### MF-R055: Electronic Component Overview The **MF-R055** is a Radial Leaded **PPTC (Polymeric Positive Temperature Coefficient)** resettable fuse, commonly referred to as a **Polyswitch**. It is manufactured by **Bourns** and is designed to protect electronic circuits from overcurrent and short-circuit conditions. --- ### Technical Specifications | Parameter | Specification | |:---|:---| | **Hold Current ($I_{hold}$)** | 0.55 Amperes | | **Trip Current ($I_{trip}$)** | 1.10 Amperes | | **Maximum Voltage ($V_{max}$)** | 60 Volts (DC) | | **Maximum Current ($I_{max}$)** | 40 Amperes | | **Power Dissipation ($P_d$)** | 0.70 Watts | | **Operating Temperature** | -40°C to +85°C | | **Lead Spacing** | 5.1 mm | --- ### How It Works Unlike a standard one-time fuse that melts and must be replaced, the MF-R055 is "resettable": 1. **Normal State:** The device has a very low resistance, allowing current to flow normally. 2. **Fault State:** If the current exceeds the trip threshold (1.10A), the internal polymer heats up rapidly. This causes its resistance to increase exponentially, effectively cutting off the current. 3. **Reset State:** Once the power is disconnected and the fault is removed, the device cools down and returns to a low-resistance state. --- ### Key Features and Applications #### Features * **Resettable:** Reduces maintenance costs by eliminating fuse replacement. * **Radial Leaded:** Easy to mount on Through-Hole PCBs. * **Cured Flame Retardant:** Meets UL 94V-0 requirements for safety. * **Agency Recognition:** UL, CSA, and TUV approved. #### Applications * **Power Supplies:** Protection against overload. * **Industrial Controls:** Protecting sensors and control circuits. * **USB Ports:** Shielding computer peripherals from drawing too much power. * **General Electronics:** Used in battery packs and chargers. --- ### Example Circuit Integration To use the MF-R055, it is placed in **series** with the load you wish to protect. ```text [ Power Source (+) ] ---- [ MF-R055 ] ---- [ Load ] ---- [ Power Source (-) ] ```