Evaluating PCB layout tools: A board developer’s perspective
Cadence Allegro:
Allegro is one of the oldest and the most diversified tools in the industry. No one can question the power it gives to the designer to tweak every aspect of the layout. It also has one of the best constraints managers that give better control on signal and power integrity of the board. Figure 1 below shows how detailed and comprehensive its constraint manager is.
Figure 1: Allegro’s Constraint manager at a glance (To view larger image, click here).
It is also the best tool to handle a large number of board layers. Ever since Cadence bought OrCad, their developers have tried to integrate the two. Therefore, one will find that Cadence OrCad for schematic capture is integrated to a certain extent with Allegro for layout. Figure 2 below shows cross-Probing being done between Cadence OrCad and Allegro.
Figure 2: Cross-Probing done between Cadence OrCad & Allegro (To view larger image, click here.)
Allegro PCB SI and OrCad Signal Explorer help to do a pre- and post-layout signal integrity analysis and are efficient at doing this for complex PCBs. Allegro also provides a much better integration to Allegro PCB router, formerly known as Cadence SPECCTRA, than any other layout tool. SPECCTRA is one of the most well known products used for Auto-routing.
However, Allegro is not without its drawbacks and limitations. Most importantly is its cost. A Cadence seat along with a suite that can handle almost all design needs can cost upwards of $90K. Spending this amount on a layout tool by a mid-sized company or start up OEMs does not seem plausible and would be the deciding factor for most.
Secondly, Cadence tools are sometimes too complicated and cryptic to understand. The GUI is not intuitive or user friendly. Many functions are hidden deep within the tool and many easy tasks are difficult to carry out. Moreover, Allegro part libraries are difficult to create and maintain.
Thirdly, Cadence has a tortuous file structure that is awkward to manage. Generating outputs for manufacturing can become an arduous task in Allegro. As an example, PCB designer has to go through numerous steps in specific order to setup and generate drill files and Gerbers.
Also, this tool is not effective at handling multiple copper fills for power and ground planes. Designers have to work diligently while dealing with static and dynamic shapes and suffice to say that handling numerous copper shapes in Allegro is not a walk in the park and can become too laborious for some.
Finally, Cadence Allegro is notorious for the use of its scripts and macros to perform fairly basic tasks that could be performed fairly automatically in other layout tools.
Loading comments... Write a comment