Elementary, Mr. Watson: Is Your Bathroom in the Kitchen?

Several years ago, a report came out of St. Louis of a strange apartment on the market. It was in the community of Central West End. With a small floor plan of only 200 square feet, the entire bathroom was placed right in the middle of the kitchen. Well, that's interesting. It gives new meaning to the studio apartment. Well, with closer examination, there are several Watson_Nov_Fig1.jpgconvenient features available here. You got a lovely footstool to get to those pesky upper cabinets and could save even more space by removing the sink entirely and using the tub to wash those late-night dishes. But seriously, who would do something like this? Yes, it's a terrible floor plan.

Here’s my point: In this story lies some fantastic lessons for us as PCB designers. In real estate, it's pretty uncommon to find the bathroom in the kitchen; but metaphorically speaking, it's done all the time in a PCB design (ouch). What do I mean by that? Well, the floor plans of many PCBs have a lot to be desired. The subject of circuits and component placement is usually an afterthought, usually when the completed board returns, and it just doesn't work like it did on paper. Then you think, “Maybe I shouldn't put the tub next to the stove; it’s not a good idea.”

The steps of arranging the rooms into functional PCBs are often ignored or rushed through because everyone wants to get into what they consider the "exciting" part—the routing—not realizing the routing started with the placing of the very first component. Those functional areas and their locations do impact product quality. Placing the rooms or sections of your design willy-nilly is the equivalent of the tiny apartment in St. Louis with the toilet/footstool next to the kitchen sink. The advice I always give, especially to new designers is, "Just because you can do something doesn't mean you should.”

With more complex designs, the name of the game is to make it smaller and higher in performance. I refer to it as the incredible shrinking FR-4 real estate, dwindling significantly, and causing significant issues for us. We're always going through different paradigm shifts in the industry. To get everything placed and arranged correctly, we may not always "break" the rules, but we often bend them to the point they look more like a pretzel. Although PCBs are getting smaller, we don't have a license to violate the basic design principles. Just the opposite should be the case.

As the initial step of placing your components on the PCB, you should take a step back and look at the bigger and more important picture of your PCB floor plan. Several considerations drive your decisions, which I look at in more detail.

Consider Critical Placement
The first components that usually go on the PCB and are locked down are called critical components. These are the items that must have a precise location on the PCB. Driving those locations could be mechanical, testing, EMI, user interface, or design development access. Here you are taking your first steps to solving the puzzle of the PCB. Look at them as anchors for what follows. Since the first rule of good signal integrity is to keep the connections as short as possible, that drives locating the first “rooms.” That results in components like connectors being on the edge of the PCB for easy access to other essential components.

Watson_Nov-Fig2.jpg
Types of Circuits and Function
First, understand the function and the purpose of your circuit. Please don't fall into the ruse that often happens; some believe the responsibility of a designer is just to put everything on the PCB and connect the dots. Instead, dig deeper and know not just what, but rather why you are doing something.

We all know that the two sides of electronics are digital and analog. A digital circuit is one where the signal must be one of two discrete levels. Each level is interpreted as one of two states (on/off, 0/1, true/false). An analog circuit, on the other hand, is one that represents continuous signals in electrical form. These two are the “odd couple” in the electronic world. (Those younger folks in the audience might need to Google that reference.) On one side, you have Felix Unger, the neat freak, and on the other, Oscar Madison, the sloppy sportswriter. Both are divorced and end up sharing a New York City apartment. It makes for a funny sitcom but not so funny on a PCB design.

A well-designed digital/analog circuit will have isolated power and grounds. The current flows through a digital circuit vs. analog, and the varying demands on the power rail cause instabilities and spikes. The fact is that integrated circuits are susceptible to power fluctuations. Thus, the reason for capacitors on each power pin (bypass capacitors). I’ll give you this one for free: The standard practice is to have separate supplies and return paths for each circuit. In isolation, to use the modern vernacular, socially distance different sections of your design; the digital, analog, and power sections must have their own isolated working areas. I can always tell the designers that didn't take this subject seriously. Those are the boards that come back from assembly with issues of noise and EMI. It's now too late to consider that maybe Maxwell was right with his equation regarding electrical charges.

Isolation is so severe that unique components bridge the different areas (rooms). Look at this as the doorways in your home; you only move (hopefully) from room to room through the door. These areas have special rules in those areas. There lies a problem with our tiny apartment in St. Louis—no consideration of the functions of the two areas. What are the rules of interaction between them, which is what if both areas got used simultaneously? It would be a bit, let's say, awkward. The same is true of our PCB.

Watson_Nov_Fig3.jpg
‘Other’ Considerations
Within the major areas of digital, analog, and power, there are minor areas, like the closets in the master bedroom, such as keeping various components like decoupling caps close to power pins and clock drivers/synchronizers close to the clock oscillator. Oscillators must be close to their integrated input pins. Also, always isolate the outputs from the inputs to reduce feedback problems.

Finally, the need for isolation goes much deeper than the types or the circuit functions; you must consider the frequency of your design. Intermingling different circuit operating speeds causes more problems in a design. Identify the high, medium, and low-frequency circuits, then isolate them from each other. According to IPC-2221, the correct location for those high-frequency circuits is close to the connectors or source. You want short signal routes that don't go across the board. What happens with an electrical charge on a low-frequency vs. high-frequency circuit? How could they interrelate and cause problems with signal integrity, time delays, reflections, electromagnetic interference, and crosstalk? That's a discussion for another day.

In real estate or PCB design, it doesn't make sense to place your bathroom in your kitchen. It's not a good practice in your PCB design, either. Know the different major and minor areas when you look at the floor plan of your board and know the bridges (doorways) between them, keeping everything inside the room and isolated from the other. You'll have a much quieter design with fewer problems. The best part is you won't need to use a toilet for a footstool.

John Watson, CID, is a customer success manager at Altium. 

 

Download The Printed Circuit Designer’s Guide to… Design for Manufacturing by David Marrakchi. You can also view other titles in our full I-007eBooks library.

Back

2022

Elementary, Mr. Watson: Is Your Bathroom in the Kitchen?

11-10-2022

Several years ago, a report came out of St. Louis of a strange apartment on the market. It was in the community of Central West End. With a small floor plan of only 200 square feet, the entire bathroom was placed right in the middle of the kitchen. Well, that's interesting. It gives new meaning to the studio apartment. Well, with closer examination, there are several convenient features available, so here's my point: In this story lies some fantastic lessons for us as PCB designers. In real estate, it's pretty uncommon to find the bathroom in the kitchen; but metaphorically speaking, it's done all the time in a PCB design (ouch).

View Story

Elementary, Mr. Watson: Is the Tail Wagging the Dog?

10-13-2022

I recently had the opportunity to work on a rather critical PCB design project during what should have been the final design review. Unfortunately, after presenting my well-organized PowerPoint presentation, I asked the most challenging question to the group of assembled engineers and managers, “So, what do you think?” As we went around the room, nearly every comment started with something like, "You know what we could do..." Ideas flew around the room, fueling a full-blown brainstorm. Unfortunately, what followed could best be described as organized chaos. The result was that several of the suggestions took the product back to re-design, and what was supposed to be the final steps didn't happen.

View Story

Elementary, Mr. Watson: Anatomy of Your Component—Footprint, Part 2

09-08-2022

Have you ever gone to a buffet hungry and looking forward to digging in? You grab the plate and start down the food line, picking things as you go. Halfway through, your plate is stacked up with food, looking very similar to the Leaning Tower of Pisa. Then you get to the good stuff at the end of the buffet, but there’s no room on your plate. At this point, you probably feel much like that with the first part of looking at our footprint, but rest assured, although your plate is already full, the good stuff is still waiting for us. I have saved the best for our second offering.

View Story

Elementary, Mr. Watson: The Anatomy of Your Component—Footprint

08-17-2022

I hate to disappoint you if you expect to get everything about footprints from this modest column, but a short search online results in a long list of technical standards and books on this subject. So, I will only hit the surface of the discussion. I have often spoken about the parent-child relationship principle in PCB design. In this series, we have learned that we can see how that "relationship" is supported directly by the information in the component itself. As a short review, the parent-child relationship is where you use an input of data, material, or parts (parents) as the foundation or resource for another item or document (child).

View Story

Elementary, Mr. Watson: The Anatomy of Your PCB Component, Part 2

07-13-2022

In the start of my series of the anatomy of a component, I discussed that the component has two major divisions. The first is information that consists of name, description, parametric information, sourcing (part choices), and the datasheet (Figure 1). Next, the component comprises symbol, PCB footprint, 3D model, and simulation models. I gave the example of the dissection of the frog, with an analogy that every part has a purpose. In the same way, each part of our component has a distinct purpose in our PCB design, including our models.

View Story

Elementary, Mr. Watson: The Anatomy of Your PCB Component, Part 1

06-16-2022

One of the classes I dreaded the most in school each year was biology. This was because I knew it was only a matter of time before I would face the rite of passage for most high school students: dissecting a frog. It wasn’t something I ever looked forward to. We had to go through the same educational exercise and maybe with the same apprehension for most of us. But my point in bringing up the painful experiences of our high school years is, although it was difficult, I did learn a powerful lesson: Every part has a purpose.

View Story

Elementary, Mr. Watson: The Five Pillars of Your Library, Part 5—Traceability

05-12-2022

We have reached the end of this series regarding the five pillars of the component library. We now have a robust library that provides the required resources for the ever-changing industry. Above that is having a flexible library to grow with the company. The final pillar is traceability. Why is traceability so essential and considered a pillar of our library? Read on for details.

View Story

Elementary, Mr. Watson: The Five Pillars of your Library, Part 4—Review

04-14-2022

I trust that you have been enjoying this series on the five pillars of your library. Now that we have a single library managed using our revisioning, and we have lifecycle schemes organized so that we can easily find something in the component category, family, and subfamilies, we are now ready to look at one of our library's most vital principles and pillars: reviewable.

View Story

Elementary, Mr. Watson: The Five Pillars of Your Library, Part 3—Architecture

03-10-2022

Before I continue with the series of the five pillars of your library, I want to do a little review. Although every library is different, the five pillars are consistent with any sound library. You place these pillars to support a specific building section in building construction. To pull one out requires the remaining ones to hold the total weight above. So, each of these supports is needed for your library to succeed. You cannot choose which of them you intend to follow; to pull just one out results in the toppling of the others.

View Story

Elementary, Mr. Watson: The Five Pillars of Your Library, Part 2—Managed

02-17-2022

The 1972 classic movie “The Candidate” tells the story of Bill McKay (played by Robert Redford), who was running for the state senate. Although he was a long shot and an underdog, McKay ends up surprising everyone with an incredibly close win. After the concession speech of his opponent, a vast mob surrounds McKay. He fights through the crowd, trying to reach his campaign manager Marvin (played by Peter Boyle). Finally reaching him, McKay pulls Marvin aside into a hotel room, sits on the bed, and after several seconds of silence, finally asks a very intense question “So, what do we do now?” The campaign manager looks bewildered, so McKay asks the question again, “What do we do now?”

View Story
Back

2021

Elementary, Mr. Watson: PCB Data Management and Security

12-12-2021

As a grandfather of six grandchildren, one of my great joys is spending time with them. There is nothing better than spending an afternoon at the park and especially playing on the teeter-totter. It's all fun and games until grandpa gets on one side, and they try to lift me. Then the harsh reality and a teachable moment in leverage, balance, and just how heavy grandpa really is hits pretty hard.

View Story

Elementary, Mr. Watson: We’ve Never Done It That Way Before

11-11-2021

The September edition of Design007 Magazine discussed the theme of collaborating and working with a team. In that issue, I wrote a feature article called “PCB Design Is a Team Sport.” After that edition was published, I had several follow-up questions and conversations with individuals; they agreed on the importance of teamwork but felt that it's easier said than done. It's challenging because of the inherent problem of team members accepting or handling change very well. Change it's a word that sends shivers down the spine of some. You know those sort of individuals. They're easy to identify. The ones that constantly remind everyone, "We never did it that way before." As if how we did things in the past was so much better.

View Story

Elementary, Mr. Watson: First, Component Shortages, and Now Hot Dogs?

10-14-2021

When I considered the title for this month’s article, I seriously considered calling it "From the Frying Pan Into the Fire" because I’m sure you’ve noticed recently that the component shortage problem has only worsened—we’re now seeing other supply lines breaking down.

View Story

Elementary Mr. Watson: PCB Design—It's a Team Sport

09-29-2021

One of the hard lessons of this past year was about the value of the team and collaboration. I have repeatedly heard how many of us have a newfound respect and appreciation for the teams we work with inside our companies. Out of necessity, we had to find new ways to collaborate.

View Story

Elementary, Mr. Watson: The Danger of Rogue Libraries

09-16-2021

For PCB designers, the most common part of the library is the collection of components used in the PCB design process. But, I have seen some libraries have other information, including a resource area, a group of documents, standards, and articles. So basically it can have anything you want.

View Story

Elementary, Mr. Watson: Epic Fails with Design Rules

08-12-2021

Various sciences, including physics, mathematics, chemistry, are significantly involved throughout the PCB design process, rules that can sometimes be bent but not broken. However, the rules that designers break and ignore altogether and very often are the design rules.

View Story

Elementary, Mr. Watson: Managing Risk in PCB Design

08-05-2021

PCB design is like bungee jumping. With the complexity of a PCB design, the intricate details, and various steps, it's rather easy to make mistakes. Those mistakes, many times, do not show up until it's too late and the board has gone off to fabrication and assembly. By the way, a good rule is not to use your assembly house as your quality control team for PCB designs.

View Story

Elementary, Mr. Watson: Time to Market, from Ludicrous Speed to Plaid

07-18-2021

Mel Brooks may have something to teach us about going "ludicrous speed" in getting our designs to the finish line. John Watson explains.

View Story

Elementary, Mr. Watson: Trust but Verify

06-10-2021

Over many years, I have seen some elaborate PCB library systems. However, the best ones were those not based on the size but rather the quality of the information. That old axiom is definitely “not quantity but rather quality.”

View Story

Elementary, Mr. Watson: Paying the Price To Be a PCB Designer

05-13-2021

Today, the electronics industry is flourishing with innovations and technologies. The result is that the “good” designers are left in the dust. Truthfully, our industry doesn't need more good designers; rather, we need great designers—those who can face any challenge and instead of cowering in the corner, looks at the task at hand and says, "Bring it on."

View Story
Back

2020

Elementary, Mr. Watson: Demystifying Bypass Capacitors

12-17-2020

As PCB designers, we work under the simple rule of cause and effect, and a PCB design can quickly become a petri dish for the butterfly effect to flourish. One of those areas that can quickly snowball into major problems is your PCB power distribution structure. When it goes wrong, it usually goes very wrong and has significant issues throughout your design.

View Story

Elementary, Mr. Watson: Density Feasibility Putting 10 Lbs in a 5-Lb Bag

11-18-2020

Whether on a customer, a system, or a PCB level, it’s essential to understand the final objective and how you intend to get there and meet the customer need at the forefront of any project. In this column, John Watson addresses density feasibility and more.

View Story

Elementary, Mr. Watson: Location, Location, Location

10-15-2020

When it comes to PCB design, one of the most overlooked principles is component placement. Similar to a home, the component location has a considerable impact on the quality and is the real value of a PCB design. John Watson examines five rules to follow when it comes to component placement.

View Story

Elementary, Mr. Watson: Overcoming PCB Designs Pitfalls

09-10-2020

When starting every PCB design, the hope is that we can navigate through any pitfalls that arrive. Unfortunately, many times, issues happen that you do not handle correctly; they fall through the cracks and end up in your PCB design. John Watson explains how that is when the real problems begin.

View Story

Elementary, Mr. Watson: How to Ruin Your PCB Design in 4 Easy Steps

08-06-2020

John Watson has seen firsthand how quickly PCB designs can “go off the rails” by not following a few simple principles. In this column, he looks at four practices that can easily ruin your PCB design.

View Story

Elementary, Mr. Watson: PCB Components Naming Conventions

07-09-2020

How you accurately analyze and identify certain information has a direct connection to the overall success of your PCB designs. In this column, John Watson focuses on the conventional naming scheme for the schematic symbol and footprint to prevent headaches and ulcers later.

View Story

Elementary, Mr. Watson: Collaboration in the PCB Design Process

06-11-2020

The past few months have been trying for everyone, with many of us working from home. However, there are still the underlining principles of collaboration to step into a role to finish the necessary tasks to keep a project moving forward. John Watson, CID, explains.

View Story

Elementary, Mr. Watson: Reinventing Yourself

05-28-2020

When COVID-19 first hit, many businesses were forced to close, and we immediately saw its impact on the service industry. Whatever challenge you’re facing, John Watson emphasizes that it’s time to hit the switch on reinventing.

View Story

Elementary, Mr. Watson: The Positive Side of COVID-19

04-16-2020

With the recent COVID-19 outbreak worldwide, most of us have been forced to reshuffle how we work, live, and play. Something like this has never happened before in our lifetimes, and it is scary and challenging, but difficult times develop resilient people. John Watson shares some of the positive things he has already noticed come out of this situation.

View Story

Elementary, Mr. Watson: Are We There Yet?

03-12-2020

Anyone who has taken a road trip with children knows the question, “Are we there yet?” very well. This question also applies to PCB design. If you are not careful, your PCB project could easily go off track and you could lose sight of what you are doing (objective), why (motivation), how (process), and when (schedule). John Watson emphasizes the importance of these fundamental questions.

View Story
Copyright © 2022 I-Connect007 | IPC Publishing Group Inc. All rights reserved.