The **LSMT2-22140-R** is a high-performance, surface-mount (SMT) magnetic buzzer/transducer designed for applications requiring a compact footprint and high sound pressure levels. --- ### 1. Technical Specifications The following table outlines the primary electrical and physical characteristics of the component: | Feature | Specification | | :--- | :--- | | **Rated Voltage** | 12.0 Vp-p | | **Operating Voltage** | 7.0 ~ 16.0 Vp-p | | **Rated Current** | Max. 40 mA | | **Sound Pressure Level (SPL)** | Min. 85 dB (at 10cm) | | **Resonant Frequency** | 2400 Hz | | **Coil Resistance** | 140 ± 14 Ω | | **Operating Temperature** | -40°C to +85°C | | **Mounting Type** | Surface Mount (SMD/SMT) | --- ### 2. Electronic Functionality The LSMT2-22140-R is a **Magnetic Transducer**, which differs from a "piezo" or a "self-driven" buzzer in several ways: * **Electromagnetic Induction:** It consists of a coil of wire, a permanent magnet, and a vibrating metal diaphragm. When an oscillating current passes through the coil, it creates a fluctuating magnetic field that moves the diaphragm to produce sound. * **External Drive Required:** This is a transducer, not an indicator. It does **not** have internal circuitry. To produce sound, the engineer must provide a square wave signal (typically at the resonant frequency of 2400Hz). * **Polarity:** While some magnetic buzzers are non-polar, most SMT versions have a polarity mark (+) on the casing to ensure correct phase and integration into the circuit. --- ### 3. Application Circuitry Because this part requires a peak-to-peak voltage and consumes up to 40mA, it is rarely driven directly by a Microcontroller (MCU) GPIO pin. **Standard Drive Circuit Components:** 1. **Switching Transistor:** A NPN transistor or N-Channel MOSFET is used to switch the buzzer on and off at the target frequency. 2. **Flyback Diode:** Since the part contains a coil (inductor), a diode should be placed in parallel with the buzzer to protect the circuit from voltage spikes when the transistor switches off. 3. **Current Limiting:** Ensure the peak current does not exceed the rated 40mA to prevent coil burnout. --- ### 4. Typical Use Cases * **Medical Devices:** Alarms and status indicators for portable monitors. * **Automotive:** Dashboard alerts, turn signal clicking, or proximity sensors. * **Consumer Electronics:** Household appliances (microwaves, washing machines) and handheld POS terminals.