Eric Bogatin explains what happens when a signal hits the end of a PCB track and how to fix ringing caused by reflections.
Ringing caused by reflections can be fixed. What is happening and what to do? Explained by Eric Bogatin. Thank you Eric.
Links:
- Software used in the video: bethesignal.com/bogatin/vrpw3016-yoshi-animations-reflection…
- Signal Integrity Academy (use FEDSI - 3 months free): bethesignal.com/bogatin/3monthsubscription.php
- FEDEVEL courses: courses.fedevel.com/
Chapters:
Understanding reflections
Electrically Short vs. Long
The tool we are using explained
Simulating: Electrically short
Reflections on classic CMOS and standard board
Simulating: Electrically long (e.g. DDR3 / DDR4)
50 OHM impedance is not 50 OHM resistance
Simulating a buffer example
Why we get reflections
What happens when there is a reflection
Why reflection disappears
Frequency of ringing
How to eliminate reflections
Signal level change caused by termination
Source termination
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Why it's here
1 person recommends this
What people say. Recommended for understanding signal reflections and trace termination in high-speed PCB design.
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u/switchmod3in r/embedded • Recommends
On “Do I have to match trace lengths for USB on a microcontroller?”
A stub is when there’s a little dangly bit hanging off a transmission line between a transmitter and receiver. When a USB host is plugged into the port, the host is the transmitter and the uC is the receiver. The path from the port to the test points is a stub.
Unterminated and floating stubs will reflect energy. This reflection impairs the performance of high-speed signals.
Altium has some good blog posts and videos on the topic of signal integrity. Here’s one relevant post: https://resources.altium.com/p/stubs-transmission-lines-what-do-they-do-and-how-do-you-keep-them-happening
and a video: link to this video
