TEA1093T Philips Semiconductors, TEA1093T Datasheet - Page 6

• Manufacturer Part Number: TEA1093T
• Description: Hands-free IC
• Manufacturer: Philips Semiconductors

Philips Semiconductors
FUNCTIONAL DESCRIPTION
The values given in the functional description are typical
values except when otherwise specified.
A principle diagram of the TEA106X is shown on the left
side of Fig.3. The TEA106X is a transmission circuit of the
TEA1060 family intended for hand-set operation. It
incorporates a receiving amplifier for the earpiece, a
transmit amplifier for the microphone and a hybrid. For
more details on the TEA1060 family, please refer to “Data
Handbook IC03” . The right side of Fig.3 shows a principle
diagram of the TEA1093, a hands-free add-on circuit with
a microphone amplifier, a loudspeaker amplifier and a
duplex controller.
As can be seen from Fig.3, a loop is formed via the
sidetone network in the transmission circuit and the
acoustic coupling between loudspeaker and microphone
of the hands-free circuit. When this loop gain is greater
than 1, howling is introduced. In a full duplex application,
1996 Feb 09
handbook, full pagewidth
Hands-free IC
telephone
line
sidetone
Fig.3 Hands-free telephone set principles.
TEA106X
HYBRID
CONTROL
TEA1093
DUPLEX
6
this would be the case. The loop-gain has to be much
lower than 1 and therefore has to be decreased to avoid
howling. This is achieved by the duplex controller.The
duplex controller of the TEA1093 detects which channel
has the ‘largest’ signal and then controls the gain of the
microphone amplifier and the loudspeaker amplifier so that
the sum of the gains remains constant. As a result, the
circuit can be in three stable modes:
1. Transmit mode (Tx mode): the gain of the microphone
2. Receive mode (Rx mode): the gain of the loudspeaker
3. Idle mode: the gain of the amplifiers is halfway
The difference between the maximum gain and minimum
gain is called the switching range.
amplifier is at its maximum and the gain of the
loudspeaker amplifier is at its minimum.
amplifier is at its maximum and the gain of the
microphone amplifier is at its minimum.
between their maximum and minimum value.
MGD218
coupling
acoustic
Product specification
TEA1093