The **CMS3-9-R** is a high-performance **Common Mode Choke** (Surface Mount Device) manufactured by **Coiltronics** (a brand under **Eaton**). It is part of the CMS series designed for EMI (Electromagnetic Interference) filtering in power and signal applications. --- ## 1. Core Specifications The CMS3-9-R is engineered to provide high impedance at specific frequency ranges to suppress noise while allowing desired signals to pass. | Parameter | Specification (Typical) | | :--- | :--- | | **Inductance** | ~143.0 µH (nominal) | | **DCR (DC Resistance)** | ~0.103 Ω | | **Current Rating ($I_{rms}$)** | ~1.7 Amps | | **Mounting Type** | Surface Mount (SMD) | | **Packaging** | Tape and Reel (indicated by the **-R** suffix) | | **Operating Temperature** | -40°C to +125°C | --- ## 2. Key Features * **Common Mode Suppression:** Specifically designed to reduce common-mode noise in power lines. * **Toroidal Core Design:** Uses a toroidal (ring-shaped) ferrite core which offers high efficiency and low magnetic radiation. * **Dual Windings:** Features two separate windings on a single core, providing balanced filtering for two lines. * **Low Profile:** The "CMS3" size designation refers to its physical footprint, optimized for compact PCB layouts. * **RoHS Compliant:** Lead-free and environmentally friendly. --- ## 3. Pinout and Circuit Representation The device typically has 4 pins. The internal wiring connects two separate coils around the same core. ```text (Line In 1) 1 ●-------● 4 (Line Out 1) ) ( ) ( <-- Magnetic Core ) ( (Line In 2) 2 ●-------● 3 (Line Out 2) ``` --- ## 4. Typical Applications The CMS3-9-R is primarily used in power electronics to ensure regulatory compliance (such as FCC or CE) regarding electromagnetic emissions. 1. **Switch Mode Power Supplies (SMPS):** Filtering input/output noise. 2. **DC-DC Converters:** Preventing high-frequency switching noise from entering the main power bus. 3. **Data Lines:** Protecting sensitive communication lines from environmental interference. 4. **Industrial Controls:** Filtering noise in motor drives or PLC power inputs. ---