## MF-R017: Technical Overview The **MF-R017** is a specific model of a **Polymeric Positive Temperature Coefficient (PPTC)** resettable fuse, manufactured by Bourns. It is part of the MF-R series, commonly used for overcurrent protection in electronic circuits. ### 1. Key Specifications The following table highlights the critical electrical characteristics of the MF-R017: | Parameter | Specification | Description | | :--- | :--- | :--- | | **I-hold** | 0.17 Amps | Maximum current the device will pass without tripping. | | **I-trip** | 0.34 Amps | Minimum current at which the device will switch to high resistance. | | **V-max** | 60 Volts | Maximum voltage the device can withstand without damage. | | **I-max** | 40 Amps | Maximum fault current the device can safely interrupt. | | **Pd-typ** | 0.48 Watts | Typical power dissipated when in the tripped state. | | **R-min / R-max** | 3.30 / 5.21 $\Omega$ | Resistance range of the device at $23^\circ C$ before tripping. | --- ### 2. How it Works Unlike traditional fuses that "blow" and must be replaced, the MF-R017 is **resettable**. 1. **Normal State:** The conductive polymer allows current to flow with low resistance. 2. **Fault State:** If an overcurrent occurs, internal $I^2R$ heating causes the polymer to expand. This breaks the conductive paths, increasing resistance dramatically and limiting current to a safe level. 3. **Reset State:** Once the power is removed and the fault is cleared, the device cools down, the polymer contracts, and it returns to a low-resistance state. --- ### 3. Physical Attributes The MF-R017 belongs to the **Radial Leaded** category, meaning it is designed for through-hole mounting on PCBs. * **Material:** Cured, flame-retardant epoxy polymer (meeting UL 94V-0). * **Lead Material:** Tin-plated copper. * **Marking:** Usually identified by the code "R017" on the body of the yellow/brown disk. --- ### 4. Typical Applications The MF-R017 is ideal for low-current applications requiring protection against short circuits or power surges: * **Telecommunications:** Protection for line cards and modems. * **Consumer Electronics:** Power supplies and battery chargers. * **Industrial Controls:** Sensor protection and PLC I/O ports. * **Computers:** USB port protection and peripheral interfaces.