L3240

June 1993

ELETRONIC TWO-TONE RINGER

.

LOW CURRENT CONSUMPTION, IN ORDER

TO ALLOW THE PARALLEL OPERATION OF 4

DEVICES

.

INTEGRATED RECTIFIER BRIDGE

WITH

ZENER DIODES TO PROTECT AGAINST

OVERVOLTAGES

.

LITTLE EXTERNAL CIRCUITRY

.

TONE AND SWITCHING FREQUENCIES AD-

JUSTABLE BY EXTERNAL COMPONENTS

.

INTEGRATED VOLTAGE AND CURRENT

HYSTERESIS

.

COMPLEMENTARY OUTPUT CONFIGURA-

TION

DESCRIPTION

L3240 is a monolithic integrated circuit designed to

replace the mechanical bell in telephone sets, in

connectionwith an electro acoustical converter. The

device can drive either directly a piezo ceramic con-

verter (buzzer) or a small loudspeaker. In this case

a transformer is needed. The two tone frequencies

generated are switched by an internal oscillator in a

fast sequenceand made audible across output am-

plifiers in the transducer ; both tone frequencies and

the switching frequency can be externally adjusted.

The supply voltage is obtained from the AC ring sig-

nal and the circuit is designed so that noise on the

line or variations of the ringing signal cannot affect

the correct operation of the devices.

The output bridge configuration allows to use a high

impedance transducer with acoustical results much

better than in a single ended configuration.

The two outputs can also be connected inde-

pendently to

different

converters

or

actua-

tors (acoustical, opto, logic).

PIN CONNECTION ( top view)

Minidip

SO8

ORDERING NUMBERS : L3240B1 (Minidip)

L3240D1 (SO8)

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