LS256

November 1996

TONE GENERATOR INTERFACE

TELEPHONE SPEECH CIRCUIT WITH MULTIFREQUENCY

.

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 LENGTH THROUGH 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

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

DIP16

ORDERING NUMBERS :

LS256B

LS256D

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.

PIN CONNECTIONS (to p view)

DIP16

SO20

N.C.

MIC. INPUT

+LINE

MUTING

BIAS ADJ.

DC. REGULATOR

SHUNT REG. BYPASS

LINE CURRENT SENSING

GAIN CONTROL

-LINE

INPUT-(REC.AMP.)

INPUT+(REC.AMP.)

RECEIVER OUTPUT

RECEIVER OUTPUT

MF INPUT

V

DD

MIC. INPUT

N.C.

1

3

2

4

5

6

7

8

9

18

17

16

15

14

12

13

11

19

10

20

N.C.

N.C.

D96TL274

SO20

1/8