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LS1240A

Wing Shing Computer Components
Part Number LS1240A
Manufacturer Wing Shing Computer Components
Description Electronic Two-Tone Ringer
Published Apr 25, 2005
Detailed Description LS1240A Electronic Two-Tone Ringer . . . . . LOW CURRENT CONSUMPTION, IN ORDER TO ALLOW THE PARALLEL OPERATION OF 4 D...
Datasheet PDF File LS1240A PDF File

LS1240A
LS1240A

Overview
LS1240A Electronic Two-Tone Ringer .
.
.
.
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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 ADJUSTABLE BY EXTERNAL COMPONENTS INTEGRATED VOLTAGE AND CURRENT HYSTERESIS Minidip DESCRIPTION LS1240A is a monolithic integrated circuit designed 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 dynamic loudspeaker.
The output current capability of LS1240A is higher than standard ringer.
For driving a dynamic loudspeaker LS1240A can simply use a decoupling capacitor, thus eliminating the usual transformer.
No current limitation is provided on the output stage of LS1240A, so a minimum load DC of 50 Ω is adviced, in series with a proper capacitor.
The two tone frequencies generated are switched by an internal oscillator in a fast sequence and made audible across an output amplifier in the loudspeaker, both tone frequencies and the switching frequency can be externally adjusted.
PIN CONNECTION (top view) SO8 ORDERING NUMBERS Minidip LS1240A SO8 LS1240AD1 The supply voltage is obtained from the AC 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.
Wing Shing Computer Components Co.
, (H.
K.
)Ltd.
Homepage: http://www.
wingshing.
com Tel:(852)2341 9276 Fax:(852)2797 8153 E-mail: wsccltd@hkstar.
com WS BLOCK DIAGRAM LS1240A Figure 1 : Test Circuit.
R1 = 2.
72 ⋅ 104 f1 ⋅ ( 1 − 0.
04 ln ) 1943 f1 (Hz) f2 = 0.
725 f1 fSWEEP = 750 C1 (nF) WS ABSOLUTE MAXIMUM RATINGS Symbol VAB VAB DC Top Tstg Parameter Calling Voltage (f = 50 Hz) Continuous Calling Voltage (f = 50 Hz) 5s ON/10s OFF Supply Current Operating Temperature Storage and Junction Temperature Value 120 200 30 –20 to + 70 – 65 to + 150 LS1240A U...


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