POLY-FUSE? Resettable PTCs Surface Mount > 2920L Series # Technical Documentation: 2920L185DR EMI Filter
Manufacturer : LITTELFUSE
## 1. Application Scenarios
### Typical Use Cases
The 2920L185DR is a surface-mount EMI filter array designed for suppressing electromagnetic interference in digital circuits. Typical applications include:
- High-speed digital interfaces : USB 2.0/3.0, HDMI, Ethernet ports
- Mobile devices : Smartphones, tablets, and wearable technology
- Computing systems : Motherboards, graphics cards, and storage devices
- Automotive electronics : Infotainment systems and control modules
- Industrial controls : PLCs, sensors, and communication modules
### Industry Applications
- Consumer Electronics : Provides EMI suppression in compact devices where board space is limited
- Telecommunications : Filters noise in communication ports and RF circuits
- Automotive : Meets automotive EMC requirements for electronic control units
- Medical Devices : Ensures compliance with medical equipment EMI standards
- Industrial Automation : Protects sensitive control circuits from electrical noise
### Practical Advantages and Limitations
Advantages:
- Space Efficiency : Integrated multi-channel design reduces PCB footprint by up to 60% compared to discrete components
- Improved Reliability : Monolithic construction enhances mechanical stability and thermal performance
- Simplified Assembly : Single component placement versus multiple discrete filters reduces manufacturing complexity
- Consistent Performance : Tight tolerance matching between channels (typically ±20%)
- High-Temperature Operation : Rated for -55°C to +125°C operation
Limitations:
- Fixed Configuration : Limited to specific capacitance values and channel counts
- Current Handling : Maximum 500mA per channel may be insufficient for power applications
- Frequency Range : Optimal performance between 10MHz to 1GHz, with reduced effectiveness outside this range
- ESD Sensitivity : Requires careful handling during assembly to prevent electrostatic damage
## 2. Design Considerations
### Common Design Pitfalls and Solutions
Pitfall 1: Improper Grounding
- Issue : Inadequate ground connections leading to reduced filtering effectiveness
- Solution : Implement solid ground planes with multiple vias connecting to the filter ground pads
Pitfall 2: Signal Integrity Degradation
- Issue : Excessive capacitance causing signal rise time degradation in high-speed lines
- Solution : Verify signal timing margins and consider lower capacitance alternatives for critical timing paths
Pitfall 3: Thermal Management
- Issue : Overheating in high-current applications due to insufficient thermal relief
- Solution : Incorporate thermal vias and ensure adequate copper area for heat dissipation
### Compatibility Issues with Other Components
Digital ICs:
- Compatible with most CMOS/TTL logic families
- May require series termination resistors when used with high-speed processors
Power Supplies:
- Works effectively with switching regulators and LDOs
- Avoid placement near high-frequency switching nodes to prevent coupling
RF Components:
- Generally compatible but may introduce minor insertion loss in RF paths
- Consider alternative filtering solutions for sensitive RF receiver circuits
### PCB Layout Recommendations
Placement:
- Position as close as possible to noise sources or sensitive components
- Maintain minimum 1mm clearance from other components for accessibility
Routing:
- Keep filtered and unfiltered traces physically separated
- Use 45-degree angles for trace bends to minimize impedance discontinuities
- Maintain consistent trace widths matching characteristic impedance requirements
Grounding:
- Implement dedicated ground pour under the component
- Use multiple vias (minimum 4) connecting to the ground plane
- Ensure ground return paths are short and direct
Power Distribution:
- Decouple power pins with 100nF ceramic capacitors placed within 2mm
- Use wider traces for power connections to minimize voltage drop
## 3.
