The **FP1208R1-R21-R** is a high-current, shielded drum core power inductor manufactured by **Eaton (formerly Cooper Bussmann/Coiltronics)**. It is part of the FP1208 series, specifically designed for high-frequency voltage regulator modules (VRMs). ### 1. Key Technical Specifications | Parameter | Value | | :--- | :--- | | **Inductance** | 210 nH (0.21 µH) | | **Tolerance** | ±10% | | **DC Resistance (DCR)** | 0.28 mΩ (Max) | | **Saturation Current ($I_{sat}$)** | 67 A | | **RMS Current ($I_{rms}$)** | 54 A | | **Operating Temperature** | -40°C to +125°C | | **Package / Case** | 12.1mm x 8.0mm x 8.0mm | --- ### 2. Physical Construction The "FP" prefix stands for **Flat-Pac**. This series uses a unique construction method: * **Core Material:** Ferrite core which offers low core loss at high switching frequencies. * **Shielding:** It is a magnetically shielded structure, which minimizes Electromagnetic Interference (EMI) with surrounding components. * **Winding:** It features a flat-wire design. This reduces the "Proximity Effect" and "Skin Effect," allowing it to handle extremely high currents with minimal heat generation (low DCR). --- ### 3. Part Number Breakdown The nomenclature follows a specific logic: | Segment | Meaning | | :--- | :--- | | **FP1208** | Product Series and Dimensions (approx. 12x8mm footprint) | | **R1** | Revision or Internal design version | | **-R21** | Inductance value (R21 = 0.21 µH) | | **-R** | RoHS compliant / Lead-free | --- ### 4. Typical Applications Because of its high saturation current and low DCR, this inductor is commonly used in: * **Multi-phase buck regulators:** Powering CPUs, GPUs, and ASICs. * **Voltage Regulator Modules (VRM):** Specifically for Servers and Networking equipment. * **Desktop and Workstations:** High-end power delivery circuits. * **DC-DC Converters:** Point-of-Load (POL) modules where space is tight but power requirements are high. --- ### 5. Benefits * **High Efficiency:** The extremely low DCR (0.28 mΩ) minimizes power loss in the form of heat. * **Stability:** Ferrite material provides a very "soft" saturation curve, ensuring the inductance doesn't drop off abruptly under heavy load. * **Small Footprint:** Provides one of the highest current-to-size ratios in the industry.