The **RL1220-F-R040F** is a high-precision, low-resistance chip resistor primarily used for current sensing applications. It is manufactured by **Susumu**, a leader in thin-film technology. --- ### 1. Technical Specifications The part number follows a specific nomenclature that defines its physical and electrical characteristics: | Parameter | Specification | Description | | :--- | :--- | :--- | | **Series** | RL1220 | 0805 Imperial size (2.0mm x 1.25mm) | | **Resistance Value** | R040 (40 mΩ) | Very low resistance for current shunt | | **Tolerance** | ±1% (F) | High precision for measurement | | **Power Rating** | 0.33W (1/3 Watt) | Heat dissipation capacity | | **Temperature Coefficient** | 0 ~ +200 ppm/°C | Stability over temperature changes | | **Technology** | Metal Foil / Thin Film | Ensures low noise and high reliability | --- ### 2. Physical Dimensions As an **0805 (Metric 2012)** package, the physical dimensions are as follows: - **Length (L):** 2.00 ± 0.20 mm - **Width (W):** 1.25 ± 0.20 mm - **Thickness (T):** 0.45 ± 0.10 mm --- ### 3. Key Applications Because this component has a very low resistance (40 milliohms), it is not used for standard voltage division but rather for **Current Sensing**: * **Power Management:** Monitoring battery discharge/charge levels in mobile devices. * **DC-DC Converters:** Providing feedback loops for over-current protection. * **Motor Control:** Measuring phase current to ensure smooth operation. * **Automotive Electronics:** Handling small signal monitoring in various ECU modules. --- ### 4. Part Number Breakdown The naming convention for the RL series is structured as follows: ```text RL -> 1220 -> F -> R040 -> F (1) (2) (3) (4) (5) ``` 1. **RL:** Series name (Low resistance chip resistors). 2. **1220:** Case size (2.0 x 1.25mm). 3. **F:** Temperature Coefficient code. 4. **R040:** Resistance value (40 mΩ). 5. **F:** Tolerance (±1.0%).