L3240 Datasheet, PDF (1/6 Pages) STMicroelectronics – ELETRONIC TWO-TONE RINGER

L3240
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
Minidip
SO8
ORDERING NUMBERS : L3240B1 (Minidip)
L3240D1 (SO8)
DE SCRI P TI O N
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)
June 1993
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