## MF-RHT900 Overview The **MF-RHT900** is a specific model of a **Polymeric Positive Temperature Coefficient (PPTC)** resettable fuse, manufactured by Bourns. It is part of the MF-RHT series, which is specifically designed for high-temperature environments, such as automotive applications. --- ### Technical Specifications The following table summarizes the key electrical characteristics of the MF-RHT900: | Parameter | Specification | Description | | :--- | :--- | :--- | | **Hold Current ($I_{hold}$)** | 9.0 A | The maximum current the device will pass without tripping at 23°C. | | **Trip Current ($I_{trip}$)** | 16.5 A | The minimum current at which the device will transition to a high-resistance state. | | **Max Voltage ($V_{max}$)** | 16 V | The maximum voltage the device can withstand without damage. | | **Max Current ($I_{max}$)** | 100 A | The maximum fault current the device can safely interrupt. | | **Operating Temp Range** | -40°C to +125°C | Designed for high-ambient temperature environments. | | **Mounting Type** | Radial Leaded | Through-hole mounting for PCBs. | --- ### How it Works The MF-RHT900 functions as a **non-linear thermistor**: 1. **Normal State:** Under normal current levels, the conductive particles within the polymer matrix form low-resistance paths, allowing current to flow easily. 2. **Fault State:** If an overcurrent or over-temperature event occurs, the polymer heats up and expands. This expansion breaks the conductive paths. 3. **Tripped State:** The device's resistance increases sharply (by several orders of magnitude), limiting the current to a safe leakage level. 4. **Reset:** Once the fault is cleared and the device cools down, the polymer contracts, the conductive paths re-establish, and the fuse resets itself. --- ### Key Features and Applications #### Features * **High Temperature Rating:** Unlike standard PTCs that trip early in hot environments, the RHT series maintains its hold current better at elevated temperatures. * **Resettable:** Eliminates the need for manual fuse replacement after a surge. * **Agency Recognition:** Typically AEC-Q200 compliant (Automotive Grade). #### Common Applications * **Automotive Electronics:** Protection for motors, actuators, and electronic control units (ECUs). * **Industrial Controls:** Overcurrent protection in high-heat manufacturing environments. * **Battery Packs:** Protecting cells from discharge surges. ---