Blog · Category
11 articles
PCB
Scope: Why some products show broadband radiated emissions from 30 MHz–1 GHz, why issues often persist up to 400 MHz–1 GHz even on multilayer boards, and how to prove and fix the root cause fast. 1) What “broadband” really means in RE On the plot, broadband looks like a wide hum
Francesco Poderico · · 4 min read
PCB
Thermal-relief “spokes” help solderability, but they add inductance and cut slots in your reference plane—exactly where high-frequency return current needs a short, wide path. For HDMI, PCIe, and other multi-GHz links, prefer solid connections to ground on anything that carr
Francesco Poderico · · 2 min read
PCB
Over the last ten years, I have seen so many PCBs fail conductive immunity that I could write a book about it. In most cases, the errors are caused by bad designs and a lack of understanding of the ground plane's role. Since I keep seeing people recommend designing 2 layers PCBs to save a few pence,
Francesco Poderico · · 2 min read
PCB
As part of my job, I have been analyzing PCB layouts that have been designed by third parties. Whenever I do this, it is interesting to see what typical mistakes people make when they are doing this. As an example, for some reason, when there is a differential signal, such as USB, RS485, etc., peopl
Francesco Poderico · · 3 min read
PCB
In today's world, ribbon cables are widely used as a way to interconnect PCBs with each other. They are low-cost and very easy to install. In spite of this, they come at a price. It is very important that you know how to choose how the current flows on each pin, otherwise, you may get into a lot of
Francesco Poderico · · 3 min read
PCB
Some time ago, I wrote a blog post about the design technique I use when I am solving EMC emissions for clients when I am working on their projects. As a result of some comments (from LinkedIn), I feel that the subject is not fully understood by the majority of people. As a result, I decided to rewr
Francesco Poderico · · 3 min read
PCB
I designed my first general I/O PCI card when I was a student (a few years ago now :-)). The PCI card was part of my thesis, and the design was challenging at the time. One of my professors was quite impressed with my throughput. The FIFO was bigger than I needed, and I managed to get all the data
Francesco Poderico · · 2 min read
PCB
To avoid EMI and crosstalk on both PCB traces and connectors, it is crucial to understand the return path current. Previously, I discussed how a ground plane reduces EMC problems (both emission and immunity). In addition to minimising crosstalk, a ground plane helps minimise interference. You know I
Francesco Poderico · · 1 min read
PCB
When we place our bypass capacitors on a PCB, there are several factors that may affect the series inductance of the capacitor ESL when it is placed on the board. What can we do in order to minimize it during the routing of our PCB? Do you consider the footprint of the capacitor when you select the
Francesco Poderico · · 2 min read
PCB
Recently, a customer contacted me about the possibility of "fixing" their design from the standpoint of EMC. The board may function perfectly, but it won't pass most tests, including Conductive Immunity, Radiated Immunity, Radiated Emission, and Conductive Emission. Some people may think a ground/V
Francesco Poderico · · 2 min read
PCB
Have you ever seen corrosion on the solder joints on an old PCB? Or on the aluminium side of a power supply? Why we do have corrosion, and how can we stop it? Every time we connect different metals with different Fermi levels, the chances are you have created a diode. Zener diodes work just based o
Francesco Poderico · · 1 min read
