Analog Simulation Insights


More on analog synthesis and the non-cognoscenti

I received some good comments to my previous post (… Because digital design is so easy!) from Rich at Silicon Canvas, which I would like to follow up on. I get pretty passionate about this topic, and my reply to him was getting so long that I think it is better to place it here as a separate post.

Rich points out that overall analog design productivity has improved substantially due to advances in EDA tools, with schematic-driven layout as a prime example. I couldn’t agree more! Schematic-driven layout (SDL) is a great example of the productivity improvements brought about by analog EDA. I just wish I had SDL when I was designing my IC layouts by pushing polygons. (No.. I never actually had to cut rubylith!)

One key point I am trying to make though, is that EDA-enabled analog synthesis IS here, if you just understand that the process of implementing an analog design is fundamentally different than digital design. All the NC (Non-Cognoscenti) pundits don’t seem to get that.

The critics can only think of tools like Design Compiler. Digital synthesis maps RTL and gates to cells in a library. I could just as easily argue that digital synthesis is not REALLY synthesis, because someone had to design the cell library at the transistor level. Hmmm… designing the transistors… now that sounds familiar! I have yet to look at a chip photomicrograph and see a single line of RTL code… have you?

When I was architecting our synthesis methodology at Antrim, this was my starting point and our motto… do not compare analog synthesis to digital, because there is no Boolean algebra for analog. The philosophy I followed was to look at what analog designers do, find ways to make it more repeatable and reusable, while automating the most tedious tasks. Prior art at the time was mostly made up of academic attempts to create analog design compilers for Op-Amps… not particularly useful. Thinking of the solution without first asking what the problem is is not a recipe for success.

Analog EDA is the field of developing tools to increase analog designer productivity. Thinking of synthesis in terms of compilation does not equal finished silicon, for analog or digital designs. Ultimately it’s all about the transistors, and the flows to get there for analog and digital designs are necessarily different.


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