The **440LD39-R** is a specific type of ceramic disc capacitor, primarily designed for suppression and safety applications. It is part of the **Vishay Cera-Mite 440L Series**. --- ## 1. Component Overview This component is classified as a **Safety Certified AC Capacitor**. These are used in "Line-to-Ground" applications (Y-Class) where failure could lead to an electric shock risk. ### Technical Specifications | Parameter | Specification | | :--- | :--- | | **Manufacturer** | Vishay Cera-Mite | | **Series** | 440L (Y1 Safety Rated) | | **Capacitance Value** | 3900 pF (0.0039 µF) | | **Tolerance** | ±20% | | **Voltage Rating** | 500 VAC (RMS) | | **Dielectric Material** | Ceramic (Class 2) | | **Safety Class** | Y1 (Line-to-Ground) | | **Temperature Range** | -30°C to +125°C | --- ## 2. Key Features * **Safety Certification:** Certified by international bodies (UL, CSA, VDE) for safety-critical circuits. * **Self-Healing:** Designed to withstand high voltage impulses without short-circuiting. * **Flame Retardant:** Encapsulated in a flame-retardant epoxy resin (UL 94 V-0). * **High Voltage Insulation:** Designed to handle transient voltages (surges) up to 8kV. --- ## 3. Part Number Breakdown: 440LD39-R Understanding the nomenclature helps in identifying equivalent parts: * **440L:** The series designation (Y1 safety rated, 500VAC). * **D:** Diameter code/Dielectric characteristics. * **39:** The significant figures for capacitance (3900 pF). * **-R:** Indicates compliance with **RoHS** (Reduction of Hazardous Substances) standards. --- ## 4. Common Applications These parts are almost exclusively found in the input stage of power supplies: 1. **EMI/RFI Filtering:** Reducing electromagnetic interference from the power line. 2. **AC Line Filtering:** Used in Switch Mode Power Supplies (SMPS). 3. **Antenna Coupling:** Providing isolation between the mains and the internal circuitry. 4. **Grounding:** Safely shunting high-frequency noise to the chassis/ground. ---