LS1240A

LS1240 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 over voltages little external circuitry ■ Tone and switching frequencies adjustable by external components ■ Integrated voltage and current hysteresis Minidip Description LS1240 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 LS1240 is higher than the one of a standard ringer. To drive a dynamic loudspeaker LS1240 can simply use a decoupling capacitor, thus eliminating the usual transformer. No current limitation is provided on the output stage of LS1240, so a minimum load DC of 50 Ω is advised, in series with a proper capacitor. SO8 The two tone frequencies generated are switched by an internal oscillator in a fast sequence and are made audible across an output amplifier in the loudspeaker. 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 variations of the ringing signal cannot affect correct operation of the device. Pin connection (top view) August 2006 Rev 2 1/9 www.st.com 9 Block diagram and test circuit 1 LS1240 Block diagram and test circuit Figure 1. LS1240 block diagram Telephone line 8 Rectifier bridge 1 Telephone line Figure 2. R1 = 2/9 Rectifier capacitor N.C. 7 Buzzer 5 6 + - Threshold circuit with hysteresis Output Switching frequency generator Tone frequency generator 2 GND stage 3 4 Sweep rate control capacitor Output frequency control resistor Test circuit 2.72 ⋅ 104 f1 ⋅ ( 1 − 0.04 ln ) 1943 f1 (Hz) f2 = 0.725 f1 fSWEEP = 750 C1 (nF) LS1240 2 Electrical characteristics Electrical characteristics Table 1. Absolute maximum ratings Symbol Parameter Value Unit VAB Calling voltage (f = 50 Hz) continuous 120 Vms VAB Calling voltage (f = 50 Hz) 5s ON/10s OFF 200 Vms DC Supply current 30 mA TOP Operating temperature -40 to 70 °C Tstg Storage and junction temperature -65 to +150 °C Value Unit 100 °C/W Table 2. Thermal data Symbol Rthj-amb Parameter Maximum thermal resistance junction-ambient Tamb = 25°C, VS = applied between pins 7-2 unless otherwise specified. Table 3. Electrical characteristics Symbol Parameter Test conditions Min. Typ. Max. unit 26 V 1.8 mA VS Supply voltage IB Current consumption without laod (pins 8-1) VON Activation voltage 12.2 13.2 V VOFF Sustaining voltage 8 9 V RD Differential resistance in OFF conditions (pins 8-1) VOUT Output voltage swing IOUT Short circuit current (pins 5-2) V8-1 = 9.3 to 25 V 1.5 6.4 VS = 20V RL = 250Ω kΩ VS-5 V 70 mA AC operation f1 f2 Output frequencies fOUT1 fOUT2 VS = 26V, R1 = 14Ω VS = 0V VS = 6V f OUT1 -----------f OUT2 Programming resistor range Sweep frequency R1 = 14 kΩ, C1 = 100 nF 1.74 1.22 2.14 1.6 1.33 1.43 8 56 kW 9.75 Hz 5.25 7.5 kHz 3/9 Application schematics 3 LS1240 Application schematics Figure 3. Typical application with buzzer Figure 4. Typical application with loudspeaker (no transformer needed) C1 such that ⏐ZLOAD ⏐ > 1 ΚΩ 4/9 LS1240 4 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect . The category of second Level Interconnect ismarked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com. 5/9 Package mechanical data Table 4. LS1240 Minidip package dimensions mm inch Dim. Min. A Typ. Min. 3.32 Typ. Max. 0.131 a1 0.51 0.020 B 1.15 1.65 0.045 0.065 b 0.356 0.55 0.014 0.022 b1 0.204 0.304 0.008 0.012 D E 10.92 7.95 9.75 0.430 0.313 0.384 e 2.54 0.100 e3 7.62 0.300 e4 7.62 0.300 F 6.6 0.260 I 5.08 0.200 L Z Figure 5. 6/9 Max. 3.18 3.81 1.52 Minidip package mechanicla drawing 0.125 0.150 0.060 LS1240 Package mechanical data Table 5. SO8 package dimensions mm inch Dim. Min. Typ. A a1 Max. Min. Typ. 1.75 0.1 0.25 a2 Max. 0.069 0.004 0.010 1.65 0.065 a3 0.65 0.85 0.026 0.033 b 0.35 0.48 0.014 0.019 b1 0.19 0.25 0.007 0.010 C 0.25 0.50 0.010 0.020 c1 45° (typ.) D(1) 4.8 5.0 0.189 0.197 E 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 3.81 0.150 F(1) 3.8 4.0 0.15 0.157 L 0.4 1.27 0.016 0.050 M 0.6 S Figure 6. 0.024 8° (max.) SO8 mechanical drawing 7/9 Ordering information 5 LS1240 Ordering information Table 6. Order codes Part number Package LS1240A Minidip LS1240AD1 SO8 (1) E-LS1240A Minidip E-LS1240AD1(1) SO8 ® 1. ECOPACK (see Chapter 4) 6 Revision history Table 7. 8/9 Document revision history Date Revision Changes 15-Jul-1998 1 Initial release. 23-Aug-2006 2 Updated the document to reflect the fact that packages are leadfree and part numbers have changed. LS1240 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. 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