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| LS1240A Electronic Two-Tone Ringer .LOW .I .LI .TONE .I CURRENT CONSUMPTION, IN ORDER TO ALLOW THE PARALLEL OPERATION OF 4 DEVICES NTEGRATED RECTIFIER BRIDGE WITH ZENER DIODES TO PROTECT AGAINST OVERVOLTAGES TTLE EXTERNAL CIRCUITRY AND SWITCHING FREQUENCIES ADJUSTABLE BY EXTERNAL COMPONENTS NTEGRATED 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 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 Unit Vrms Vrms mA C C THERMAL DATA Symbol Rth j-amb Parameter Thermal Resistance Junction-ambient Max Value Unit C/W 2 00 ELECTRICAL CHARACTERISTICS (Tamb = 25 C; Vs = applied between pins 7-2 unless otherwise specified) Symbol Vs IB VON VOFF RD VOUT IOUT 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) Vs = 20V RL = 250 V8-1 = 9.3 to 25 V 12 Parameter Test Conditions Min. Typ. 1.5 Max. 26 1.8 Unit V mA 13.5 7.8 6.4 Vs - 5 70 9.3 V V k V mA kHz AC OPERATION f1 f2 Output Frequencies fout1 fout2 fOUT1 fOUT2 Programming Resistor Range fSWEEP Sweep Frequency R1 = 14k, C1 = 100nF Vs = 26V, R1 = 14k Vs = 0 V Vs = 6V 1.55 1.08 1.33 8 5.25 7.5 2.53 1.9 1.43 56 9.75 k Hz WS Figure 2 : Typical Application with BUZZER LS1240A Figure 3 : Typical Application with Loudspeaker (no transformer needed) C1 such that ZLOAD > 1 |
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