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- Total 5 Pages 8/14/2006 Wrote by 2006 BL1240 Pin connection 8 7 6 5 BL1240 1 2 3 4 Pin Symble Function Description 1 LINE Telephone line 2 GND Ground 3 Csw Sweep rate control capacitor 4 RA Output frequency control resistor 5 OUT Output frequency frequency 6 NC Not connected 7 Cr Rectifier capacitor 8 LINE Telephone line http://www.belling.com.cn -2- Total 5 Pages 8/14/2006 Wrote by 2006 BL1240 BLOCK DIAGRAM TELEPHONE LINE 8 RECTIFIER CAPACITOR N.C. 6 BUZZER 5 THRESHOLD CIRCUIT WITH HYSTERESIS OUTPUT STAGE SWITCHING FREQUENCY GENERATOR TONE FREQUENCY GENERATOR 3 4 7 IN + RECTIFIER BRIDGE IN 1 2 TELEPHONE LINE GND SWEEP RATE CONTROL CAPACITOR OUTPUT FREQUENCY CONTROL RESISTOR Figure 1 : Test Circuit 1 uF 2.2 k 8 VAB LINE 1 Vs 2.72 ⋅10 4 f1 ⋅ (1 − 0.04 ln ) f 1 ( Hz ) 1943 http://www.belling.com.cn RL 7 10 uF R1 = 5 2 3 C1 100 uF 4 R1 14 k f 2 = 0.725 f 1 -3- Total 5 Pages VOUT f SWEEP = 750 C1 (nF ) 8/14/2006 Wrote by 2006 BL1240 ABSOLUTE MAXIMUM RATING Parameter Symbol Value Unit VAB(ON) 120 Vrms VAB(ON/OFF) 200 Vrms IDC 30 mA Operating Temperature Tamb -20 to +70 °C Storage and Junction Temperature Tstg -65 to +150 °C Calling Voltage (f = 50 Hz) Continuous Calling Voltage (f = 50 Hz) 5s ON/10s OFF DC Supply Current ( Ta = 25 °C unless otherwise specified ) RECOMMENDED OPERATING CONDITION ( Ta = 25 °C unless otherwise specified ) Parameter Symbol Calling Voltage (f = 50 Hz) Continuous Min. VAB (ON) Typ. Max. 75 Unit 120 Vrms ELECTRICAL CHARACTERISTICS ( Ta = 25 °C ) Parameter Symbol Max. Unit 26 V 1.8 mA 12.2 13.2 V VOFF 8 9 V RD 6.4 DC Power Supply Voltage VDC Current Consumption without Load (pins 8-1) IDCO Activation Voltage VON Sustaining Voltage Differential Resistance in OFF Condition (pins 8-1) Test Conditions Min. VDC = 9.3 to 2.5 V Typ. 1.5 Output Voltage Swing VOUT Short Circuit Current (pins 5-2) IOUT VDC = 20 V, RL = 250 Ω f1 VDC = 26 V, RA = 14 kΩ, V3 = 0V 1.74 f2 VDC = 26 V, RA = 14 kΩ, V3 = 6V kΩ VDC - 5 V 70 mA AC OPERATION Output Frequency Output Frequency f1 / f2 Sweep Frequency http://www.belling.com.cn VDC = 26 V, RA = 14 kΩ, Csw = 0.1 uF f sw -4- Total 5 Pages 2.14 kHz 1.22 1.6 kHz 1.33 1.43 7.5 Hz 8/14/2006 Wrote by 2006 BL1240 Figure 2 : Typical Application with BUZZER 1 uF 2.2 k 8 LINE 5 7 2 1 10 uF 3 BUZZER ZLOAD> 1kohm 4 C1 100 uF R1 14 k Figure 3: Typical Application with Loudspeaker (no transformer needed) 1 uF 2.2 k C1 8 LINE 10 uF 5 7 1 2 3 C1 100 uF 4 RL = 50 Ω to 1000 Ω R1 14 k C1 such that | Z LOAD | > 1 kΩ http://www.belling.com.cn -5- Total 5 Pages 8/14/2006 Wrote by 2006