Overview
The LS1240AD1 is a monolithic integrated circuit designed by STMicroelectronics to replace mechanical bells in telephone sets. It is integrated with an electro-acoustical converter and can drive either a piezoceramic converter (buzzer) or a dynamic loudspeaker directly. This IC is notable for its low current consumption, allowing the parallel operation of up to four devices, and its integrated rectifier bridge with zener diodes to protect against overvoltages. The device operates using the AC ring signal and is designed to be resilient against noise on the line or variations in the ringing signal.
Key Specifications
| 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 | Current consumption without load (pins 8-1) | 1.5 - 1.8 | mA |
| TOP | Operating temperature | -40 to 70 | °C |
| Tstg | Storage and junction temperature | -65 to +150 | °C |
| VON | Activation voltage | 12.2 - 13.2 | V |
| VOFF | Sustaining voltage | 8 - 9 | V |
| RD | Differential resistance in OFF conditions (pins 8-1) | 6.4 kΩ | kΩ |
| VOUT | Output voltage swing | Vs - 5 V | V |
| IOUT | Short circuit current (pins 5-2) | 70 mA | mA |
| f1, f2 | Output frequencies | 1.74 kHz, 1.22 kHz (typical) | kHz |
| fSWEEP | Sweep frequency | 5.25 - 9.75 Hz | Hz |
Key Features
- Low current consumption, allowing parallel operation of up to four devices.
- Integrated rectifier bridge with zener diodes to protect against overvoltages.
- Tone and switching frequencies adjustable by external components.
- Integrated voltage and current hysteresis.
- Can drive directly a piezoceramic converter (buzzer) or a dynamic loudspeaker without the need for a transformer.
- High output current capability compared to standard ringers.
- Designed to operate from the AC ring signal, resilient against noise and variations in the ringing signal.
Applications
The LS1240AD1 is primarily used in telephone sets to replace mechanical bells. It is suitable for any application requiring a two-tone ringer, such as:
- Telephone handsets and landline phones.
- Intercom systems.
- Alarm systems requiring audible alerts.
- Other communication devices needing a reliable and adjustable ringer function.
Q & A
- What is the primary function of the LS1240AD1 IC?
The LS1240AD1 is designed to replace mechanical bells in telephone sets, providing a two-tone ringer function.
- What types of speakers can the LS1240AD1 drive?
The LS1240AD1 can drive both piezoceramic converters (buzzers) and dynamic loudspeakers.
- How does the LS1240AD1 protect against overvoltages?
The IC includes an integrated rectifier bridge with zener diodes to protect against overvoltages.
- Can the tone and switching frequencies be adjusted?
- What is the recommended minimum load for the output stage?
A minimum load DC of 50 Ω is advised, in series with a proper capacitor.
- What is the operating temperature range of the LS1240AD1?
The operating temperature range is -40 to +70 °C.
- How does the LS1240AD1 handle noise on the line or variations in the ringing signal?
The circuit is designed to be resilient against noise on the line or variations in the ringing signal.
- What are the typical output frequencies of the LS1240AD1?
The typical output frequencies are around 1.74 kHz and 1.22 kHz.
- What is the sweep frequency range of the LS1240AD1?
The sweep frequency range is approximately 5.25 to 9.75 Hz.
- What package types are available for the LS1240AD1?
The LS1240AD1 is available in Minidip and SO8 packages.
