### Technical Overview of the Bourns MF-RX014 The **MF-RX014** is a radial-leaded **Polymeric Positive Temperature Coefficient (PPTC)** resettable fuse, part of the MF-RX series manufactured by Bourns. These components are used for overcurrent protection in electronic circuits. --- ### 1. Key Technical Specifications The following table outlines the primary electrical characteristics of the MF-RX014: | Parameter | Value | Description | | :--- | :--- | :--- | | **I-hold** | 0.14 A | Maximum current at which the device will not trip (at 23°C). | | **I-trip** | 0.28 A | Minimum current at which the device will always trip. | | **V-max** | 60 V | Maximum voltage the device can withstand without damage. | | **I-max** | 40 A | Maximum fault current the device can safely interrupt. | | **Pd (typ.)** | 0.40 W | Power dissipated from the device when in tripped state. | | **R-min / R1-max** | 1.50 $\Omega$ / 6.00 $\Omega$ | Resistance range (initial minimum to post-trip maximum). | --- ### 2. How it Works (PPTC Physics) The MF-RX014 operates as a non-linear thermistor: 1. **Normal Operation:** The conductive polymer contains carbon black particles that form paths for current. In this state, resistance is very low. 2. **Overcurrent Event:** Excessive current causes $I^2R$ heating. 3. **Tripping:** Once the temperature reaches a critical threshold (the Curie temperature), the polymer expands, breaking the carbon chains. 4. **High Resistance State:** The resistance increases by several orders of magnitude, limiting the current to a safe leakage level. 5. **Resetting:** Once power is removed and the device cools down, the polymer contracts, the carbon chains reconnect, and the device returns to a low-resistance state. --- ### 3. Physical Dimensions and Construction The "RX" series features a radial leaded package, typically used for Through-Hole Technology (THT) on PCBs. * **Material:** Flame retardant epoxy polymer (UL 94V-0). * **Leads:** Tin-plated copper. * **Marking:** Typically marked with "MF", "RX014", and a date code. --- ### 4. Common Applications Due to its low hold current (140mA) and high voltage rating (60V), the MF-RX014 is ideal for: * **Telecommunications:** Protection for line cards and network equipment. * **Industrial Controls:** Protecting sensors and small motors. * **Power Supplies:** Secondary protection for DC power outputs. * **Computing:** USB port protection and peripheral power rails.