TDK EP21 Flat-Wire Common-Mode Chokes

Introduction

TDK EP21 flat-wire common-mode chokes are compact surface-mount magnetic components designed to reduce electromagnetic interference (EMI) in high-current power circuits. They are particularly suited to DC-DC converter input and output filtering, as well as low-voltage EMC protection designs.

Part Description

The EP21 series consists of double common-mode chokes built with flat-wire windings and underbody terminations for efficient use of board space. Their construction supports high-current operation while maintaining low DC resistance, helping reduce power loss in demanding power-delivery paths.

Key characteristics include:

• Surface-mount common-mode choke construction
• Flat-wire winding technology
• High rated current capability from 20.3A to 35A
• Nominal inductance options from 160µH to 640µH
• Low DC resistance for improved efficiency
• Compact package with underbody terminals
• Designed for EMI filtering and EMC noise suppression
• Suitable for DC-DC converter and low-voltage protection circuits

By attenuating common-mode noise, these chokes can help products meet electromagnetic compatibility requirements and improve the reliability of nearby sensitive electronics.

Applications

Potential applications for TDK EP21 common-mode chokes include:

• DC-DC converter input filters
• DC-DC converter output filters
• Point-of-load power supplies
• High-current low-voltage power rails
• EMI suppression networks
• EMC protection circuits
• Battery-powered power-management systems
• Automotive electronic modules
• Communication equipment power inputs
• Industrial controller power circuits
• Server and networking power systems

Industries

The EP21 series can be used in a range of industries, including:

• Automotive electronics
• Industrial automation
• Telecommunications
• Data centers and networking
• Consumer electronics
• Medical electronics
• Renewable-energy systems
• Robotics
• Test and measurement
• Smart home and building automation

Usage Ideas

1. High-Current Buck Converter Filter
   Add an EP21 choke to the input or output of a high-current buck converter to reduce common-mode conducted noise on a low-voltage supply rail.

2. Automotive Accessory Power Module
   Use the choke in a 12V-to-5V or 12V-to-3.3V converter module to improve EMC performance for infotainment, sensor, or control electronics.

3. Industrial Controller Power Entry Filter
   Include an EP21 device in the low-voltage DC input stage of a PLC, motor controller, or embedded industrial computer to limit noise transfer between external wiring and internal circuitry.

Conclusion

TDK EP21 flat-wire common-mode chokes provide a practical solution for high-current EMI filtering in compact surface-mount designs. With current ratings up to 35A, low DC resistance, and inductance values from 160µH to 640µH, they are well suited to DC-DC converters and low-voltage EMC protection applications across automotive, industrial, communications, and power-management systems.