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PCB Design Blog

10 Oct, 2012

Return current on a stripline

Posted by Patrick Carrier

Patrick Carrier

In previous blogs, I have discussed the importance of an uninterrupted, intact reference plane for signals.  But, what if you have two reference planes for your signal?  This is probably true of most signals in any board over 6 layers – a great deal of routing exists on the inner layers.  In a symmetrical stripline, the return current is shared equally between both planes.  So, both planes need

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9 Oct, 2012

Is it ever okay to cross a plane split?

Posted by Patrick Carrier

Patrick Carrier

NO. Okay, well, I guess you could say “it depends”, but in general, no, it is not okay to cross a plane split. Why not? Basically, you are creating a break in the current return path for the signal.  That turns your trace/plane combination into more of an antenna than a transmission line.  And if you are radiating energy, that means you are not transmitting energy to your receiver.  So,

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8 Oct, 2012

Collective Intelligence

Posted by Michael Ford

Michael Ford

We learn different things in different ways. Which are the ways in which we learn that we enjoy and more importantly can trust? When I was at school, I veered towards the sciences, especially physics, electronics and maths, I guess very much in common with those of us in this industry. I steered well clear of subjects such as history and geography. For me, there seem to be four elements that contributed

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8 Oct, 2012

Patrick Carrier

Many electromagnetic interference (EMI) problems on PCBs happen when antennas are unintentionally created on the board.  How can this be avoided?  By making sure currents, especially high-frequency currents, travel in a loop.  On high-speed lines, that loop is made up of a PCB trace AND the reference plane below it.  Put a break in either one, and you’ve created an antenna.  Obviously you would

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4 Oct, 2012

Gary Lameris

As I drove home last night from the office, the spectacular fall colors were on display in Colorado. The views on the rolling foothills were stunning; deep green manicured grass, orange and red non-native trees, and the brilliant yellow of the native Aspen trees all placed against a sky filled with clouds of dark blue grays, and muted yellows of dry grasses. Mentor Graphics’ DxDesigner has long

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28 Sep, 2012

Gary Lameris

With the new DxDesigner 7.9.4 release, a primary focus of the release was improving the ‘ease of use.’  The project navigator is a powerful tool and is extremely configurable per user, and also has the ability to show component names, reference designators, page numbers, net names, blocks, and other helpful functions. But as the old saying goes, pictures are worth a thousand words and that is the driver

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10 Sep, 2012

Show Me The Data – Are You Crazy?

Posted by Michael Ford

Michael Ford

Maybe it is just me (but I think not). It is the kind of thing that everyone assumes everyone knows, but they don’t. As a school-boy, at high school, the young Michael had to wear the school uniform. Nothing fancy, blazer, trousers, normal regular stuff, and I had all the gear. What I could not get my head around though was how come that every ten minutes I was being told off for having my shirt hanging

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30 Aug, 2012

Introducing DxDesigner 7.9.4

Posted by Gary Lameris

Gary Lameris

Welcome! I am Gary Lameris Technical Marketing Engineer for Mentor Graphics. I’ve worked with DxDesigner since 1988 and have watched it grow from the independent Unix/Dos tool called PowerView and Viewdraw to a powerful multi-user schematic drafting program tightly integrated into the Expedition Enterprise and PADS layout tools today. Four years ago I moved to Colorado to join Mentor Graphics and the

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Schematic Design

21 Aug, 2012

Jim Martens

With PADS 9.4.1, the user was given new controls during the creation and editing of drafting shapes.  You can now control how and where the cursor will snap to an oject, including  corners, midpoints, centers of arcs and circles, intersections of lines and circle quadrants, component origin, pin, and via. Bill Tkachuk, an AE for CSD, has created Technote MG579477 which includes a video “how to”

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13 Aug, 2012

The Olympics Are Over

Posted by Michael Ford

Michael Ford

It amazes me that for a couple of weeks every four years, the world is suddenly interested in sports. Not just the popular sports like football, but all kinds of sports, many of which we have only ever otherwise experienced while at school. Not fond memories of that in my case it has to be said. For athletes, it is wonderful sense of achievement to be seen and acknowledged as the best in the world.

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31 Jul, 2012

Playing Russian Roulette

Posted by Michael Ford

Michael Ford

Luckily, I have a natural aversion to gambling. This doesn’t come from a bad personal experience and I haven’t personally seen the effects that compulsive gambling can have on people. I guess it comes from the feeling of the potential for loss. I buy lottery tickets from time to time and in the name of British culture have been known to put a penny or two on the Grand National horse race. I even won

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30 Jul, 2012

Jim Martens

I’ve been presenting at a bunch of seminars throughout the world over the past few months.  One of the presentations has been about passing data from PCB design to manufacturing.  I make the point that over 90% of the time, your fabricator will edit the Gerber files to improve their yield, and most of the time, you don’t know what they change.  The attendees have shared several of their own “horror”

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24 Jul, 2012

Jim Martens

PADS – deservedly so – has the reputation of a powerful, easy to use tool.  The menus and dialog boxes are engineered to be intuitive, and easy for new users to navigate through.  Sometimes though, the task you are trying to perform can be done quicker by using Modeless commands – a “short cut” you can use rather than pulling down menus or opening a dialog box.  Many users have told me how much more

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19 Jul, 2012

Michael Ford

I read a monthly computer magazine. It is the real thing, paper and everything. Magazines are quite expensive now, in the UK, you can easily spend around £5 (US$ 7.50) on a monthly magazine.  They are full of good stuff. There are columns on various PC related subjects by the experienced, news, reviews, articles, a how-to section and lot and lots of ads. The usual stuff. How much of this though do I

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12 Jul, 2012

Zhen Mu

For SERDES channel designs, board/system designers are told to remove stubs and non-functional pads (NFP) of vias on channels to ensure signal quality at the receiver ends. What confuses them the most is when to consider these effects: does one have to remove all NFPs and stubs in any channel carrying signals with data rates over 1Gbps? Can a design still work even if via stubs are kept? The actual

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SERDES

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