Back in 2002 and 2003 there was a lot of talk about analog
synthesis being the "next new thing" to close the productivity gap between
analog and digital designers. Well, I hope you didn't hold your breath for this!
That promise failed mostly because analog design was still a
custom design challenge, relying on innovation to provide differentiation in
the final application. Standardizing analog design, or constraining the design
to a fixed set of rules, never worked in reality, and innovation was squashed in
Also, new designs are typically bigger, better and faster
than previous generations, and a fully automated solution provides little more
than derivatives of what already exists (assuming these derivatives work).
However, the challenge never went away, and over the past
seven years there have been a number of different approaches to try and move
analog design out of the critical path. These seem to focus mostly on offering
premade IP or speeding up the core verification tools used, such as simulation,
extraction and DRC/LVS.
For custom design to be truly effective and productive,
these improvements are certainly needed, but a number of additional
capabilities are necessary to facilitate the innovation of the designer. The
answer lies in "Assisted Design," which I like to think of as analogous to
adding power steering to your design flow. The designer is left in control, but
the effort to move a design from point A to point B is reduced. Here,
automation has a part to play and can be used to augment the flow, without
There are a number of capabilities that fit into this space
that support the "power assisted" flow, some of which you may already be using.
I'll introduce them here and in future blogs I'll go into more detail. If there
is a topic in this area you want covered, let me know.
Sweeps and Tuning
This is a commonly used tool that can simply vary the design,
assess the impact on the design goals, and manually find the optimum solution.
Early in the design creation process, feasibility analysis
can be used to quickly see if a design has potential before more extensive
investment in simulation is made.
For any design solution, it's possible to quickly explore
the design's sensitivity to processing variability and environmental conditions
and even the sizes of the devices used in the design.
This involves pulling a design into compliance over all the
required conditions, and can be quite time consuming where a large numbers of
corners are concerned.
Understanding the manufacturing margin is becoming more
critical as greater performance is being demanded from existing foundry
processes. For some applications, high-yielding designs up to six sigma margins
The performance of the final implementation can be quite
different from the idealized view presented in a schematic. The earlier the
layout effects can be assessed, the less iterations are needed between the
electrical designer and layout designer.
Design Constraints (not to be confused with Design Rules)
As we know them, design rules are actually process rules and
can also be sometimes called constraints. Here, I am referring to
the implementation requirements that are specific to a design's
Documentation is often left until the last minute, but is
still required to sign off a design.
Automation in the custom design flow often leaves designers
worried over loss of control or concerned over wasting a lot of time. Future
blogs will explore how automation technology can be embraced in a practical
flow that supports the designer's creative process and assists in meeting
With the ability to do floor planning and the advanced placers and routers available already in the cadence environment, it seems that we can take a page out of the digital design to get a better picture of what the design would be like by running the analog design through a trial place/route phase and access routing information for parasitic analysis earlier in the design cycle. It may not be the final numbers, but like encounter it gives valuable information and makes the finished product better. True it may make some incorrect assumptions, but having a better picture earlier in the design process would I believe greatly reduce the design cycle.