Based on the part number **47LT-140R-R**, this component is a **Resettable PTC (Positive Temperature Coefficient) Fuse**, specifically from the **47LT Series** (often manufactured by companies like Littelfuse or specialized circuit protection vendors). These components are used for overcurrent protection. Unlike traditional fuses that blow and must be replaced, these "reset" themselves once the fault is cleared and the temperature drops. --- ### Technical Specifications The following table outlines the typical characteristics for the 140R-R variant in this series: | Parameter | Specification | | :--- | :--- | | **Type** | Resettable PTC Fuse (PolySwitch) | | **Hold Current ($I_{hold}$)** | 1.40 Amperes | | **Trip Current ($I_{trip}$)** | 2.80 Amperes | | **Max Voltage ($V_{max}$)** | 15V - 30V (Series dependent) | | **Max Current ($I_{max}$)** | 40A - 100A | | **Mounting Type** | Through-Hole (Radial Lead) | | **Material** | Lead-Free, RoHS Compliant | --- ### How it Works 1. **Normal State:** The device has a very low resistance, allowing current to flow to the circuit normally. 2. **Fault State:** If an overcurrent or short circuit occurs, the internal polymer heats up rapidly. 3. **Tripped State:** The heat causes the polymer to expand into a high-resistance state, effectively "choking" the current flow to a trickle. 4. **Reset:** Once the power is disconnected and the device cools down, the polymer contracts, and the resistance returns to a low level. ### Common Applications * **Battery Packs:** Protecting against short circuits in lithium-ion or NiMH packs. * **Computer Peripherals:** Protecting USB ports and logic circuits. * **Industrial Controls:** Protecting sensors and low-voltage power supplies. * **Automotive:** Low-voltage signal line protection. --- ### Comparison: Standard Fuse vs. PTC Resettable Fuse | Feature | Standard Fuse | PTC (47LT-140R-R) | | :--- | :--- | :--- | | **Reusability** | One-time use | Multiple uses (Resettable) | | **Resistance** | Extremely low | Low (but higher than wire) | | **Reaction Speed** | Very fast | Slower (Thermal based) | | **Maintenance** | Manual replacement | Automatic reset |