The **FSMD150-2920-R** is a surface-mount 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. Technical Specifications The following table highlights the primary electrical characteristics of the FSMD150-2920-R: | Parameter | Value | Description | | :--- | :--- | :--- | | **Hold Current ($I_{hold}$)** | 1.50 A | Max current the device will pass without tripping. | | **Trip Current ($I_{trip}$)** | 3.00 A | Min current at which the device will switch to high resistance. | | **Max Voltage ($V_{max}$)** | 33 V | Maximum voltage the device can withstand. | | **Max Current ($I_{max}$)** | 100 A | Maximum fault current the device can safely handle. | | **Power Dissipation ($P_d$)** | 1.5 W | Power dissipated when the device is in a tripped state. | | **Form Factor** | 2920 | Surface mount package (approx. 7.5 x 5.1 mm). | --- ## 2. Key Features and Operation The device functions as a solid-state fuse that "resets" itself once the fault is cleared and the temperature drops. ### How it Works: 1. **Normal State:** The device has a very low resistance, allowing current to flow to the load. 2. **Fault State:** During an overcurrent event, the internal polymer heats up. Once it reaches a critical temperature, it expands, causing the internal conductive particles to disconnect. 3. **High Resistance:** The resistance increases dramatically, limiting the current to a safe leakage level. 4. **Reset:** Once the power is removed or the fault is fixed, the device cools down, the polymer contracts, and the conductive paths are restored. ### Advantages: * **Resettable:** Eliminates the need for physical fuse replacement. * **Small Footprint:** The 2920 SMD package is ideal for high-density PCB designs. * **Reliability:** Provides consistent protection against short circuits and power surges. --- ## 3. Typical Applications The FSMD150-2920-R is widely used in various electronic sectors: * **Computer Peripherals:** USB ports, IEEE 1394 (FireWire) ports. * **Consumer Electronics:** Game consoles, digital cameras, and mobile phones. * **Automotive:** Protection for small motors and interior lighting circuits. * **Telecommunications:** Network interface cards and modems. ---