The **ULR3-R001FT2** is a high-precision, high-power **Current Sense Resistor** manufactured by Welwyn (a TT Electronics brand). This component is specifically designed for monitoring current levels by measuring the voltage drop across its low-resistance element. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Resistance Value** | 0.001 Ohms (1 mΩ) | | **Power Rating** | 3 Watts | | **Tolerance** | ±1% (indicated by 'F') | | **Package / Case** | 2512 (SMD - Surface Mount Device) | | **Temperature Coefficient** | ±100 ppm/°C | | **Technology** | Metal Element / Metal Alloy | --- ### 2. Part Number Breakdown Understanding the nomenclature helps in identifying its characteristics: * **ULR:** Series Name (Ultra-Low Resistance). * **3:** Power Rating (3 Watts). * **R001:** Resistance value (R001 = 0.001 $\Omega$). * **F:** Tolerance Code (F = ±1%). * **T2:** Packaging (Typically refers to Tape and Reel). --- ### 3. Core Features & Benefits * **Low Inductance:** Because it uses a solid metal alloy element rather than a wire-wound structure, it has extremely low inductance, making it suitable for high-frequency switching applications. * **High Power Density:** Delivering 3W in a 2512 package is considered high performance, requiring effective thermal management on the PCB. * **Thermal Stability:** The metal alloy construction ensures that the resistance value remains stable even as the component heats up during operation. * **AEC-Q200 Qualified:** These parts are often tested to automotive standards, ensuring high reliability in harsh environments. --- ### 4. Typical Applications The ULR3-R001FT2 is commonly found in circuits where power management and current monitoring are critical: 1. **Battery Management Systems (BMS):** Monitoring charging and discharging currents in Li-ion battery packs. 2. **DC-DC Converters:** Providing feedback loops for regulated power supplies. 3. **Motor Control:** Detecting "over-current" conditions to protect motors and drivers. 4. **Power Inverters:** Used in solar or automotive inverters to sense output current. --- ### 5. Layout Considerations When using a **1 mΩ** resistor, the resistance of the PCB copper traces can interfere with the reading. Designers should use a **Kelvin Connection (4-terminal sensing)** layout style: * Two pads carry the high current. * Two separate "sense" traces are connected directly to the resistor pads to measure the voltage drop without including the voltage drop of the power traces. ---