Power Management Case Study
How does a full-custom layout designer control the cost of constant innovation and iteration within a heterogeneous flow?
As green technology moves into the mainstream, an analog IC designer hustles to keep up with innovations in DC/DC converter controller technology. The goal: Allowing its customers to maintain low production costs and improve stability in microprocessor power supplies.
Getting to Thinner Notebooks
The designer’s customers look to it to develop smaller and more efficient power management components that go into computing, consumer, industrial and communication devices. A small power management footprint, for example, is important in trimming the profile of a notebook computer. Design teams work at reducing pin count and chip size to get higher performance in a smaller package for prominent ODMs.
In particular, DC/DC conver ter controllers make up a dynamic market. These designers are not on the same design for any more than two to three years at a time, because they must constantly come up with brand-new designs for their customers. They also need to cope with re-design and re-layout work when cost-saving measures result in moving production from foundry to foundry.
Optimizing Each Transistor
Full-custom layout design introduces a layer of almost constant iteration to the workflow of these designers. While the cost of this iteration can get out of hand, the company has built a business around iteration by keeping cost and performance under control when laying out by hand major portions of their designs and going from one design to the next. Their designs rarely stay the same, and they cannot use foundry-supplied standard cells. With analog designs at .18 micron and up, they create each transistor optimally because fully manual layout is often closer to artistry than to pushing simple polygons.
This culture of iteration is also part of the company’s goal of becoming the leading supplier of mixed signal semiconductors in the mobile computing and communications markets. Customers in those high-growth markets do not stand still, and they expect their IC suppliers to keep pace.
The company works in a heterogeneous flow to keep the cost of its investment in EDA tools low. L-Edit is easy on the software budget and integrates well with other high-end tools its teams use. Designers work first in a schematic capture tool, then hand off the drawn schematics to layout engineers who use L-Edit.
Later, for LVS, they use Calibre to check the layout produced by L-Edit against the netlist produced by schematic capture. As long as the transistor count in their chips stays below 10,000, they find that they are able to keep this heterogeneous flow relatively simple, without back-annotation or parasitic extraction.
"One very positive thing about L-Edit is its excellent integration with the Calibre verification tool we use," notes one design manager. They can load the Calibre DRC results database directly into layout and conveniently track down errors graphically. They can then click on an error within L-Edit, jump straight to that location in the layout and debug it.
In this regard, the world of physical design has the advantage of GDSII as a universally accepted format among tools. Tanner’s L-Edit supports this format completely.
Quick Path to Productivity
The company uses L-Edit with its extensive capabilities as the principal layout editing tool for all its full-custom design groups.
"L-Edit has always had a powerful set of keyboard and mouse shortcuts," notes another manager, and Tanner has put a lot of the design functionality into the mouse interface in the tool. L-Edit has a very mild learning curve, so we find that it doesn’t take much training for our designers to become productive. L-Edit operations allow you to accomplish more things with fewer keystrokes and less clicking and dragging.
"From long ago when I used other EDA tool suites, I remember that you could build very complex shortcut sequences with them. But L-Edit comes with a sensible set of shortcuts and mouse interaction by default. We didn’t need to configure or customize the tool because it did naturally what it was supposed to do as soon as we installed it."
The company is able to reuse existing designs easily–a technical advantage that translates directly into a business advantage in their environment of constant iteration. L-Edit allows them to import blocks easily from one design to the next, then edit and modify them.
The designers find that L-Edit is easier to use than other layout editing tools. Not only has Tanner made it easy to deploy L-Edit widely on many systems, but it has also kept the product affordable for the value and functionality packed into it.
"I have always been very impressed with the level of support that Tanner has given us," notes the director of engineering. “They have been very quick to respond and provide training when we’ve needed it.”