Guide for Creating Connectors and Cables for Signal QualityAssurance
In the world of high-speed electronic designs, maintaining signal integrity is paramount. Keven Coates, Senior Electrical Engineer at Fluidity Technologies, emphasizes the importance of cables and connectors in achieving good signal integrity.
To ensure uniform impedance, several best practices must be followed. First and foremost, proper cable and trace geometry is crucial. This involves maintaining consistent conductor width, spacing, and thickness to achieve the target characteristic impedance. In printed circuit boards (PCBs), this requires calculating and controlling trace width, spacing, and stackup layers to match the impedance requirements precisely.
Second, materials with stable dielectric properties should be selected. High-quality materials such as Rogers or Teflon are recommended for PCB substrates or cables to ensure stable impedance along their lengths.
Third, symmetry in differential pairs should be maintained. Route differential pairs symmetrically with constant spacing to preserve differential impedance and minimize imbalance. Avoid placing components or vias between differential pairs, which cause impedance discontinuities and degrade signal integrity.
Fourth, controlled trace and cable lengths are essential. Matching the lengths of related signals (e.g., differential pairs) helps avoid timing skew and impedance mismatch.
Fifth, adequate spacing should be maintained to reduce crosstalk. Maintain minimum spacing rules such as at least 3 times the trace width (3W) between adjacent single-ended traces and 5W between differential pairs and other signals. For clock signals, a greater keep-out area (~50 mil) is recommended.
Sixth, impedance discontinuities caused by connectors or components should be minimized. Use impedance-controlled connectors and place coupling capacitors symmetrically to reduce their effect on impedance.
Lastly, impedance should be verified after manufacturing. Use Time-Domain Reflectometry (TDR) or network analyzers to measure and validate impedance uniformity and detect any reflections or discontinuities. Proper termination combined with uniform impedance ensures minimal reflections.
In a cable assembly, the current actually propagates between the transmission line and the reference wire. The leading edge of the wavefront travels down the cable, inducing capacitance throughout the transmission line.
Keven Coates, who is also working on the development of flying vehicles at Fluidity Technologies, emphasizes the need for every signal on a cable to have access to a return path to avoid Electromagnetic Interference (EMI). Every time a signal is transmitted through a wire, there should be a return path, either power or ground. In high-speed designs, it is crucial to have uniform impedance throughout the length of cables and connectors.
The Fluidity Technologies design and assembly team can provide assistance with employing cables and connectors in designs to enhance signal integrity. For more information about the capabilities of the team, visit their design service page.
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In the realm of data-and-cloud-computing, where high-speed electronic designs are prevalent, technology like controlled impedance plays a significant role in maintaining signal integrity. During the design and assembly process, Kevan Coates, working at Fluidity Technologies, emphasizes the importance of ensuring controlled impedance in cables and connectors to reduce Electromagnetic Interference (EMI) and enhance signal integrity.
