### MJS 500-R Electronic Components & Specifications The **MJS 500-R** is a specific model of a **Miniature Surface Mount (SMT) Fuse** from the MJS series, typically manufactured by companies like Bel Fuse. It is designed for board-level primary and secondary circuit protection. --- ### 1. Key Technical Specifications The "500-R" suffix typically denotes the current rating and its compliance with environmental standards. | Feature | Specification | | :--- | :--- | | **Current Rating** | 500mA (0.5A) | | **Voltage Rating** | 125V AC / 125V DC | | **Fuse Type** | Slow Blow (Time Lag) | | **Body Material** | Ceramic or Glass Tube (depending on specific sub-series) | | **Termination** | Radial Lead or Surface Mount (Square Body) | | **RoHS Status** | Compliant (-R indicates RoHS compliance) | --- ### 2. Electronic Characteristics #### A. Time-Current Characteristic (Slow Blow) Unlike "Fast Acting" fuses, the MJS 500-R is a **Slow Blow** fuse. - **Purpose:** It is designed to withstand temporary current surges (inrush currents) that occur when a device starts up. - **Function:** It will only blow if the overcurrent persists for a specific duration, preventing "nuisance blowing" caused by motor starts or capacitor charging. #### B. Interrupting Rating (Breaking Capacity) This component is rated to safely interrupt a specific short-circuit current without physically exploding or shattering. For this series, it is typically: - **50A @ 125V AC** - **300A @ 125V DC** #### C. Resistance and Voltage Drop - **Nominal Cold Resistance:** High enough to provide protection, but low enough to minimize power loss during normal operation. - **Voltage Drop:** Measured at 100% of rated current, typically ranging between 100mV to 500mV depending on the specific manufacturing batch. --- ### 3. Physical Construction The MJS series is known for its compact "Micro Fuse" footprint: 1. **Encapsulation:** The internal element is housed in a ceramic body for high heat resistance. 2. **Lead Wires:** Usually made of tin-plated copper for easy soldering onto PCBs. 3. **Marking:** The body is usually laser-marked with "500" to indicate the amperage. --- ### 4. Common Applications Due to its small size and time-lag characteristics, the MJS 500-R is commonly found in: * **Power Supplies:** Protecting the input stage. * **Consumer Electronics:** Chargers, LED drivers, and monitors. * **Industrial Equipment:** Small motors and control circuits. * **Telecom:** Networking hardware protection.