## Overview of MF-RHT1300 The **MF-RHT1300** is a high-temperature, radial-leaded Polymeric Positive Temperature Coefficient (**PPTC**) resettable fuse manufactured by Bourns. These components are specifically designed to provide overcurrent protection in harsh environments, particularly automotive and industrial applications. --- ### Key Specifications | Feature | Specification | | :--- | :--- | | **Hold Current ($I_{hold}$)** | 13.0 Amperes | | **Trip Current ($I_{trip}$)** | 26.0 Amperes | | **Maximum Voltage ($V_{max}$)** | 16 Volts | | **Maximum Current ($I_{max}$)** | 100 Amperes | | **Operating Temperature** | -40 °C to +125 °C | | **Packaging Style** | Radial Leaded (Through-hole) | --- ### Operating Principle The MF-RHT1300 functions as a **Resettable Fuse** through the following mechanism: 1. **Normal State:** At standard operating currents, the conductive polymer particles within the device form a low-resistance path, allowing current to flow freely. 2. **Tripped State:** When an overcurrent or short-circuit occurs, the $I^2R$ heating causes the polymer to expand. This expansion breaks the conductive chains, causing the resistance to increase exponentially. 3. **Reset State:** Once the fault is removed and the device cools down, the polymer contracts, the conductive paths reconnect, and the device returns to a low-resistance state. --- ### Critical Electronic Characteristics #### 1. High Temperature Performance Unlike standard PPTCs that are rated for 85 °C, the **RHT series** is engineered for **125 °C**. This makes it suitable for "under-the-hood" automotive electronics where ambient temperatures are significantly higher. #### 2. Thermal Derating The $I_{hold}$ value decreases as the ambient temperature increases. For the MF-RHT1300: * At **23 °C**, it holds 13.0A. * At **125 °C**, the hold current capacity drops significantly (consult the datasheet derating curve for exact values). #### 3. Time to Trip This is the time required for the device to switch to a high-impedance state. For this model, at 5x $I_{hold}$ (65A), the trip time is typically around **18.5 seconds**. --- ### Common Applications * **Automotive:** Protection for motors, wire harnesses, and electronic control units (ECUs). * **Industrial Controls:** Power supplies and protection for heavy machinery sensors. * **Telecommunications:** Protection against power surges in high-heat environments.