## Technical Specifications: RL1220-F-R040G The **RL1220-F-R040G** is a high-precision, low-resistance chip resistor manufactured by **Susumu**. It belongs to the RL series, which is specifically designed for current sensing applications due to its excellent stability and low inductance. --- ### 1. Key Technical Parameters | Property | Specification | Details | | :--- | :--- | :--- | | **Resistance Value** | 0.040 $\Omega$ (40m$\Omega$) | Very low resistance for sensing | | **Tolerance** | ±1% (F) | High precision | | **Power Rating** | 1/4 W (0.25W) | Standard power capacity for 0805 size | | **Case Size** | 0805 (Metric 2012) | 2.0mm x 1.25mm footprint | | **Temperature Coefficient** | 0 to +350 ppm/°C (G) | Stability over temperature ranges | | **Technology** | Metal Foil / Thin Film | Ensures low noise and high reliability | --- ### 2. Part Number Breakdown To understand the component better, here is the decoding of the nomenclature: 1. **RL**: Series Code (Current Sensing Chip Resistor). 2. **1220**: Case Size (1.2mm x 2.0mm, equivalent to Imperial 0805). 3. **F**: Resistance Tolerance (±1%). 4. **R040**: Resistance Value ($0.040 \Omega$). The 'R' acts as a decimal point. 5. **G**: Temperature Coefficient of Resistance (TCR) code. --- ### 3. Application Use Cases Because of its low resistance and high accuracy, this part is primarily used in: * **Current Detection:** Measuring the voltage drop across the resistor to determine current flow in a circuit. * **Power Management:** Used in DC-DC converters and battery management systems (BMS). * **Overcurrent Protection:** Helping sensors trigger shut-offs if the current exceeds safe limits. * **Motor Control:** Monitoring feedback loops in small precision motors. --- ### 4. Physical Characteristics * **Form Factor:** Surface Mount Device (SMD). * **Construction:** Features a long-side terminal structure in some variants of this series to improve heat dissipation and reduce parasitic inductance. * **Durability:** Designed to withstand harsh environments with high sulfur resistance (typical of the Susumu RL series).