The **MF-RHT series** (specifically parts like the MF-RHT016 or MF-RHT160) refers to a line of **High-Temperature Radial Leaded Polymer Positive Temperature Coefficient (PPTC)** resettable fuses manufactured by **Bourns**. These components are used for overcurrent protection, designed to "trip" and limit current during a fault and reset once the power is removed and the fault is cleared. --- ### 1. Key Technical Specifications The "16" in the part number usually refers to the **Hold Current ($I_{hold}$)**, representing the maximum current the device can carry without tripping. Depending on the specific suffix, this could be **0.16A** or **1.6A**. | Feature | Specification (Typical for MF-RHT Series) | | :--- | :--- | | **Technology** | Polymeric PTC (Resettable Fuse) | | **Max Voltage ($V_{max}$)** | 16V to 30V (varies by specific model) | | **Max Current ($I_{max}$)** | Up to 100A (fault current capacity) | | **Operating Temp Range** | -40 °C to +125 °C | | **Hold Current ($I_{hold}$)** | The current at which the device will not trip | | **Trip Current ($I_{trip}$)** | The current at which the device is guaranteed to trip | --- ### 2. Physical Characteristics and Construction The MF-RHT series is designed for through-hole mounting on PCBs. * **Materials:** Composed of a conductive plastic matrix (carbon black mixed with a polymer). * **Form Factor:** Radial leaded (two wires extending from the bottom of a teardrop-shaped or rectangular coated body). * **High-Temperature Rating:** The "HT" designation signifies its suitability for automotive or industrial environments where ambient temperatures are high. --- ### 3. How It Works (The PTC Effect) 1. **Normal State:** The polymer is in a crystalline state, and carbon particles form conductive paths. Resistance is very low. 2. **Fault State (Overcurrent):** Excessive current causes $I^2R$ heating. The polymer expands and becomes amorphous. 3. **Tripped State:** The expansion breaks the carbon chains, causing the resistance to skyrocket, effectively "opening" the circuit. 4. **Reset:** Once the fault is removed and the device cools, the polymer shrinks, re-establishing the conductive paths. --- ### 4. Applications Because of the **High-Temperature (HT)** rating, these parts are commonly found in: * **Automotive Electronics:** Near engines or in cabin electronics subject to solar heating. * **Industrial Controls:** Motor protection and power supplies. * **Battery Packs:** Protection against short circuits during charging or discharging. ---