The **FSMD110-16-R** is a specific model of a **Surface Mount Resettable PTC (Positive Temperature Coefficient) Fuse**, commonly referred to as a **PolySwitch**. It is manufactured by companies like **Formosa MS** and is designed to protect electronic circuits from overcurrent and over-temperature conditions. --- ### 1. Technical Specifications The following table highlights the primary electrical characteristics of the FSMD110-16-R: | Parameter | Value | Description | | :--- | :--- | :--- | | **Hold Current ($I_{hold}$)** | 1.10 A | Maximum current the device will pass without tripping. | | **Trip Current ($I_{trip}$)** | 2.20 A | Minimum current at which the device will switch to high resistance. | | **Maximum Voltage ($V_{max}$)** | 16 V | Maximum voltage the device can withstand without damage. | | **Maximum Current ($I_{max}$)** | 100 A | Maximum fault current the device can safely interrupt. | | **Power Dissipation ($P_d$)** | 0.8 W | Typical power dissipated when the device is in a tripped state. | | **Package Size** | 1812 (Imperial) | Surface mount dimensions (approx. 4.5 x 3.2 mm). | --- ### 2. How It Works Unlike a traditional one-time fuse that blows and must be replaced, the FSMD110-16-R is **resettable**. 1. **Normal Operation:** The device has a very low resistance, allowing current to flow to the load. 2. **Fault Condition:** If an overcurrent occurs, the internal temperature of the PTC material rises. 3. **Tripping:** Once the temperature reaches a critical threshold, the polymer structure expands, causing the resistance to increase exponentially. This limits the current to a safe, leakage level. 4. **Resetting:** Once the fault is removed and the device cools down, the polymer contracts, and the resistance returns to a low state. --- ### 3. Key Features & Applications #### Features * **Surface Mount Design:** Small footprint (1812) ideal for high-density PCB layouts. * **Fast Time-to-Trip:** Protects sensitive electronics quickly. * **Lead-Free/RoHS Compliant:** Environmentally friendly and suitable for modern manufacturing. #### Common Applications * **USB Port Protection:** Safeguarding ports against short circuits from peripheral devices. * **Motherboards & Peripherals:** General overcurrent protection for logic circuits. * **Battery Packs:** Preventing excessive discharge or charging currents. * **Automotive Electronics:** Protection for small motors and sensors. --- ### 4. Typical Marking and Packaging * **Marking:** Usually labeled with "110" on the top of the component to indicate the 1.1A hold current. * **Material:** The "-R" suffix typically denotes RoHS compliance and "Tape & Reel" packaging for automated assembly.