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| BL1240 ELECTRONIC TWO - TONE RINGER Features 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. Description BL1240 is a monolithic integrated circuit designed to repace 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 BL1240 is higher than standard ringer. For driving a dynamic loud-speaker BL1240 can simply use a decoupling capacitor, thus eliminating the usual transformer. No current limitation is provided on the output stage of BL1240, so a minimum load DC of 50 ohm 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 loud-speaker, both tone frequencies and the switching frequency can be externally adjusted. The supply voltage is obtained from the AC ring signal and the circuit is designed so that noise on the line or variatins of the ringing signal cannot affect correct operation of the device. http://www.belling.com.cn -1- 8/14/2006 Wrote by 2006 Total 5 Pages BL1240 Pin connection 8 7 6 5 BL1240 1 2 3 4 Pin 1 2 3 4 5 6 7 8 Symble LINE GND Csw RA OUT NC Cr LINE Function Description Telephone line Ground Sweep rate control capacitor Output frequency control resistor frequency Output frequency Not connected Rectifier capacitor Telephone line http://www.belling.com.cn -2- 8/14/2006 Wrote by 2006 Total 5 Pages BL1240 BLOCK DIAGRAM TELEPHONE LINE 8 IN RECTIFIER CAPACITOR 7 N.C. 6 THRESHOLD CIRCUIT WITH HYSTERESIS BUZZER 5 + RECTIFIER BRIDGE OUTPUT STAGE IN SWITCHING FREQUENCY GENERATOR TONE FREQUENCY GENERATOR 1 TELEPHONE LINE 2 GND 3 SWEEP RATE CONTROL CAPACITOR 4 OUTPUT FREQUENCY CONTROL RESISTOR Figure 1 : Test Circuit 1 uF 2.2 k 8 VAB LINE 10 uF Vs 7 1 2 C1 100 uF 5 RL 3 4 R1 14 k VOUT R1 = 2.72 10 4 f1 (1 - 0.04 ln ) f 1 ( Hz ) 1943 f 2 = 0.725 f 1 f SWEEP = 750 C1 (nF ) http://www.belling.com.cn -3- 8/14/2006 Wrote by 2006 Total 5 Pages BL1240 ABSOLUTE MAXIMUM RATING Parameter Calling Voltage (f = 50 Hz) Continuous Calling Voltage (f = 50 Hz) 5s ON/10s OFF DC Supply Current Operating Temperature Storage and Junction Temperature ( Ta = 25 C unless otherwise specified ) Symbol VAB(ON) VAB(ON/OFF) IDC Tamb Tstg Value 120 200 30 -20 to +70 -65 to +150 Unit Vrms Vrms mA C C RECOMMENDED OPERATING CONDITION ( Ta = 25 C unless otherwise specified ) Parameter Calling Voltage (f = 50 Hz) Continuous Symbol VAB (ON) Min. Typ. Max. 75 120 Unit Vrms ELECTRICAL CHARACTERISTICS ( Ta = 25 C ) Parameter DC Power Supply Voltage Current Consumption without Load (pins 8-1) Activation Voltage Sustaining Voltage Differential Resistance in OFF Condition (pins 8-1) Output Voltage Swing Short Circuit Current (pins 5-2) AC OPERATION VDC = 26 V, RA = 14 k, V3 = 0V VDC = 26 V, RA = 14 k, V3 = 6V Symbol VDC IDCO VON VOFF RD VOUT IOUT VDC = 20 V, RL = 250 VDC = 9.3 to 2.5 V 12.2 8 Test Conditions Min. Typ. Max. 26 Unit V 1.5 1.8 13.2 9 mA V V k 6.4 VDC - 5 70 V mA Output Frequency f1 1.74 2.14 kHz Output Frequency f2 f1 / f2 1.22 1.33 1.6 1.43 kHz Sweep Frequency f sw VDC = 26 V, RA = 14 k, Csw = 0.1 uF 7.5 Hz http://www.belling.com.cn -4- 8/14/2006 Wrote by 2006 Total 5 Pages BL1240 Figure 2 : Typical Application with BUZZER 1 uF 2.2 k 8 LINE 10 uF 7 1 2 C1 100 uF 5 BUZZER ZLOAD> 1kohm 3 4 R1 14 k Figure 3: Typical Application with Loudspeaker (no transformer needed) 1 uF 2.2 k C1 8 LINE 10 uF 7 1 2 C1 100 uF 5 3 4 RL = 50 to 1000 R1 14 k C1 such that | Z LOAD | > 1 k http://www.belling.com.cn -5- 8/14/2006 Wrote by 2006 Total 5 Pages |
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