Wing Shing LS1240A, LS1240AD1 Datasheet

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Electronic

Two-Tone Ringer

LS1240A

LOW CURRENT CONSUMPTION, IN ORDER
TO ALLOW THE P ARALLEL OPERATION O F 4
DEVICES

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INTEGRATED RECTIFIER BRIDGE WITH
ZENER DIODES TO PROTECT AGAINST
OVERVOLTAGES

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LITTLE EXTERNAL CIRCUITRY

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TONE AND SWITC HING FREQUEN CIES AD­JUSTABLE BY EXTERNAL COMPONENTS

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INTEGRATED VOLTAGE AND CURRENT
HYSTERESIS

DESCRIPTION

LS1240A is a mon olith ic in tegrated circ uit de signed
to replace the mechanical bell in telephone sets in
connection with an electro-acoustical converter. It
can drive directly a piezoceramic converter (buzz­er)or a dynam ic loudspe ak er .

The output current capability of LS1240A is higher
than standard ringer. For driving a dynamic loud­speaker LS 124 0A c an simply us e a dec oupling ca­pacitor, thus elim inating the us ual trans f or m er .

No curre nt limitation is provided on the outpu t stage
of LS1240A, so a minimum load DC of 50 Ω is ad­viced, in s er ies with a proper c apac itor.

The two tone frequencies generated are switched
by an inte rnal oscillator in a fas t sequence and m ade
audible across an output amplifier in the loud­speaker, both tone frequencies and the switching
frequency c an be externally adj us t ed.

Minidip

SO8

ORDERING NUMBERS

Minidip SO8

LS1240A LS1240AD1

The suppl y voltage is obtained from the A C ring sig­nal and the circuit is designed so that noise on the
line or variations of the ringing signal cannot affect
correct operation of the device.

PIN CONNECTION (top view)

Wing Shing Computer Components Co., (H.K.)Ltd. Tel:[phone] Fax:[phone]
Homepage: http://www.wingshing.com E-mail: [e-mail]

BLOCK DIAGRAM

WS

LS1240A

Figure 1 : Test Circuit.

2.72 ⋅ 10

R1 =

f1 (Hz)

4

⋅ (1 − 0.04 ln

f1

f2 = 0.725 f1 f

)

1943

SWEEP

=

C1 (nF)

750