tea1097h NXP Semiconductors, tea1097h Datasheet - Page 12

• Manufacturer Part Number: tea1097h
• Description: Speech And Loudspeaker Amplifier Ic With Auxiliary Inputs/outputs And Analog Multiplexer
• Manufacturer: NXP Semiconductors

Philips Semiconductors
E
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 C
GARX and QR) and C
GARX and GND) ensure stability. The C
provides a first-order low-pass filter. The cut-off frequency
corresponds to the time constant C
The relationship C
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 ) or capacitive loads (100 nF in series
with 100 ).
When the amplifier is turned off, the signal present on the
earpiece is equal to the ratio between the load on QR and
R
A
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 k .
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 k ). 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 TEA1097 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 k ). The AUXO output amplifier is used in three different
channels, two transmit channels and one receive channel.
1999 Apr 08
ARPIECE AMPLIFIER
UXILIARY RECEIVE AMPLIFIER
e1
Speech and loudspeaker amplifier IC with
auxiliary inputs/outputs and analog multiplexer
+ R
e2
GARS
(
PINS
GARS
10
GARX
GAR
(connected between pins
(
PINS
(connected between pins
C
GAR
AND
RAUX
GAR
must be fulfilled.
QR)
GAR
R
AND
e2
capacitor
.
RECO)
12
A
(
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.
A
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
The auxiliary receive amplifier uses pin IR as input.
The input is referenced to pin 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.
Automatic gain control (pin AGC)
The TEA1097 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 G
G
approximately to a line length of 5.5 km for a 0.5 mm
twisted-pair copper cable.
To enable this gain control, the pin AGC 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 to 40 mA (using a resistor typically
equal to 80 k ). 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.
PINS
UXILIARY AMPLIFIERS USING THE MICROPHONE INPUTS
UXILIARY AMPLIFIERS USING
v(IR-AUXO)
AMPLIFIER USING
MIC+, MIC
and 6.8 dB for G
AND
IR (
AUXO)
PINS
v(TXAUX-LN)
HFTX (
IR
AND
v(MIC-LN)
PINS
AUXO)
Product specification
, which corresponds
HFTX
TEA1097
, G
v(IR-RECO)
AND
and