The **MF-R015/600-B** is a specific model of Polymer Positive Temperature Coefficient (**PPTC**) resettable fuse, manufactured by Bourns. It is designed specifically for circuit protection against overcurrent and short-circuit conditions. --- ## 1. Core Technical Specifications | Parameter | Specification | Description | | :--- | :--- | :--- | | **Hold Current ($I_{hold}$)** | 0.150 A (150mA) | The maximum current the device can carry without tripping. | | **Trip Current ($I_{trip}$)** | 0.300 A (300mA) | The minimum current at which the device will switch to high resistance. | | **Max Voltage ($V_{max}$)** | 600 V | The maximum voltage the device can withstand. | | **Max Interrupt Current** | 3 A | The maximum fault current the fuse can safely handle. | | **Packaging Style** | Radial Leaded | Through-hole mounting (Thru-hole). | | **Typical Power** | 1.0 W | Power dissipated when the device is in a tripped state. | --- ## 2. Functionality and Mechanism ### How it Works The MF-R015/600-B acts as a "resettable" fuse. It uses a conductive polymer composite: 1. **Normal State:** Under normal current levels, the polymer is in a crystalline state, and conductive particles form a low-resistance path. 2. **Tripped State:** When an overcurrent occurs, $I^2R$ heating causes the polymer to expand and become amorphous. This breaks the conductive paths, increasing the resistance exponentially and dropping the current to a trickle. 3. **Resetting:** Once the fault is removed and the power is cycled (allowing the device to cool), the polymer shrinks back to its original state, and the device becomes conductive again. ### Key Advantages * **Maintenance Free:** Unlike standard glass fuses, it does not need to be replaced after a single fault event. * **High Voltage Rating:** The "600" in the part number indicates a 600V rating, making it suitable for AC line applications and telecommunications. --- ## 3. Applications and Use Cases The MF-R015/600-B is frequently used in high-voltage environments where space is limited but protection is critical: * **Telecommunications:** Protection for Tip and Ring lines in PSTN equipment against power cross and lightning surges. * **Customer Premise Equipment (CPE):** Modems, set-top boxes, and internet gateways. * **Industrial Controls:** Protecting sensors and control circuits from wiring errors. * **Power Supplies:** Secondary side protection for transformers. --- ## 4. Part Number Breakdown | Segment | Meaning | | :--- | :--- | | **MF-R** | Multifuse® Resettable Fuse - Radial Leaded Series | | **015** | Hold Current (0.15 Amps) | | **600** | Maximum Voltage (600 Volts) | | **-B** | Bulk Packaging (Standard lead form) |