tea1099h NXP Semiconductors, tea1099h Datasheet - Page 14

• Manufacturer Part Number: tea1099h
• Description: Speech And Handsfree Ic With Auxiliary Inputs/outputs And Analog Multiplexer
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Loudspeaker amplifier: pins HFRX, GALS and LSAO
The TEA1099H has an asymmetrical input for the
loudspeaker amplifier with an input resistance of 20 k
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 R
R
R
filter.
Volume control: pin VOL
The loudspeaker amplifier gain can be adjusted with the
potentiometer R
obtain logarithmic control of the gain at the loudspeaker
amplifier. Each 1.9 k increase of R
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 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 C
distortion of the loudspeaker output stage, in reduced gain
mode, stays below 2% up to 10 dB (minimum) of input
voltage overdrive [providing V
580 mV (RMS)].
1999 Apr 08
GALS
GALS
Speech and handsfree IC with auxiliary
inputs/outputs and analog multiplexer
is recommended and provides a 1st-order low-pass
= 255 k . A capacitor connected in parallel with
VOL
. A linear potentiometer can be used to
DLC
GALS
HFRX
. The total harmonic
and equals 28 dB with
is below
VOL
BB
results in a gain
falls below 2.7 V.
14
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 k ). The volume control and the
dynamic limiter are not active on this channel.
D
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 R
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 V
nominal and both R
With the value of C
frequency is at 160 Hz.
UPLEX CONTROLLER
TXIN
= 1 mV (RMS) and V
TSEN
TSEN
and R
and C
RSEN
RSEN
HFRX
have a value of 10 k .
at 100 nF, the cut-off
Product specification
= 100 mV (RMS)
TSEN
TEA1099H
and R
RSEN
.