LS1240A . . .. . Electronic Two-Tone Ringer 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 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. Minidip SO8 ORDERING NUMBERS Minidip LS1240A 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. PIN CONNECTION (top view) Wing Shing Computer Components Co., (H.K.)Ltd. Homepage: http://www.wingshing.com SO8 LS1240AD1 Tel:(852)2341 9276 Fax:(852)2797 8153 E-mail: [email protected] WS LS1240A BLOCK DIAGRAM 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 LS1240A ABSOLUTE MAXIMUM RATINGS Symbol Parameter Value Unit VAB Calling Voltage (f = 50 Hz) Continuous 120 Vrms VAB Calling Voltage (f = 50 Hz) 5s ON/10s OFF 200 Vrms DC Supply Current 30 mA Top Operating Temperature –20 to + 70 Tstg Storage and Junction Temperature – 65 to + 150 °C Value Unit °C THERMAL DATA Symbol Rth j-amb Parameter Thermal Resistance Junction-ambient Max °C/W 2 00 ELECTRICAL CHARACTERISTICS (Tamb = 25 °C; Vs = applied between pins 7-2 unless otherwise specified) Symbol Parameter Vs Supply Voltage IB Current Consumption without Load (pins 8-1) Test Conditions Min. V8-1 = 9.3 to 25 V Typ. 1.5 Max. V 1.8 mA V V kΩ V mA VON Activation Voltage 12 13.5 VOFF Sustaining Voltage 7.8 9.3 Differential Resistance in OFF Condition (pins 8-1) 6.4 RD VOUT Output Voltage Swing IOUT Short Circuit Current (pins 5-2) Vs – 5 Vs = 20V 70 RL = 250Ω Unit 26 AC OPERATION f1 f2 Output Frequencies fout1 fout2 Vs = 26V, R1 = 14kΩ Vs = 0 V Vs = 6V fOUT1 fOUT2 Programming Resistor Range fSWEEP Sweep Frequency R1 = 14kΩ, C1 = 100nF kHz 1.55 1.08 1.33 2.53 1.9 1.43 8 56 kΩ 9.75 Hz 5.25 7.5 WS LS1240A Figure 2 : Typical Application with BUZZER Figure 3 : Typical Application with Loudspeaker (no transformer needed) C1 such that ZLOAD > 1 ΚΩ