tea1094t NXP Semiconductors, tea1094t Datasheet - Page 12

• Manufacturer Part Number: tea1094t
• Description: Hands Free Ic
• Manufacturer: NXP Semiconductors

Philips Semiconductors
As can be seen from Fig.9, the output of the decision logic
is a current source. The logic table gives the relationship
between the inputs and the value of the current source.
It can charge or discharge the capacitor C
current of 10 A (switch-over). If the current is zero, the
voltage on SWT becomes equal to the voltage on IDT via
the high-ohmic resistor R
difference between SWT and IDT determines the mode of
the TEA1094 (TEA1094A) and can vary between
Table 1 Modes of TEA1094; TEA1094A
The switch-over timing can be set with C
timing with C
Fig.13, C
switch-over time from transmit to receive mode or
vice-versa of approximately 13 ms (580 mV swing on
SWT). The switch-over time from idle mode to transmit
mode or receive mode is approximately 4 ms (180 mV
swing on SWT).
The switch-over time, from receive mode or transmit mode
to idle mode, is equal to 4
approximately 2 seconds (idle mode time).
The inputs MUTET and DLC/MUTER overrule the decision
logic. When MUTET goes HIGH, the capacitor C
charged with 10 A thus resulting in the receive mode.
When the voltage on pin DLC/MUTER goes lower than
0.2 V, the capacitor C
resulting in the transmit mode.
V
A diagram of the voice-switch is illustrated in Fig.10. With
the voltage on SWT, the TEA1094 (TEA1094A)
voice-switch regulates the gains of the transmit and the
receive channel so that the sum of both is kept constant.
In the transmit mode, the gain of the microphone amplifier
is at its maximum and the gain of the loudspeaker amplifier
is at its minimum. In the receive mode, the opposite
applies. In the idle mode, both microphone and
loudspeaker amplifier gains are halfway.
1996 Jul 15
< 180
0
>180
400 and +400 mV (see Table 1).
OICE
Hands free IC
V
SWT
-
SWITCH
SWT
V
SWT
IDT
is 220 nF and R
:
PINS
(mV)
and R
STAB
SWT
IDT
IDT
. In the basic application given in
transmit mode
idle mode
receive mode
is discharged with 10 A thus
AND
(idling). The resulting voltage
R
IDT
IDT
SWR
is 2.2 M . This enables a
C
SWT
MODE
and is
SWT
SWT
, the idle mode
with a
SWT
is
12
The difference between maximum and minimum is the so
called switching range. This range is determined by the
ratio of R
0 and 52 dB. R
internally used reference current. In the basic application
diagram given in Fig.13, R
switching range of 40 dB. The switch-over behaviour is
illustrated in Fig.11.
In the receive mode, the gain of the loudspeaker amplifier
can be reduced using the volume control. Since the
voice-switch keeps the sum of the gains constant, the gain
of the microphone amplifier is increased at the same time
(see dashed curves in Fig.11). In the transmit mode,
however, the volume control has no influence on the gain
of the microphone amplifier or the gain of the loudspeaker
amplifier. Consequently, the switching range is reduced
when the volume is reduced. At maximum reduction of
volume, the switching range becomes 0 dB.
The pin numbers given in parenthesis refer to the TEA1094A.
(1) C = constant.
volume
control
SWR
from
and R
DUPLEX CONTROLLER
microphone
STAB
amplifier
G vtx
VOICE SWITCH
to
Fig.10 Voice switch.
loudspeaker
STAB
should be 3.65 k and sets an
amplifier
G vrx
TEA1094; TEA1094A
to
and is adjustable between
SWR
SWT
from
C
(1)
is 365 k which results in a
STAB
SWR
MGD225
Product specification
(10)
(9)
12
13
R STAB
R SWR