### Overview of MF-RHT650 The **MF-RHT650** is a specific model of Polymer Positive Temperature Coefficient (**PPTC**) resettable fuse, manufactured by Bourns. It is part of the MF-RHT series, which is specifically designed for high-temperature applications, such as those found in automotive environments. --- ### Technical Specifications The following table outlines the primary electrical characteristics of the MF-RHT650: | Parameter | Specification | Description | | :--- | :--- | :--- | | **$I_{hold}$** | 6.5 Amps | The maximum current the device will pass without tripping at 23°C. | | **$I_{trip}$** | 13.7 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 interrupt. | | **$R_{min}$** | 0.009 Ohms | Minimum resistance in the off state (before tripping). | | **Operating Temp** | -40°C to +125°C | Designed for extreme thermal environments. | --- ### Key Electronic Features #### 1. Resettable Protection Unlike traditional glass or ceramic fuses that "blow" and must be replaced, the MF-RHT650 is **resettable**. When a fault (overcurrent) occurs, the internal polymer heats up and expands, increasing resistance drastically and cutting the current. Once the fault is removed and the device cools down, it returns to a low-resistance state. #### 2. High-Temperature Material The "HT" in the part number stands for **High Temperature**. While standard PTCs might trip prematurely at 85°C, this unit is engineered to maintain its hold current even in engine compartments or industrial machinery where ambient temperatures reach 125°C. #### 3. Through-Hole Package The MF-RHT650 is a **radial-leaded** component. This makes it suitable for: * Standard PCB through-hole mounting. * Environments with high vibration (where surface mount parts might crack). --- ### Typical Applications * **Automotive:** Protection for motor circuits, wire harnesses, and electronic control units (ECUs). * **Industrial:** Protection for power supplies and controllers operating near heat sources. * **Agricultural Equipment:** Protection for heavy-duty outdoor electronics. --- ### Circuit Symbol and Usage In a schematic, it is represented as a resistor with a diagonal line or a specific PTC symbol. ```text F1 (MF-RHT650) -----[ PTC ]----- ```