LS256 Datasheet, PDF (1/8 Pages) STMicroelectronics – TELEPHONE SPEECH CIRCUIT WITH MULTIFREQUENCY TONE GENERATOR INTERFACE

LS256
TELEPHONE SPEECH CIRCUIT WITH MULTIFREQUENCY
TONE GENERATOR INTERFACE
. PRESENTS THE PROPER DC PATH FOR THE
LINE CURRENT
. HANDLES THE VOICE SIGNAL, PERFORM-
ING THE 2/4 WIRES INTERFACE AND
CHANGING THE GAIN ON BOTH SENDING
AND RECEIVING AMPLIFIERS TO COMPEN-
SATE FOR LINE ATTENUATION BY SENSING
. THELINE LENGTHTHROUGH THE LINE CUR-
RENT
ACTS AS LINEAR INTERFACE FOR MF, SUP-
PLYING A STABILIZEDTO THE DIGITAL CHIP
AND DELIVERING TO THE LINE THE MF
TONE GENERATED BY THE DIALER
DIP16
SO20
ORDERING NUMBERS :
LS256B
LS256D
DESCRIPTION
The LS256 is a monolithic integrated circuit in 16-
lead dual in-line and SO20 plastic packages to re-
placethe hybridcircuit in telephoneset.It workswith
the same type of transdurcers for both transmitter
and receiver (typically piezoceramic capsules, but
PIN CONNECTIONS (top view)
the device can work also with dynamic ones). Many
of its electrical characteristics can be controlled by
means of external components to meet different
specifications.
In addition to the speech operation, the LS256 acts
as an interface for the MF tone signal.
DIP16
November 1996
N.C.
MIC. INPUT
+LINE
MUTING
BIAS ADJ.
SHUNT REG. BYPASS
DC. REGULATOR
LINE CURRENT SENSING
GAIN CONTROL
N.C.
1
20
2
19
3
18
4
17
5
16
6
15
7
14
8
13
9
12
10
11
D96TL274
SO20
N.C.
MIC. INPUT
V_DD
MF INPUT
RECEIVER OUTPUT
RECEIVER OUTPUT
INPUT+(REC.AMP.)
INPUT-(REC.AMP.)
-LINE
N.C.
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