Creating Connectors and Cables that Maintain Signal Consistency
In the world of high-speed electronic systems, maintaining signal integrity is paramount. This article provides best practices for designing connectors and cables to ensure reliable data transmission, focusing on high-speed applications.
Understanding the significance of controlled impedance is the first step. By adhering to design guidelines, we can prevent signal distortion, reduce reflections, and minimise crosstalk. The design process involves understanding why controlled impedance is necessary, following stack-up design guidelines, and learning how to design for impedance.
The current in a cable assembly propagates between the transmission line and the reference wire. For good signal integrity, it's essential that connectors and cables have a uniform impedance. In high-frequency applications, this uniformity reduces attenuation and mitigates potential FCC issues such as radiation.
A well-designed connector should ensure the return path is accessible for signals. Every signal transmitted through a wire requires a return path, which can be either power or ground. In complex systems, dispersing grounds in between signals is crucial for high-speed designs.
To avoid Electromagnetic Interference (EMI), the reference wire should always be grounded. In cables, it's important to ensure that connectors and cables have enough ground points for each wire to access a nearby reference conductor.
Keven Coates, Senior Electrical Engineer at Fluidity Technologies, with 28 years of industry experience, recently discussed the importance of signal integrity in electronic systems. He emphasised that it depends on the entire system, not just the circuit board.
Best practices for designing connectors and cables include:
- Selecting connectors matched to electrical ratings and compatible with wire gauge and pitch to avoid contact resistance and intermittent faults.
- Maintaining impedance control throughout the signal path, including at PCB-to-harness transition points, connectors, and cables, to prevent reflections and signal distortion.
- Using proper trace geometry on PCBs, such as controlled impedance traces and sufficient spacing, along with shielding where necessary, to minimise EMI and crosstalk.
- Implementing strain relief and structural supports to protect solder joints and prevent mechanical stress that could degrade signal quality over time.
- Employing environmental protections like overmolding, potting, or connectors with high ingress protection (IP) ratings to prevent moisture and dust ingress that could impact signal performance.
- Designing connectors and cables for minimal length and simplified routing to reduce attenuation and jitter, which negatively affect timing and signal detection, especially as data rates increase.
- Choosing connectors that ensure precise mechanical alignment and mating to avoid insertion errors that can compromise electrical integrity.
- For high-speed data interfaces (e.g., USB-C), ensuring careful PCB layout with proper ground planes and trace routing to manage EMI and support high data rates without signal degradation.
Following these guidelines helps maintain high signal-to-noise ratios, reduces jitter and intersymbol interference, and supports reliable high-speed data transmission in complex systems.
However, it's important to note that this article does not provide information on how to download the Controlled Impedance Design Guide. For more detailed information, consult the appropriate resources.
In a cable assembly, the reference conductor acts as a reference plane, providing uniform impedance and ensuring there are no radiated emissions. For optimal signal integrity, the source, transmission line, and receiver impedances must match.
In conclusion, understanding and implementing these design principles for connectors and cables is crucial for maintaining signal integrity in high-speed applications, ultimately ensuring reliable, efficient, and high-performance electronic systems.
In data-and-cloud-computing, controlled impedance technology plays a vital role in ensuring signal integrity. By designing connectors and cables with uniform impedance, we can prevent reflections, signal distortion, and attenuation, particularly in high-frequency applications.
Following best practices for controlled impedance design, such as selecting compatible connectors, maintaining impedance control, and using proper trace geometry, contributes to reliable high-speed data transmission and supports the efficient operation of electronic systems.
