LS1240A LINEAR INTEGRATED CIRCUIT
1
ELECTRONIC TONE RINGER WITH
BUILT-IN BRIDGE RECTIFIER
DESCRIPTION
The Contek LS1240A is amonolithic integrated circuit,
designed to be as a telephone ringer . It can drive directly a
piezo-ceramic converter (buzzer). The output current
capacitity of Contek LS1240A is higher than Contek LS1240, For
driving a dynamic loudspeaker , Contek LS1240A needs only a
decoupling capacitor.
FEATURES
*Low current consumption, in order to allow the parallel
operation of 4 devices.
*Integrated rectifier bridge with zener diodes to protect
against over voltage.
*Little external circuitry.
*Tone and switching frequencies adjustable by external
components.
*Integrated voltage and current hysteresis.
DIP-8
TEST CIRCUIT
f1= 27200
R1(k W)
f2=0.725f1 f ( SWEEP )= 750
C1(nF)
2.2k W
1mF
10 mF
C1
100nF
R1
14k W
RL VoutVAB
85
7
1234
Contek
LS1240A
CONTEK
Contek Microelectronics Co.,Ltd.
http://www.contek-ic.com E-mail:sales@contek-ic.com
LS1240A LINEAR INTEGRATED CIRCUIT
2
ABSOLUTE MAXIMUM RATINGS(Ta=25 C)
PARAMETER SYMBOL VALUE UNIT
Calling Voltage(f=50Hz)
Continuous
VAB 120 Vrms
Calling Voltage(f=50Hz)
5s ON/10s OFF
VAB 200 Vrms
Supply Current IDC 30 mA
Operating Temperature Topr -20 ~ +70 C
Storage Temperature Tstg -65 ~ +150 C
Thermal Resistance
Junction-Ambient
Rth-amb 200 C/W
ELECTRICAL CHARACTERISTICS
(Ta=25 C, unless otherwise specified)
PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT
Supply Voltage Vs26 V
Current Consumption
Without load
IBVs=9.3 to 25V 1.5 1.8 mA
Activation Voltage : 1240 Von 12 13.5 V
1240A Von 12 13.5 V
Sustaining Voltage :1240 VOFF 89V
1240A 7.8 9.3 V
Differential Resistance
in OFF Condition
RD6.4 kW
Output Voltage Swing Vout Vs-5 V
Short Circuit Current
1240 Iout Vs=20V,RL=0 W89V
1240A RL=250W7.8 9.3 V
AC Operation
Output Frequenies : Vs=26V,R1=14k W
1240 fout1 V3=0V 1.65 2.53 kHz
fout2 Vs=6V 1.15 1.9 kHz
1240A fout1 V3=0V 1.55 2.53 kHz
fout2 Vs=6V 1.08 1.9 kHz
Fout1/Fout2 1.33 1.43 kHz
Programming Resistor Range 8 5.6 kW
Sweep Frequency C1=100nF,R1=14k W5.25 7.5 9.75 Hz
CONTEK
Contek Microelectronics Co.,Ltd.
http://www.contek-ic.com E-mail:sales@contek-ic.com
LS1240A LINEAR INTEGRATED CIRCUIT
3
PIN CONFIGURATIONS
1
2
3
4
8
7
6
5
LINE
GROUND
SWEEP RATE
CONTROL
CAPACITOR
OUTPUT
FREQUENCY
CONTROL
RESISTOR
LINE
RECTIFIER
CAPACITOR
NULL
BUZZER
APPLICATION CIRCUIT
2.2kW
1mF
10 mF
C1
100nF
R1
14kW
LINE
BUZZER
Zload>1k
W
58
7
123 4
Contek LS1240
2.2kW
1mF
10 mF
C1
100nF
R1
14kW
LINE
85
7
1234
CL
RL=50Wto
1000W
ContekLS1240A
No current limitation is provided on the output stage of Contek LS1240A ,so a minimum load DC of 50 ohms is
adviced.
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.The signal and the circuit is designed so that noise on the lin or variations of the ringing signal cannot affect
correct operation of the device.
Contek
CONTEK
Contek Microelectronics Co.,Ltd.
http://www.contek-ic.com E-mail:sales@contek-ic.com
