signal integrity in complex flexible circuits designs

Printed circuit boards (PCBs) that are designed with signal integrity in mind can ensure the highest quality performance. Maintaining optimal signal integrity in a circuit board can prevent performance glitches or even catastrophic failures in your electronic devices. In this article, we’ll take a look at four key areas of PCB design that can influence signal integrity and how you can analyze the impact of these factors using the Signal Integrity extension in Autodesk Fusion.

As devices continue to run at ever-increasing speeds, it is critical that you take proper care to protect signal integrity in high-speed circuits. This includes ensuring that high-speed signals can reach their destination with the correct timing, duration and voltage amplitude, as well as that clock streams remain synchronized and transmission line effects are suppressed over long flexible circuits PCB traces. Fortunately, you can avoid many of these problems by carefully configuring the board layer stackup and components placement.

When it comes to high-speed digital signals, the shortest rise and fall times possible are ideal for maintaining signal integrity. The shortest time between the start of a digital pulse and its end is referred to as the slew rate of the control device and ideally should be 2-3NS. In addition, it is important that the shortest duration of a signal be no more than 50ms in order to minimize noise in the circuitry.

How do you ensure signal integrity in complex flexible circuits designs?

To further protect signal integrity in a high-speed circuit, it is necessary to use a solid copper ground plane on the PCB. However, this can limit the flexibility of a flexible or rigid-flex circuit since the copper ground plane is anchored to the PCB via the component mounting holes. In this case, a good alternative is to use a conductive ink on the ground plane which offers increased flexibility.

Another area of concern for signal integrity in high-speed circuits is crosstalk between traces. This occurs when a stronger signal pulse overwhelms a weaker one, which can cause the weaker signal to mimic its own pulse instead of transmitting its intended information. This can occur between traces routed side-by-side, or between layers of the circuit board. To reduce this issue, you can optimize your design by minimizing the distance between signal traces and routing them over separate ground planes.

In addition to preventing electromagnetic coupling between signal traces, you can improve the slew rates of your high-speed digital signals by selecting appropriate drive technologies. For example, the use of an FPGA with a fast DAC can enable you to achieve faster slew rates and lower noise levels.

Achieving signal integrity in a complex flexible circuits design can be challenging, but it’s essential to the overall performance of your electronic device. By following these guidelines and taking advantage of the specialized analysis features in your CAD system, you can ensure that your high-speed signaling design will function as intended. To get started, try out the full suite of PCB design features and world-class CAD tools in Altium Designer on the cloud today.