High-Frequency Applications with Polymer Capacitors
Guidelines for using NCC polymer capacitors in high-frequency applications including EMI filtering, power integrity, and switching circuits. Learn about the advantages of polymer technology in demanding high-frequency environments and how to optimize performance.
Introduction to Polymer Capacitors in High-Frequency Applications
Conductive polymer capacitors represent a significant advancement in capacitor technology, particularly for high-frequency applications where traditional aluminum electrolytics face limitations. NCC's polymer and hybrid capacitors feature extremely low Equivalent Series Resistance (ESR) values that remain stable across a wide frequency range, making them ideal for high-frequency filtering, decoupling, and power integrity applications.
Unlike aluminum electrolytic capacitors, whose ESR increases significantly at high frequencies due to electrolyte limitations, polymer capacitors maintain low ESR values up to MHz ranges, providing superior performance in modern high-frequency circuits. This characteristic makes them particularly suitable for applications in power electronics, telecommunication, and automotive domains where high-efficiency operation is critical.
Key Advantages in High-Frequency Applications
Ultra-Low ESR
Polymer capacitors typically exhibit ESR values in the milliohm range, significantly lower than aluminum electrolytics, especially at high frequencies. This results in reduced I²R losses and improved efficiency.
Frequency Stability
ESR and capacitance values remain stable across wide frequency ranges, unlike electrolytics which become inductive and lose effectiveness at high frequencies. This stability ensures consistent performance across the application's frequency spectrum.
Low Temperature Sensitivity
Performance remains stable at low temperatures where electrolytics become resistive. This attribute is particularly valuable for automotive and aerospace applications with wide temperature ranges.
Enhanced Ripple Handling
Capable of handling significant ripple current with minimal heating due to ultra-low ESR, making them ideal for high-frequency switching power supplies and DC-DC converters.
EMI Filtering Applications
Electromagnetic Interference (EMI) filtering represents one of the most important applications for NCC polymer capacitors in high-frequency systems:
Conducted EMI Suppression
Polymer capacitors excel in both differential-mode and common-mode EMI filtering stages due to their low ESR and stable impedance characteristics over frequency. In switching power supplies:
- Input filtering: Reduces noise injection back to AC source and prevents interference with other equipment
- Output filtering: Minimizes output ripple voltage and conducted emissions
- Snubber circuits: Absorb switching transients that contribute to EMI generation
Layout Considerations
For optimal EMI performance with polymer capacitors:
- Minimize loop inductance with short, wide traces connecting to the capacitor
- Use multiple vias to connect to ground plane for low-inductance connection
- Place capacitors as close as possible to noise sources or sensitive circuits
- Consider using multiple capacitors in parallel for enhanced broadband performance
| Application | NCC Series | Frequency Range | Key Parameters |
|---|---|---|---|
| DC-DC Converter Output | CL21/CCAP | 100kHz - 10MHz | Ultra-low ESR, high ripple capability |
| High-Frequency Decoupling | CL21/CCAP | 1MHz - 100MHz | Low ESL, stable impedance |
| Snubber Circuits | CCAP Series | 20kHz - 500kHz | High ripple, low loss |
| Radiated EMI Suppression | CL21 Series | 30MHz - 300MHz | Stable characteristics, low losses |
Power Integrity Applications
In modern digital systems with high-speed processors, FPGAs, and ASICs, power integrity has become critical. NCC polymer capacitors help maintain clean power rails:
Decoupling Applications
For effective power rail decoupling, polymer capacitors play a crucial role:
- High-frequency decoupling: Use small value polymer caps (0.1µF - 10µF) placed closest to IC power pins to minimize inductance loops
- Mid-frequency decoupling: Use medium value caps (10µF - 100µF) as intermediate energy storage to maintain low impedance at switching frequencies
- Low-frequency support: Use larger value caps for bulk energy storage to respond to lower-frequency load transients
Simultaneous Switching Noise (SSN) Mitigation
Polymer capacitors effectively suppress SSN due to their low ESR and stable impedance characteristics. This is particularly important in systems with high pin counts and fast logic transitions. The predictable performance of NCC polymer capacitors ensures consistent noise suppression across temperature and frequency ranges.
Design Guidelines for High-Frequency Applications
Component Selection
+When selecting polymer capacitors for high-frequency applications:
- Consider the frequency range of your application and select caps with minimum impedance in that range
- Pay attention to self-resonant frequency (SRF) and ensure it's above your operating frequency
- Consider DC bias effects on capacitance value (less significant in polymer than ceramic)
- Ensure voltage derating is appropriate for your operating conditions
- For automotive applications, select AEC-Q200 qualified series such as NCC's automotive-grade polymer options
PCB Layout Guidelines
+For optimal high-frequency performance:
- Minimize trace inductance by using wide, short traces from capacitor terminals to power/ground planes
- Maximize via count to ground plane, use multiple parallel vias for the shortest return path
- Minimize loop areas for current return paths to reduce inductance
- Use solid ground and power planes where possible to provide low-impedance return paths
- Consider using multiple smaller capacitors in parallel rather than single large ones to reduce overall ESL
Thermal Considerations
+Though polymer capacitors generate less heat due to low ESR, thermal management remains critical:
- Consider thermal management in high-power applications, especially when multiple high-frequency ripple currents are present
- Allow adequate spacing for air circulation around capacitors
- Consider thermal vias to dissipate heat to inner layers, particularly for larger polymer capacitors
- Monitor temperature in high-ripple applications; polymer capacitors maintain performance better than electrolytics at elevated temperatures
Testing and Validation
+For high-frequency applications, validate performance with appropriate test methods:
- Impedance analyzer measurements to verify ESR and ESL at operating frequencies
- Spectrum analyzer evaluation of EMI reduction effectiveness
- Oscilloscope measurements of transient response and ripple reduction
- Thermal camera inspection for hotspots and thermal distribution
- Life testing under actual application conditions to validate performance over time
FAE Note: For applications with switching frequencies above 1 MHz, NCC's polymer capacitors provide superior performance compared to traditional aluminum electrolytics, which become inductive due to ESL effects. The ultra-low ESR and stable frequency characteristics of polymer series allow for more effective high-frequency filtering and better transient response. In automotive applications, polymer capacitors also provide enhanced reliability due to their solid construction without liquid electrolyte.