Hi Everyone, I am Beginner, In fact, I got a little lost while learning the Signal Integrity issues that every designer of PCBs face. But I found a helpful video of my problem by Eric Bogatin, who is well known in the field, He is speaking about: The Six Families of SI/PI/EMC Noise Problems.
Useful video and this is its link:
He said this Families are:
1- Reflection noise
2- Cross talk
3- Ground (and power) bounce
4- Losses (@ Gbps)
5- Rail collapse, voltage droop, power supply noise
And hes said, the ONLY thing that causes a reflection is Impedence mismatch exactly.
So my Question is:
What is just the name of the Solutions for EACH ONE of this Six Families Noise Problems? just tell me the title of the the Solutions or Techniques to do with Kicad Features.
Controlled Impedance Traces in Kicad? Length Tuning in Kicad? What Else? Please tell me for EACH ONE of this Six Families.
Please tell me when you use: Differential Pair Routing and Trace Length Matching? With USB Traces for example?
And What about EMI Issues? It is the same as EMC Issues? Its is the same thing?
EMC, the “C” is for Compatibility. EMI, the “I” is for Interference. Thus, EMC covers EMI and other EM-influences.
EMC is about the hardware and design - Kicad’s default tools may not help with your particular need(s).
You may find useful Plugin’s that help (not sure).
I can recommend an Excellent Book that helped me 25 yrs ago and covers the questions you ask but, is still relevant and has good ‘Design’ section. I taught designing for EMC when I worked at AMP (now, Tyco).
Your 6 minute video is just an introduction to what the guy is going to say next. I assume he goes deeper into the subject in the rest of the talk.
For digital circuits, the two most important measures are to have effective decoupling capacitors, and a good (nearly) uninterrupted GND plane. The decopling capacitors ensure that the IC’s are not starved of supply voltage during transients (Where the wiring inductance prevents “instant” power to be delivered to an IC), and a good GND plane mitigates effects of GND bounce and most of the EMI issues and some signal integrity issues.
Taking care of these two issues usually gets you 80% of the way for relatively simple circuits such as a microcontroller circuit with a bunch of surrounding chips.
The other issues are not such a big problem for “slow” microcontrollers (upto 20MHz or so), but become more important at higher frequencies. (Or more correct: when the rise time of signals decreases It is the speed of the flanks that count, not the overall clock frequency).
Cross talk is an issue that gets worse when PCB tracks are next to each other over a long length. For this it is better to not route the tracks from long data (or address, or other) busses next to each other, but
“USB” is also not a single standard. With the old low speed (1.5Mbps, still used for HID such as keyboard and mouse) it’s not very critical, but the latest USB standards go over 3Gbps and then the smallest detail becomes important, and differential pair routing is a must.
Length tuning is an important issue when the time difference between a whole lot of signals becomes important, for example with DDR chips that have a lot of datalines and clock and latch signals, and everything works at high speeds. Electric signals do not go “instantly” through a copper PCB track. Their speed is usually between 60% and 85% of light speed and this can not be neglected anymore in electronics.
EMI:
EMC:
Reading a book such as BlackCoffee posted is a good idea. There are many thick books written on these subjects.
EMC is a big subject. I have posted some links recently:
And some more few posts later in the same thread.
I see there only 5 points. The few word about possible solutions:
1- controlled impedance,
2- separation (distance and shielding (for example GND track between cross talking tracks)),
3- blocking capacitors and connecting to power through ferryte bead,
4- I didn’t looked that video - losses for me are rather connected to long cables and not PCB, but everything probably depends on frequency,
5- filters, brown-out protection.
That is the main thing you need to determine. Is the output impedance of stage A equal to the input impedance of stage B, given that stage B plugs into stage A (for example, maybe A is an preamp. and B is an amplifier) at the frequency at which you plan to drive A’s output. Impedance is a function of frequency. It is not just plain resistance.
First determine the frequency at which stage A operates. Then search through the reference materials to try to figure out a way to measure the two impedances I mentioned.
1: Proper impedance matching (KiCad calculator helps).
2: conductor spacing, guard vias, guard traces, proper placement, digital/analog separation, increase layer count, etc. Plenty of books and information available on this. I like High Speed Digital Design by Howard Johnson.
3 - 5: as @paulvdh said, proper selection and placement of capacitors
4: Keep high frequency traces short. Also as @paulvdh said don’t run them over gaps in ground planes.
Boards are cheap enough these days if I have a question about a design, I’ll lay the circuit out two different ways and compare the results.
