Power integrity posts. All in one place.

Video: PDN Measurement with a Network Analyzer

April 2, 2020 by Rolf Ostergaard

See how easily you can do a PDN measurement using a network analyzer or VNA in the video here. Building solid power distribution systems (PDN’s) is maybe the most important learning from the signal integrity training overall. Because it matters. Both for the logic functions, the signal quality (integrity) and for the radiated emissions (EMI).… Read more

How much Bypass does the Zynq have On-chip?

April 9, 2014 by Rolf Ostergaard

So just how much bypass do you need for a Xilinx Zynq FPGA? Good question. It is quite obvious from looking at the chip itself that a significant amount of bypass is already implemented on the package itself. But how much is that exactly? A simple ohmmeter test shows that four of the caps are… Read more

Bypass capacitor placement is irrelevant

March 21, 2014 by Rolf Ostergaard

Lots of people fuss over the exact bypass capacitor placement. Why? Lots of app notes have fluffy comments like “place as close as possible” when it comes to bypass capacitors. Why? The fact of the matter is: With fairly solid and closely coupled power and ground planes, the exact placement of bypass capacitors is not… Read more

ZedBoard Bypass Measurements

March 21, 2014 by Rolf Ostergaard

There has been a lot of discussions (on this blog, on LinkedIn and on Electronics StackExchange) about the bypass scheme on the ZedBoard (a Xilinx Zynq FPGA eval board distributed by Avnet/Silica). It made sense to do some actual measurements on the board instead of relying purely on speculations. It is clear from the funny… Read more

PDN ground offset error when doing measurements

March 13, 2014 by Rolf Ostergaard

Is there a risk of ground offset error when doing PDN measurements? This is another question that popped up after the story about what happens when the test points are moved in a network analyzer setup for measuring bypass (or PDN – Power Distribution Network) on a board is: Would it change anything if the… Read more

Measuring PDN on a populated board

March 2, 2014 by Rolf Ostergaard

How about measuring the Power Distribution Network – or PDN – on a populated board? The post on the importance of the distance between the measurement points used when measuring the impedance of all the bypass capacitance on a board triggered another round of questions. Good. One of them is: Why not do a populated… Read more

PDN measurement points: Does it really matter?

February 23, 2014 by Rolf Ostergaard

What would change if you move the PDN measurement points when you measure the PDN using a network analyzer? Ever since I did the video on how to use a network analyzer to measure the resulting impedance of all the bypass capacitors on a board, this question keeps coming up. One could speculate that two… Read more

Does the Zedboard bypass scheme make sense?

January 22, 2014 by Rolf Ostergaard

A question came up: Does the Zedboard bypass scheme make sense? The Zedboard is an eval board for the Xilinx Zynq-7000 FPGA. As such it may be nothing special, but when you look at the board you will notice a very interesting pattern of bypass capacitors. And there is a long story on the web… Read more

How to specify bypass capacitors

April 2, 2013 by Rolf Ostergaard

EDN Europe March issue had signal integrity as the key theme. I think that is great and we need more stories like that, but that is not a big surprise I guess. Two stories caught my eye: “Signal-Integrity Issues on the Rise” and “Why your 4.7-uF ceramic cap becomes a 0.33-uF cap”. The first is… Read more

PDN optimizer as a free webtool

January 21, 2013 by Rolf Ostergaard

An automatic PDN optimizer? For free? Yes – find the right number and types of decoupling/bypass capacitors quickly. This is exactly what this new free web tool does right in your browser. No install. No download. And you get to try it out first… (almost)… Figuring out how to design a solid bypass and power… Read more