![](http://datasheet.mmic.net.cn/370000/TEA1094_datasheet_16741359/TEA1094_7.png)
1996 Jul 15
7
Philips Semiconductors
Product specification
Hands free IC
TEA1094; TEA1094A
Fig.4 Hands-free telephone set principles.
handbook, full pagewidth
MGE438
DUPLEX
CONTROL
HYBRID
telephone
line
sidetone
acoustic
coupling
TEA106x
TEA1094
TEA1094A
Supply: pins V
BB
, GND and PD
The TEA1094 and TEA1094A must be supplied with an
external stabilized voltage source between pins V
BB
and
GND. In the idle mode, without any signal, the internal
supply current is 3.1 mA at V
BB
= 5 V.
To reduce the current consumption during pulse dialling or
register recall (flash), the TEA1094A is provided with a
power-down (PD) input. When the voltage on PD is HIGH
the current consumption from V
BB
is 180
μ
A.
Microphone channel: pins MIC, GAT, MOUT, MICGND
and MUTET
(see Fig.5)
The TEA1094 and TEA1094A have an asymmetrical
microphone input MIC with an input resistance of 20 k
.
The gain of the input stage varies according to the mode
of the TEA1094 and TEA1094A. In the transmit mode, the
gain is at its maximum; in the receive 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 output capability at pin MOUT is
20
μ
A (RMS).
In the transmit mode, the overall gain of the microphone
amplifier (from pins MIC to MOUT) can be adjusted from
0 dB up to 31 dB to suit specific application requirements.
The gain is proportional to the value of R
GAT
and equals
15.5 dB with R
GAT
= 30.1 k
.
A capacitor must be connected in parallel with R
GAT
to
ensure stability of the microphone amplifier. Together with
R
GAT
, it also provides a first-order low-pass filter.
By applying a HIGH level on pin MUTET, the microphone
amplifier is muted and the TEA1094 and TEA1094A are
automatically forced into the receive mode.