLIFIERS USING THE MICROPHONE INPUTS

(PINS MIC+, MIC− AND AUXO)

The auxiliary transmit amplifier using the microphone

MIC+ and MIC− inputs has a gain of 25.5 dB referenced to

AUXO. Without limitation from the output, the input stage

can accommodate signals up to 16 mV (RMS) at room

temperature for 2% of THD.

The automatic gain control has no effect on this channel.

AUXILIARY AMPLIFIERS USING HFTX

(PINS HFTX AND AUXO)

The auxiliary transmit amplifier using the HFTX input has

a gain of 15.2 dB referenced to AUXO.

The automatic gain control has no effect on this channel.

RX AMPLIFIER USING IR (PINS IR AND AUXO)

The auxiliary receive amplifier uses pin IR as input.

The input is referred to LN and the DC biasing between

these two pins is one diode voltage. The voltage gain

between the input IR (referenced to LN) and the output

AUXO is typically equal to 32.8 dB, which compensates

typically the attenuation provided by the anti-sidetone

network.

Automatic gain control is provided for line loss

compensation.

AGC (pin AGC)

The TEA1099H performs automatic line loss

compensation, which fits well with the true line attenuation.

The automatic gain control varies the gain of some

transmit and receive amplifiers in accordance with the DC

line current. The control range is 6.45 dB for Gv(MIC-LN),

Gv(IR-RECO) and Gv(IR-AUXO) and 6.8 dB for the other

affected channels, which corresponds approximately to a

line length of 5.5 km for a 0.5 mm twisted-pair copper

cable.

To enable this gain control, the AGC pin must be shorted

to pin LN. The start current for compensation corresponds

to a line current equal to typically 23 mA and the stop

current to 57 mA. The start current can be increased by

connecting an external resistor between pins AGC and LN.

It can be increased up to 40 mA (using a resistor typically

equal to 80 kΩ). The start and stop current will be

maintained in a ratio equal to 2.5. By leaving the AGC pin

open-circuit, the gain control is disabled and no line loss

compensation is performed.

1999 Apr 08

11

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