Issue link: https://iconnect007.uberflip.com/i/1467185
MAY 2022 I DESIGN007 MAGAZINE 33 Shaughnessy: What other missing information or data do you find yourself having to "design around?" Thompson: PCB design is a hierarchy. As a designer, you start with what is known and ask relative questions about the unknowns you can foresee at the first customer meeting. You will start by reviewing the schematic so that you have an idea about power and part placement. Designers may have more questions when the design progresses. Speaking of power, power management ICs oen raise questions for the designer. A former boss of mine said of PMICs, "I had one instance where I was able to follow the reference/input very closely, and I thought it would be good, but it still needed some difficult work to get it right. Adding or moving caps and trying to squeeze more copper area or vias is oen not easy to do in crowded areas." ere is no shame in asking questions but try to catch as many of the relative questions in the first or second go-arounds. Customers don't appreciate an endless stream of questions and, more importantly, the resulting time lost for those additional questions. e only things you can "design around" are the non-essentials, like mask color or imped- ance calculations. ese things are done at layout and part placement occurs prior to lay- out. All stages of the design effort should have checks and balances, such as a part placement review by the end-user. Let's review the typical design process and see where these gaps can be filled in: 1. Kick-off meeting: Schedule a meeting with the customer to discuss variables. is is the first meeting, so having your ducks in a row is a must. Review the sche- matic and formulate questions regarding the expectations. is is the customer's first chance to share any specific concerns about the part or specific placement con- cerns. 2. Part placement review: is is the second opportunity for the customer to change part location or orientations prior to trace layout. Many times, the customer had for- gotten to tell the designer, or the designer did not ask in the kick-off meeting, and part placement changes must be made. 3. Final review of part/traces prior to exporting the final package to the end user: is is the final chance for the cus- tomer to make changes. Sometimes it gets all the way to the final review before it is realized that parts will have to change, due to availability, and a new schematic cre- ated. On a particularly tight design sched- ule, this may cause you some grief. On the topic of missing information, custom- ers invariably have some picture in their mind of what the layout should be. Not only do we have to divine what that is, via additional con- versations or other tools at our disposal, but we must balance that with our own knowledge of best practices for the given circuit and our customer's ideas on implementation. And then be able to create something that meets their expectations, even if it must be something dif- ferent than what they thought it would be. Some engineers hold everything close to the vest and divulge very little, but they should understand that a good designer can look at the parts list and schematic and tell what the product is, no matter how well the engineer conceals it. Remember the designer is your ally not your enemy. On the topic of missing information, customers invariably have some picture in their mind of what the layout should be.