Strategies to Optimize Propagation Delay in Your PCB Design

Amit Bahl

CRO
Sierra Circuits

How to optimize propagation delay

Propagation delay (t_pd) is the measure of the time delay experienced by a signal as it travels from its source to its destination through various nets and vias. High-speed data transfer interfaces such as DDR5, HDMI, Ethernet, PCI-e, and USB are prone to time delay issues. Synchronization between clock and data signals is paramount to preventing data corruption.

We’ll cover the following aspects to help you compensate for t_pd in your designs:

Propagation delay in PCBs mainly depends on factors such as the effective dielectric constant (Ereff) of substrates, parasitic capacitance, dielectric thickness, and inductance and capacitance of a given trace. In case of microstrips, the Dk of the surrounding air and solder masks also matter.

Always choose high-speed substrates with low Dk (< 4) and Df (~ 0.001) for reduced dispersion, losses, and delay. To calculate an accurate t_pd, you need to know the clock skew, pin-package delays, and the timing tolerances of all the components on your board.

The impact of time delay variations can be compensated by implementing appropriate trace configurations with controlled impedances. This should be followed by length matching, where the differential pairs’ trace lengths are equalized.

To ensure signal integrity, you should stick to the critical length guidelines when designing controlled impedance traces.

In this webinar, our PCB design experts will take you through the steps to calculate and optimize propagation delay for reliable high-speed signal transmission.

What you’ll learn:

• Factors that affect propagation delay in your PCB
• Quick methods to calculate t_pd
• Choosing dielectric materials to efficiently control propagation delay and reduce signal losses
• Impact of critical length, shortline, and 3dB bandwidth on propagation delay
• Controlling t_pd by meandering/delay tuning using Altium Designer
• High-speed PCB design rules to mitigate propagation delay problems

Presented by Amit Bahl

Amit has been in the PCB industry for 20+ years. He is the Chief Revenue Officer at Sierra Circuits. His passion is to empower tech companies to achieve their visions and change the world. Rockets going into space, self-driving cars taking up the streets, cancer-fighting medical devices, protecting the country, he’s ready to build any circuit board!