Mixed Signal: Why The Sudden Attention?

With DAC 2010 rapidly approaching, we can again expect that lots of EDA and IP vendors will use “mixed signal” somewhere in their company’s messaging. Last year it seemed that nearly everyone wanted to jump on the mixed signal “bandwagon” … so what caused this sudden jump in interest in mixed signal?

We all know that mixed signal design is not new. It’s been around for about 20 years (give or take), but there has been a shift in the types of mixed signal designs that are being developed.

In the past, a mixed signal design was typically a pretty small design that was created using a manually-driven design methodology. Design engineers drew schematics and simulated the design, while layout designers created the physical layout based on the schematics and constraints from the design engineers. Custom schematic editing and layout tools such as Virtuoso were used for these designs.

As the digital content of these mixed signal designs grew beyond a manageable number of instances, a purely manual implementation approach rapidly became a major bottleneck. Instead, design teams looked to more automated digital implementation solutions, based on standard ASIC methodology. Here at Cadence, we created a specific product for such designs, called Virtuoso Digital Implementation (known as VDI), which complements Virtuoso and enables automatic digital implementation for up to 50K instances. VDI has seen rapid growth, which reflects the growth in these types of mixed signal designs.

In the past couple of years, there have been a growing number of mixed signal System on Chip (SoC) designs … very large, very complex designs that contain multiple digital and analog components fully distributed throughout the chip. A simple example of such a design is shown in Figure 1.

Figure 1: Example mixed signal SoC design

There are many additional design and methodology challenges associated with developing this type of advanced mixed signal SoC chip, mostly related to size and functional complexity. It all starts with early functional verification, where simulators are challenged to simulate huge netlists over large timescales in order to comprehensively validate that the design meets the functional specification. The challenges continue through physical floorplanning, analog/digital/mixed signal implementation and eventually design signoff prior to tapeout.

Large designs mean that power management is critical, while fully distributed analog and digital components force attention to noise management. The advanced process technology, required to enable such large amounts of functionality to be integrated onto the same die, forces even more attention on design for manufacturing techniques, else low yields can be expected.

These design challenges, plus industry predictions that practically every design will be a mixed signal design in the not-too-distant future, are gaining attention for obvious reasons.

Cadence has already focused on all components within our mixed signal design flows to ensure that such complex SoC designs can be efficiently designed. If you are going to DAC, stop by our booth (#1334 in Hall B) and learn why the EDA industry is positioning Cadence as a true leader in mixed signal.

Pete McCrorie