The **MF-R075** is a specific model of a **Polymeric Positive Temperature Coefficient (PPTC)** resettable fuse, manufactured primarily by Bourns. These components are used for circuit protection against overcurrent conditions. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Hold Current ($I_{hold}$)** | 0.75 Amps | | **Trip Current ($I_{trip}$)** | 1.50 Amps | | **Maximum Voltage ($V_{max}$)** | 60V | | **Maximum Current ($I_{max}$)** | 40 Amps | | **Power Dissipation ($P_d$)** | 0.9 Watts | | **Mounting Type** | Through-hole (Radial Leaded) | --- ### 2. How it Works The MF-R075 acts like a "smart fuse." Unlike a traditional glass fuse that blows and must be replaced, the PPTC "resets" itself once the fault is cleared and the temperature drops. 1. **Normal State:** The device has a low resistance, allowing current to flow to the circuit. 2. **Fault State (Overcurrent):** High current causes internal heating. The polymer matrix expands, breaking the conductive paths and increasing resistance drastically (tripping). 3. **Reset State:** Once power is removed and the device cools down, the polymer contracts, restoring conductive paths and low resistance. --- ### 3. Physical Characteristics * **Encapsulation:** Cured, flame-retardant epoxy polymer (meets UL 94V-0). * **Lead Material:** Tin-plated copper. * **Marking:** Usually marked with "B" (Bourns Logo), "R075", and a date code. --- ### 4. Common Applications * **Computer Peripherals:** USB ports and plug-and-play interfaces. * **Industrial Controls:** Protection for sensors and actuators. * **General Electronics:** Protection against short circuits in power supplies and battery packs. * **Telecommunications:** Protection for line cards and modems. --- ### 5. Part Number Breakdown ```text MF - R 075 | | | | | +-- Hold Current (0.75 Amps) | +----- Radial Leaded (Package Style) +---------- Multifuse® (Bourns Brand Name) ```