The **LSMT2-10140-R** is a high-performance, surface-mount (SMT) magnetic transducer (buzzer) commonly used in consumer electronics, medical devices, and security systems for audible signaling. --- ### 1. Key Technical Specifications The following table highlights the critical electrical and physical parameters of the component: | Parameter | Specification | | :--- | :--- | | **Type** | Magnetic Transducer (External Drive) | | **Rated Voltage** | 3.6 Vo-p | | **Operating Voltage** | 2.5 ~ 4.5 Vo-p | | **Rated Current** | Max 100 mA | | **Sound Pressure Level (SPL)** | Min 87 dB (at 10cm) | | **Resonant Frequency** | 2,700 Hz | | **Coil Resistance** | 15 ± 3 Ω | | **Operating Temperature** | -40°C to +85°C | | **Dimensions** | 10.0 x 10.0 x 4.0 mm | --- ### 2. Electronic Components & Working Principle The LSMT2-10140-R is an **external drive** magnetic buzzer, meaning it does not have an internal oscillation circuit. To produce sound, it requires an external AC signal (usually a square wave). * **Internal Coil:** A fine copper wire coil wrapped around a core. When current passes through, it creates a fluctuating magnetic field. * **Permanent Magnet:** Provides a static magnetic field that interacts with the coil's field. * **Vibrating Diaphragm:** A metal disk that moves rapidly in response to the magnetic fluctuations, pushing air to create sound waves at the resonant frequency (2.7 kHz). * **SMT Housing:** High-temperature plastic (usually LCP) designed to withstand reflow soldering processes. --- ### 3. Application Circuitry Because this is a magnetic transducer, it is sensitive to DC bias. A typical driver circuit involves: 1. **Transistor Switch:** A NPN transistor or MOSFET is used to switch the current through the buzzer. 2. **Flyback Diode:** A diode (like 1N4148) should be placed in parallel with the buzzer to protect the circuit from voltage spikes caused by the inductor coil. 3. **PWM Signal:** A microcontroller (MCU) must provide a 2.7 kHz PWM signal to reach the maximum volume. ```c // Pseudo-code for MCU Drive Frequency = 2700Hz; Duty_Cycle = 50%; Timer_Start(PWM_PIN, Frequency, Duty_Cycle); ``` --- ### 4. Advantages * **Low Profile:** The 4.0mm height is ideal for thin portable devices. * **Durability:** Magnetic buzzers generally offer a longer lifespan and better environmental resistance than piezo equivalents in high-vibration settings. * **SMD Compatibility:** Fully compatible with automated pick-and-place machines and lead-free reflow soldering.