BROADBAND: RF & WIRELESS # Technical Documentation: CX6020 Common Mode Choke
## 1. Application Scenarios
### Typical Use Cases
The CX6020 common mode choke is primarily employed in electromagnetic interference (EMI) suppression applications across various electronic systems. This surface-mount component effectively attenuates common mode noise while allowing differential signals to pass unimpeded.
Primary implementations include:
- Power supply filtering in switch-mode power supplies (SMPS)
- Signal line integrity protection in high-speed data interfaces
- Motor drive systems for brushless DC and stepper motor controllers
- LED lighting drivers to meet EMI compliance requirements
### Industry Applications
Automotive Electronics:
- Engine control units (ECUs)
- Infotainment systems
- Advanced driver assistance systems (ADAS)
- Electric vehicle power management systems
Consumer Electronics:
- Smartphone charging circuits
- Television power supplies
- Computer peripherals (USB, HDMI interfaces)
- Gaming console power management
Industrial Automation:
- PLC I/O modules
- Industrial networking equipment
- Motor control drives
- Sensor interface circuits
Telecommunications:
- Network switches and routers
- Base station power systems
- Fiber optic transceivers
- Wireless access points
### Practical Advantages and Limitations
Advantages:
- High common mode impedance (typically 600Ω @ 100MHz)
- Compact footprint (6.0mm × 6.0mm × 2.0mm)
- Excellent temperature stability (-40°C to +125°C operating range)
- Low DC resistance (< 0.1Ω typical)
- High current handling capacity (up to 4A depending on model variant)
Limitations:
- Limited differential mode noise suppression compared to dedicated differential chokes
- Saturation current constraints require careful current rating selection
- Frequency-dependent performance with reduced effectiveness outside specified bandwidth
- Board space requirements for proper clearance around component
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Inadequate Current Rating Selection
- Problem: Choosing a choke with insufficient current rating leads to magnetic saturation and performance degradation
- Solution: Calculate peak current requirements including transients, then select choke with 20-30% margin above maximum expected current
Pitfall 2: Improper Frequency Range Selection
- Problem: Selecting choke with impedance peak outside the target noise frequency band
- Solution: Analyze noise spectrum and choose choke with maximum impedance at problematic frequencies (typically 10-100MHz for SMPS applications)
Pitfall 3: Incorrect Placement in Circuit
- Problem: Placing choke too far from noise source reduces effectiveness
- Solution: Position choke as close as possible to noise generation point (e.g., switching transistor in SMPS)
### Compatibility Issues with Other Components
Power Semiconductor Compatibility:
- Ensure choke saturation current exceeds MOSFET/IGBT peak switching currents
- Consider dv/dt ratings when used with fast-switching semiconductors
Capacitor Interactions:
- Properly match choke with X and Y capacitors for effective π-filter configurations
- Avoid resonance issues by ensuring choke self-resonant frequency doesn't align with switching frequency harmonics
IC Interface Considerations:
- Verify choke doesn't introduce unacceptable signal integrity degradation in high-speed interfaces
- Consider differential mode insertion loss for sensitive analog circuits
### PCB Layout Recommendations
Placement Guidelines:
- Position immediately after noise source (e.g., switching node in SMPS)
- Maintain minimum 2mm clearance from other magnetic components
- Avoid placement near high-heat components (>85°C)
Routing Considerations:
- Keep input and output traces separated to prevent capacitive coupling
- Use ground plane beneath choke but avoid creating ground loops
