The **SD25-681-R** is a member of the SD series of shielded drum core inductors, primarily manufactured by **Eaton (formerly Cooper Bussmann/Coiltronics)**. These components are designed for high-density applications where electromagnetic interference (EMI) shielding and power efficiency are critical. --- ### 1. Key Specifications Below are the technical parameters for the **SD25-681-R**: | Parameter | Value | | :--- | :--- | | **Inductance** | 680 µH (Microhenries) | | **Tolerance** | ±20% | | **DC Resistance (DCR)** | ~1.62 Ω (Typical) | | **Saturation Current ($I_{sat}$)** | 0.283 A (Amps) | | **RMS Current ($I_{rms}$)** | 0.407 A (Amps) | | **Package / Case** | SD25 (7.2mm x 7.2mm x 2.5mm) | | **Shielding** | Magnetically Shielded | --- ### 2. Physical Construction The part is built using specific materials to balance size and performance: * **Core Material:** Ferrite drum core. * **Shielding:** A ferrite sleeve surrounds the winding, which minimizes the magnetic field leakage, preventing the inductor from interfering with nearby sensitive components on the PCB. * **Mounting:** Surface Mount Device (SMD). * **RoHS Compliance:** The "-R" suffix indicates that the part is fully compliant with RoHS (Restriction of Hazardous Substances) standards. --- ### 3. Electronic Behavior & Function The SD25-681-R serves several critical roles in an electronic circuit: #### A. Energy Storage In DC-DC converters (Buck or Boost), this inductor stores energy in its magnetic field during the "ON" cycle of a switch and releases it during the "OFF" cycle to maintain a steady output voltage. #### B. Noise Filtering (Low-Pass Filter) Due to its high inductance (680 µH), it is highly effective at blocking high-frequency AC noise while allowing DC current to pass. It is often used in power supply lines to smooth out ripples. #### C. High Saturation Characteristics The "SD" series is known for a "soft" saturation curve. This means the inductance drops gradually as the current increases, rather than dropping off suddenly, which provides a safety margin in over-current situations. --- ### 4. Typical Applications * **Consumer Electronics:** Digital cameras, media players, and handheld GPS units. * **Computing:** DC-DC converters for motherboards and servers. * **Battery Powered Devices:** Ideal for small devices due to the low-profile 2.5mm height. * **LED Drivers:** Providing constant current for lighting applications.