The **MF-R075** is a specific model of a Resettable Fuse, part of the **Multifuse®** series manufactured by Bourns. These components are technically known as **PPTCs** (Polymer Positive Temperature Coefficient) devices. --- ## 1. Core Technical Specifications The "075" in the part number indicates the holding current of the device. Below are the primary electrical characteristics for the MF-R075: | Parameter | Value | Description | | :--- | :--- | :--- | | **$I_{hold}$** | 0.75 A | The maximum current the device will pass without tripping at 23°C. | | **$I_{trip}$** | 1.50 A | The minimum current at which the device will switch to a high-resistance state. | | **$V_{max}$** | 60 V | The maximum voltage the device can withstand without damage. | | **$I_{max}$** | 40 A | The maximum fault current the device can safely interrupt. | | **$P_d$** | 0.9 W | Power dissipated when the device is in the tripped state. | | **$R_{min}$** | 0.18 $\Omega$ | Minimum resistance before tripping. | --- ## 2. How it Functions Unlike a traditional fuse that melts and must be replaced, the MF-R075 acts like a "self-healing" circuit breaker. 1. **Normal State:** The polymer contains conductive particles (carbon black) that form a path for current. Resistance is very low. 2. **Fault State (Overcurrent):** When current exceeds $I_{trip}$, the polymer heats up and expands. This breaks the conductive chains. 3. **Tripped State:** The resistance increases exponentially, limiting the current to a safe leakage level. 4. **Reset State:** Once the power is removed and the fault is cleared, the device cools down, the polymer contracts, and the conductive paths are restored. --- ## 3. Physical & Environmental Attributes * **Packaging:** Radial leaded (Through-hole). * **Material:** Cured flame-retardant epoxy polymer (meeting UL 94V-0). * **Operating Temperature:** -40°C to +85°C. * *Note: PPTCs are thermally sensitive. If the ambient temperature is high, the fuse will trip at a lower current than 0.75A.* --- ## 4. Common Applications The MF-R075 is typically used in low-voltage electronics where space is available for through-hole components: * **USB Port Protection:** Protecting against shorts in peripheral devices. * **Power Supplies:** Secondary protection for transformers or DC-DC converters. * **Industrial Controls:** Protecting sensors and PLC I/O ports. * **Security Systems:** Overload protection for cameras and alarm sensors.