Faster Board Speeds Demand Constraint-Driven Design


Reading time ( words)

Do you still use Post-it Notes? Invented in 1979, this simple, yet incredibly powerful communication mechanism is still commonly found in engineering and design departments. Despite modern electronic communication, many companies still struggle to provide a replacement for their ease-of-use and versatility.

But, by changing the way an engineer designs electronics, by giving up the Post-it for passing requirements, change requests and constraints between engineers, design times can be shortened and product quality improved. Modern PCB design tools permit the definition of design constraints, including constraints relating to high-speed design and EMC, such as the topology of connections (routing pin sequence) or overshoot and timing budgets, for example.

These constraints become increasingly important as components and boards become faster and more complex. But it is hard to capture and use/obey these constraints consistently throughout the complete design process, bearing in mind that may contradict each other. The Post-it Note captures this idea particularly well. A brief sketch implicitly includes the constraints that the designer is working under, in a very concise form; however retaining and using this information later is extremely difficult.

Adaptive Design

Using these powerful constraint techniques can be a double-edged sword. While the design process is made much safer by including constraints, it is all too easy to over-constrain the design and make it impossible to complete routing and placement. Even paper design guidelines can make products uneconomic to produce unless a great deal of engineering knowledge is applied during the design. This means the design tool has to be adaptive—reacting to changes in the design as it progresses. Combining these elements is anything but trivial, but doing so allows the designer to converge on the optimum design in the first pass, rather than via multiple attempts.

In PCB design, attributes (or constraints) and rules have always existed, and designers have tried to achieve their design goals, especially with systems that are based around the raw attributes of the components in a design. But attributes (or properties) are essentially just data about the pins, components or tracking, while constraints are requirements that must be obeyed. Examples include the maximum delay, or an error marker, which must be flagged as functional or an operation may be at risk. These can simply be a function of the design attributes, but constraints are typically more complex nowadays and they sometimes relate to each other (e.g., in high-speed memory the relationship between the byte lanes and from the data/address signals to strobe and clock signals). Constraints must exist through the different stages of the design process, from schematic to placement to routing.

To read this entire article, which appeared in the May 2018 issue of Design007 Magazine, click here.

Share


Suggested Items

Fully Automated Schematic Verification

02/05/2018 | Craig Armenti, Mentor
Schematic verification is a part of the hardware engineer’s responsibility just as PCB layout verification is an accepted part of the PCB designer’s responsibility. However, with today’s circuit designs becoming more and more complex, time-consuming manual schematic verification is no longer an option. Manual verification of a complex circuit introduces significant risk by not identifying schematic design errors that are, in turn, passed to the downstream processes and ultimately to the fabricated board.

Nano Dimension’s 3D Printing: Prototypes at the Push of a Button?

01/26/2018 | Barry Matties, Publisher, I-Connect007
SICK AG is a global manufacturer of sensors and sensor solutions for industrial applications, with headquarters located in Waldkirch, Germany. After a demo of Nano Dimension’s new 3D printing machine at productronica, Barry Matties met with SICK’s Danny Wernet to discuss its pros and cons and get his overall impression of the technology. Are 3D prototypes really as simple as feeding in a Gerber file and pushing a button?

Bay Area Circuits Updates InstantDFM Tool

11/29/2017 | Andy Shaughnessy, PCB Design007
Bay Area Circuits is on a quest to help PCB designers and design engineers. For the past few years, the company has been holding facility tours and open house events to help designers understand more about the fabrication process. Now, Bay Area Circuits has upgraded its free design tool, InstantDFM.com, which allows customers and non-customers alike to check manufacturability and request pricing of their jobs. At PCB West, Andy Shaughnessy spoke with President Stephen Garcia and COO Brian Paper about the new tool update, and some of the other services they offer for PCB designers.



Copyright © 2018 I-Connect007. All rights reserved.