## Technical Overview: CMS1-2-R Common Mode Choke The **CMS1-2-R** is a surface-mount common mode inductor (choke) manufactured by **Eaton (formerly Bussmann/Coiltronics)**. It is part of the CMS series, designed primarily for noise suppression in power and signal lines. --- ### 1. Key Technical Specifications Below are the primary electrical and physical characteristics of the CMS1-2-R: | Parameter | Specification | | :--- | :--- | | **Inductance (Typical)** | 215 µH | | **Rated Current (Irms)** | 1.1 Amps | | **DC Resistance (DCR)** | 0.160 Ω (Maximum per winding) | | **Voltage Rating** | 160 Vdc | | **Isolation Voltage** | 300 Vdc | | **Package Type** | Surface Mount (SMD) - Size 1 | | **Operating Temperature** | -40°C to +125°C | --- ### 2. Physical Design and Construction The device consists of two identical windings wound on a single ferrite core. * **Core Material:** Ferrite construction provides high impedance at high frequencies to effectively filter electromagnetic interference (EMI). * **Form Factor:** It uses a "Size 1" footprint, which is compact for high-density PCB layouts. * **Termination:** Lead-free, RoHS compliant construction with tin-plated terminals. --- ### 3. Functional Applications The CMS1-2-R is used to filter **Common Mode Noise**—noise that flows in the same direction on both signal lines—while allowing the desired differential signal to pass with minimal attenuation. #### Common Use Cases: 1. **Switch Mode Power Supplies (SMPS):** Filtering input and output stages to meet EMI compliance. 2. **DC-DC Converters:** Reducing ripple and high-frequency switching noise. 3. **Data Lines:** Protecting sensitive communication lines from environmental electrical noise. 4. **CAN Bus / Industrial Interfaces:** Ensuring signal integrity in noisy industrial environments. --- ### 4. Circuit Representation In a schematic, the CMS1-2-R is represented as two coupled inductors with polarity dots indicating the winding direction. ```text Line In (+) ----( L1 )---- Line Out (+) :: Line In (-) ----( L2 )---- Line Out (-) (Common Ferrite Core) ``` ---