Cirrus Logic Case Study
How does a designer of precision, high-power ICs accommodate changing customer requirements quickly?
Apex Precision Power has built a business around custom IC requirements, which are the life-blood of this division of Cirrus Logic. The division’s success lies in implementing those requirements to existing and new designs on a tight schedule.
Apex designs ICs used in industrial, medical, aerospace, printing, measurement, and pick and place machinery. Their customers use the ICs in high-power, precise, analog products, such as pulse width modulation (PWM) amplifiers and power op-amps to drive brushless DC motors, piezoelectric drivers, programmable power supplies and other devices requiring high power (up to 50A and 1200V) and precision control.
Apex ICs also appear in control drivers for DC or 3-phase motors. The ICs deliver exactly the amount of power required to start and control the motors, whose internal drivers and small footprint make them one-of-a-kind products.
The Hard Part: Quick Turnaround
“Customers come to us and say, ‘I want to use your PWM amplifier, but I need more current delivery capacity,’” explains Design Engineer Priyank Gupta of Apex. “They may ask for one of our power op-amps, but with more slew rate or less output offset drift over temperature. Some customers need a greater operating voltage range, and we have to look into a different process and do a custom design. All of these requirements send us back to the drawing board to redesign and re-layout the ICs. In a hurry.”
Designers at Apex are always on a tight schedule because of the intensely competitive nature of their markets and their customers’ stringent requirements. With each new product, the designers leverage their expertise and parts of their existing work to come up with a unique solution for optimal time to market.
“Tight schedules require tools that can get us moving quickly, that everybody knows and that everybody can use. That's why we’re so keen on L-Edit. L-Edit is always going to be with us.”
So the facts of life at Apex are that the next design cycle is just around the corner, it’s going to be short, and the result will be another unique, niche product. Gupta and his colleagues need EDA tools that they can pick up and use right away.
The Designers’ Choice of Tools
All of the layout at Apex is custom work, so the team doesn’t use tools like automatic place-and-route. A small portion of the work is digital design, which they do by hand; it’s the predominance of analog work in the mixed-signal ICs that drives the need for custom layouts. The first tool Apex used was L-Edit, which they still use for all of their products. “Everybody here uses L-Edit for layout and verification tests,” says Gupta.
“It's easy to use, has strong features, facilitates debugging and has good DRC. We have HiPer Verify licenses as well, which make L-Edit compatible with Calibre formats, so it's a whole package in itself.
“L-Edit is intuitive a so whenever we have new layout designers come in, they can pick up and become productive right away. There's a very smooth learning curve to it, so our designers can focus more on doing the layout than on struggling with the tool.”
Tanner Tools enable Apex designers to meet the challenge of changing customer requirements, and emerge as reliable suppliers who meet their customers' deadlines and specifications.
They cite the portability of Windows®-based Tanner Tools, which frees them up to work remotely, a distinct advantage over Linux-/Unix-based tool sets. They also realize and appreciate the fact that they don’t need to spend hundreds of thousands of dollars on a line of EDA products.
Customized Foundry Requirements
Not every foundry can produce Apex’ unique designs, so the company works with the select few foundries in the world who have designed high-voltage cells and built in robust processes suitable for these ICs.
“Thanks to Tanner Tools, the results we get by testing fabricated ICs are very close to what we simulate on the software,” continues Gupta.
Generally the fab provides a Tanner kit with DRC rule sets and an extract definition file. If the foundry doesn’t have the kit for a certain tool, Tanner offers intuitive, sample verification files so that designers have a point of departure from which to write their own extract definition files and set up their DRC decks.
“We’ve found it easy to write DRCs in Tanner format based on what we find in the user documentation,” concludes Gupta.
“We can set up DRC decks using Tanner's L-Edit, which has a feature that enables us to set up derived layers and then set up good DRC checks. For a couple of our designs, we received DRC decks from the foundry, but we also had to create several of our own. With tools like Cadence, we have no idea what’s going on in the package, but there’s a lot of transparency, flexibility and excellent documentation with Tanner.”