The **FSMD200-2016-R** is a Surface Mount Device (SMD) Resettable PTC (Positive Temperature Coefficient) thermistor, commonly known as a **PolySwitch** or **Resettable Fuse**. It is designed to protect electronic circuits from overcurrent and over-temperature conditions. --- ### 1. General Specifications The part number follows a specific nomenclature that defines its physical and electrical characteristics. | Parameter | Specification | | :--- | :--- | | **Series** | FSMD (Surface Mount Device) | | **Package Size** | 2016 (Length: 5.0mm, Width: 4.0mm) | | **Hold Current ($I_{hold}$)** | 2.00 Amps | | **Max Voltage ($V_{max}$)** | 8.0 Volts | | **Max Current ($I_{max}$)** | 40 Amps | | **Operating Temperature** | -40°C to +85°C | --- ### 2. How it Works Unlike a traditional fuse that blows once and must be replaced, the FSMD200-2016-R uses a conductive polymer. 1. **Normal Operation:** The device has a very low resistance, allowing current to flow freely. 2. **Fault Condition:** If an overcurrent occurs, the internal temperature rises. 3. **Tripping:** Once the temperature reaches a threshold, the polymer expands, and its resistance increases dramatically (to kilo-ohms), effectively cutting off the current flow. 4. **Reset:** Once the fault is removed and the device cools down, the polymer contracts, and the fuse returns to its low-resistance state. --- ### 3. Key Electrical Behavior | Characteristic | Description | | :--- | :--- | | **$I_{hold}$** | The maximum current the device can carry without tripping. | | **$I_{trip}$** | The minimum current that will cause the device to trip (typically $2 \times I_{hold}$). | | **$P_d$ (Power Dissipation)** | The power dissipated by the device when in its tripped state. | | **Time to Trip** | The speed at which the fuse reacts (e.g., ~2.0 seconds at 8A). | --- ### 4. Typical Applications * **USB Port Protection:** Protecting peripherals and motherboards. * **Battery Packs:** Preventing short circuits in Lithium-ion cells. * **Consumer Electronics:** Game consoles, set-top boxes, and smartphones. * **Industrial Controls:** Protecting low-voltage signal lines. --- ### 5. Land Pattern (Footprint) Example ```c /* Standard 2016 (Imperial) Dimensions in mm */ Length: 4.72 - 5.44 mm Width: 3.70 - 4.43 mm Height: 0.50 - 1.10 mm (Low Profile) ```