The **MF-RHT450** is a specific model of Resettable Fuse (PTC Thermistor) manufactured by **Bourns**. It belongs to the **Multifuse®** family and is specifically designed for high-temperature environments. --- ### 1. Key Technical Specifications The following table outlines the core electrical characteristics of the MF-RHT450: | Parameter | Value | Description | | :--- | :--- | :--- | | **I-hold** | 4.5 Amps | The maximum current the device will hold without tripping at 23°C. | | **I-trip** | 7.8 Amps | The minimum current at which the device will transition to a high-resistance state. | | **V-max** | 16 Volts | The maximum voltage the device can withstand without damage. | | **I-max** | 100 Amps | The maximum fault current the device can safely handle. | | **R-min / R1-max** | 0.022 / 0.054 $\Omega$ | The initial resistance range of the component. | | **Operating Temp** | -40°C to +125°C | Designed for high-heat industrial or automotive environments. | --- ### 2. Functional Characteristics The MF-RHT450 operates on the **PTC (Positive Temperature Coefficient)** principle: * **Normal State:** The device has low resistance, allowing current to flow to the circuit. * **Fault State:** During an overcurrent or overtemperature event, the internal polymer expands, causing resistance to spike dramatically. This "trips" the fuse and limits the current to a safe leakage level. * **Resetting:** Once the fault is removed and the device cools down, the polymer contracts, and the fuse returns to a low-resistance state. --- ### 3. Physical Design and Materials * **Form Factor:** Through-hole (Radial Leaded). * **Material:** High-temperature polymer materials that allow it to operate up to 125°C without nuisance tripping. * **Packaging:** Usually identified by its dark coating (often black or dark grey) with "RHT450" printed on the body. --- ### 4. Common Applications Due to its high hold current and temperature resilience, it is commonly used in: 1. **Automotive Electronics:** Near engine compartments or high-density ECU units. 2. **Industrial Controls:** Motor protection and power supplies operating in hot enclosures. 3. **Battery Packs:** Protecting high-capacity cells during rapid charging/discharging. ---