## Technical Overview: 3JS40-R The **3JS40-R** is a specific model of a **Miniature Fast-Acting Surface Mount Fuse** manufactured by Bel Fuse Inc. It is part of the **3JS** series, designed to provide overcurrent protection in space-constrained electronic circuits. --- ### 1. Key Technical Specifications The following table outlines the primary electronic characteristics of the 3JS40-R: | Parameter | Value / Specification | | :--- | :--- | | **Current Rating** | 400mA (0.4A) | | **Voltage Rating (AC/DC)** | 350V AC / 140V DC | | **Fuse Type** | Fast-Acting (Quick Acting) | | **Mounting Type** | Surface Mount (SMD / SMT) | | **Body Material** | Ceramic Tube with Gold-Plated Brass Caps | | **Interrupting Rating** | 100A @ 350V AC | | **Operating Temperature** | -55°C to +125°C | | **RoHS Compliant** | Yes (Suffix -R indicates RoHS compliance) | --- ### 2. Physical Characteristics The "3JS" series is known for its compact, brick-like form factor. * **Size:** Standard 2.6mm x 7.1mm footprint (approximate). * **Termination:** Square end caps designed for automated pick-and-place surface mount assembly. * **Marking:** The body is typically marked with the current rating (e.g., "400") for identification. --- ### 3. Application and Usage Because the 3JS40-R is a **Fast-Acting** fuse, it is engineered to blow quickly when an overcurrent condition occurs. It does not tolerate high "in-rush" currents like a Time-Delay (Slow-Blow) fuse would. **Common Applications:** * **Telecommunications:** Protection for line cards and networking equipment. * **Power Supplies:** Secondary side protection for AC/DC converters. * **Consumer Electronics:** Protection for LED drivers and battery chargers. * **Industrial:** PC board level protection for sensors and controllers. --- ### 4. Part Number Breakdown: 3JS40-R Understanding the nomenclature helps in identifying variants: * **3JS:** The series name (Fast-acting ceramic tube SMD). * **40:** Indicates the current rating (400mA). * **-R:** Indicates compliance with **RoHS** (Restriction of Hazardous Substances) standards. ---