LS1240A STMICROELECTRONICS | Alldatasheet
Document overview
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Technical content
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
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. 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) Minidip SO8 Obsolete Product(s) - Obsolete Product(s) Obsolete Product(s) - Obsolete Product(s)
1 Block diagram and test circuit
Figure 1. LS1240 block diagram Figure 2. Test circuit
2 Electrical characteristics
Tamb = 25°C, VS = applied between pins 7-2 unless otherwise specified. Table 1. Absolute maximum ratings Table 2. Thermal data Table 3. Electrical characteristics
3 Application schematics
Figure 3. Typical application with buzzer Figure 4. Typical application with loudspeaker (no transformer needed)
Obsolete Product(s) - Obsolete Product(s) Obsolete Product(s) - Obsolete Product(s)
4 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. ECOP ACK is an ST trademark. ECOPACK specifications are available at: www.st.com.
Figure 5. Minidip package mechanicla drawing Table 4. Minidip package dimensions
Figure 6. SO8 mechanical drawing Table 5. SO8 package dimensions
5 Ordering information
6 Revision history
Table 6. Order codes
- ECOPACK ® (see Chapter 4)
Table 7. Document revision history 15-Jul-1998 1 Initial release. and part numbers have changed.