The **MF-RHT070-0** is a high-temperature, radial-leaded Polymeric Positive Temperature Coefficient (**PPTC**) resettable fuse manufactured by Bourns. These components are commonly referred to as "resettable fuses" or "polyfuses." --- ### 1. Key Technical Specifications Below are the primary electrical characteristics for the MF-RHT070-0: | Parameter | Specification | Description | | :--- | :--- | :--- | | **$I_{hold}$** | 0.70 Amps | Maximum current the device will hold without tripping. | | **$I_{trip}$** | 1.40 Amps | Minimum current at which the device will transition to high resistance. | | **$V_{max}$** | 16 Volts | Maximum voltage the device can withstand without damage. | | **$I_{max}$** | 40 Amps | Maximum fault current the device can safely interrupt. | | **$P_{d}$** | 1.1 Watts | Power dissipated when the device is in the tripped state. | | **$R_{min} / R_{1max}$** | $0.300 / 0.800 \Omega$ | Resistance range (initial minimum to post-trip maximum). | --- ### 2. Functional Principles The MF-RHT070-0 operates based on the thermal properties of its conductive polymer matrix: * **Normal Operation:** At standard operating currents, the polymer is in a crystalline state, allowing conductive carbon chains to form a low-resistance path. * **Fault Condition:** When an overcurrent or overtemperature event occurs, the $I^2R$ heating causes the polymer to expand and become amorphous. * **Tripping:** This expansion breaks the carbon chains, increasing the resistance exponentially and limiting the current to a safe leakage level. * **Resetting:** Once the fault is removed and the device cools down, the polymer contracts, the conductive paths reform, and the device returns to a low-resistance state. --- ### 3. Distinctive Features * **High Temperature Rating:** Unlike standard PTCs that operate up to 85°C, the "RHT" series is designed for harsh environments, with an operating temperature range of **-40°C to +125°C**. * **Form Factor:** It features a radial-leaded through-hole design with a cured, flame-retardant epoxy polymer insulating material meeting UL 94V-0 requirements. * **Automotive Grade:** This specific series is often AEC-Q200 compliant, making it suitable for automotive under-the-hood applications. --- ### 4. Typical Applications 1. **Automotive Electronics:** Protection for motors, actuators, and electronic control units (ECUs). 2. **Industrial Controls:** Overcurrent protection in high-ambient temperature factory settings. 3. **Power Supplies:** Secondary protection for DC-DC converters and battery chargers.