The **TMR3JB5L00** is a high-precision, low-resistance shunt resistor manufactured by **KOA Speer Electronics**. It is specifically designed for current sensing applications in power electronics. --- ### 1. Key Technical Specifications | Parameter | Specification | |:---|:---| | **Resistance Value** | 5 mΩ (0.005 Ω) | | **Power Rating** | 3 Watts | | **Tolerance** | ±5% (denoted by 'J' in the part number) | | **Temperature Coefficient (TCR)** | ±150 ppm/°C | | **Operating Temperature** | -55°C to +155°C | | **Case Style** | Molded SMD (Surface Mount Device) | --- ### 2. Physical and Structural Parts The TMR series features a unique construction to handle high power in a small footprint: * **Resistive Element:** Utilizes a metal plate or alloy with high stability to ensure the resistance remains constant even under thermal stress. * **Molded Encapsulation:** The internal metal element is protected by a flame-retardant epoxy resin. This provides superior mechanical strength and environmental protection compared to standard thick-film resistors. * **Terminations:** Features large metal end-caps designed for high solderability and effective heat dissipation into the PCB (Printed Circuit Board) copper traces. --- ### 3. Functional Features * **Low Inductance:** Because the internal element is a solid metal plate rather than a coil, it has extremely low parasitic inductance. This is critical for high-frequency switching circuits. * **High Power-to-Size Ratio:** The 3W rating is significantly higher than standard resistors of a similar size, achieved through optimized thermal management. * **Current Sensing:** It works on Ohm's Law ($V = I \times R$). By measuring the tiny voltage drop across the 5mΩ resistance, the system controller can calculate the exact current flowing through the circuit. --- ### 4. Typical Applications The TMR3JB5L00 is commonly found in circuits where monitoring high current is essential for safety or control: 1. **DC-DC Converters:** Monitoring output current for load regulation. 2. **Battery Management Systems (BMS):** Tracking charge and discharge cycles in lithium-ion packs. 3. **Motor Controllers:** Sensing phase current to protect against overcurrent conditions. 4. **Automotive Electronics:** Used in electronic power steering or lighting control modules. ---