TEA1099H View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TEA1099H

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

Loudspeaker amplifier: pins HFRX, GALS and LSAO

The TEA1099H has an asymmetrical input for the

loudspeaker amplifier with an input resistance of 20 kΩ

between pins HFRX and GND. It is biased at two diodes

voltage. Without limitation from the output, the input stage

can accommodate signals up to 580 mV (RMS) at room

temperature for 2% of THD.

The gain of the input stage varies according to the mode

of the TEA1099H. 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. The rail-to-rail output stage is

designed to power a loudspeaker connected as a

single-ended load (between pins LSAO and GND).

In the receive mode, the overall gain of the loudspeaker

amplifier can be adjusted from 0 up to 35 dB to suit specific

application requirements. The gain from HFRX to LSAO is

proportional to the value of RGALS and equals 28 dB with

RGALS = 255 kΩ. A capacitor connected in parallel with

RGALS is recommended and provides a 1st-order low-pass

filter.

Volume control: pin VOL

The loudspeaker amplifier gain can be adjusted with the

potentiometer RVOL. A linear potentiometer can be used to

obtain logarithmic control of the gain at the loudspeaker

amplifier. Each 1.9 kΩ 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.

Dynamic limiter: pin DLC

The dynamic limiter of the TEA1099H prevents clipping of

the loudspeaker output stage and protects the operation of

the circuit when the supply voltage at VBB falls below 2.7 V.

Hard clipping of the loudspeaker output stage is prevented

by rapidly reducing the gain when the output stage starts

to saturate. The time in which gain reduction is effected

(clipping attack time) is approximately a few milliseconds.

The circuit stays in the reduced gain mode until the peaks

of the loudspeaker signal no longer cause saturation.

The gain of the loudspeaker amplifier then returns to its

normal value within the clipping release time (typically

250 ms). Both attack and release times are proportional to

the value of the capacitor CDLC. The total harmonic

distortion of the loudspeaker output stage, in reduced gain

mode, stays below 2% up to 10 dB (minimum) of input

voltage overdrive [providing VHFRX is below

580 mV (RMS)].

When the supply voltage drops below an internal threshold

voltage of 2.7 V, the gain of the loudspeaker amplifier is

rapidly reduced (approximately 1 ms). When the supply

voltage exceeds 2.7 V, the gain of the loudspeaker

amplifier is increased again.

By forcing a level lower than 0.2 V on pin DLC, the

loudspeaker amplifier is muted and the TEA1099H is

automatically forced into the transmit mode.

RX amplifier using AUXO

In some cordless applications, the handset may be used to

perform handsfree function (instead of the base). As the

TEA1099H is in the base and the active loudspeaker is in

the handset, a second receive output is required.

The amplifier using HFRX as an input and AUXO as an

output will be used for communication with the RF IC,

sending information to the handset. It will be controlled by

the duplex controller in the same way as the loudspeaker

amplifier.

The voltage gain between pins HFRX and AUXO is equal

to 3.7 dB. The amplifier can manage the same input signal

as the loudspeaker amplifier. It has a rail-to-rail output,

biased by two diodes, designed for use with high ohmic

(real) loads (larger than 5 kΩ). The volume control and the

dynamic limiter are not active on this channel.

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.9.

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

amplified to TSEN. For the receive channel, the input

signal at HFRX 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 1st-order high-pass

filter. In the basic application (see Fig.16) it is assumed

that VTXIN = 1 mV (RMS) and VHFRX = 100 mV (RMS)

nominal and both RTSEN and RRSEN have a value of 10 kΩ.

With the value of CTSEN and CRSEN at 100 nF, the cut-off

frequency is at 160 Hz.

1999 Apr 08

14

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