Standard Analog IP?

MIPS adds mixed signal into its embedded IP at advanced process nodes, setting a new course in processors and its business model

MIPS Technologies is pushing integrated analog and digital IP on the same chip instead of using separate chips in the same package, reversing a trend set in motion by other major industry players two process nodes ago.

While most of the major chipmakers have internally reconciled themselves since then to integrating analog and digital on systems on a chip and custom ASICs, MIPS is the first major IP company to attempt this. Considered an integration migraine, because of the high noise levels generated by digital chips and the corresponding signal integrity fallout on the analog portion,many engineers predicted at the 90nm process node that problems would grow exponentially as they continued down the Moore’s Law road map. Ironically, those concerns actually have lessened at the 65nm and 45nm process nodes. Line widths continue to shrink, but corresponding drop in power and different buffering techniques have made integration of digital and analog far more feasible.

“All of the big companies are now going to integration of digital, analog and RF,” said Sergio Kusevitzky, vice president of the analog systems group at MIPS. “System in package is still in use, but mostly when it involves a collaboration of different companies or when companies have a strong digital component and they want to keep their mixed signal separate. They may have the same analog and change their digital technology every two or three years. And some companies are still afraid of full integration up front, so they’ ll start out with two chips to make sure there is enough demand and then integrate them in the second or third generation.”

Figure 1: Semiconductor Market

The reasoning behind this co-existence of technologies on a chip is the rapid proliferation of everything analog in consumer electronics. That explains why all the major EDA companies are racing to create analog toolsets that can provide some of the same benefits as digital toolsets. The problem, they say, is that analog processes tend to be much more customized, making it harder to create a suite of tools that meets the needs of a mass market. That gives analog designs a higher premium than digital, which is the reason that companies such as Texas Instruments have invested heavily in analog and why Linear Technology continues to trumpet the highest margins in the chip business.

Adding mixed signal into the embedded world was both a gamble and an obvious choice for MIPS, said Jack Browne, vice president of marketing for MIPS’ processor business group.

“There are four basic quadrants to an SoC (See Figure 2) and a couple of enabling technologies,” said Browne.

“There are the analog processor, DSP or data plane, control plane processor and embedded memory and libraries, along with the interconnect technologies and memory controller.”

He said a good portion of the real value for the processor is in the software. “The software is equal to or greater than the hardware, but because there is a large software community and ecosystem, that increases the competitiveness.

“That makes an analog component even more attractive for MIPS, because it is seen as a differentiator with enough standardized hooks to help companies speed designs to market. Ever since MIPS moved into the embedded processor IP world, it has been trying to grow from under the shadow of archrival ARM.

Browne said the audio codecs, as well as USB, timers and an RF front end are well-defined standards. “On top of that, the software we can create leverages the market and does not change very quickly. What MIPS is able to do is take two pieces that are market-defined standards and enable customers with a design methodology they’re already using.”

Noise-canceling technology

Reducing noise in mixed signal chip design enough to guarantee signal integrity has been a challenge for more than a decade. As late as 2003, National Semiconductor was predicting that mixed-signal chips were destined for the history books. A lot can happen in five years, though.All of the major EDA players now have a stake in the analog/ mixed signal (AMS) world. Cadence Design Systems developed its Incisive AMS verification platform and Synopsys has developed its Discovery AMS design and verification tools. Mentor Graphics has a simulation tool for AMS called ADVance MS, and Magma has its Titan platform for analog design that is not fully customized.

On top of that, foundries have developed better SPICE models. TSMC, UMC, Chartered Semiconductor and SMIC all are focused on ensuring that analog IP works. And MIPS has developed its own proprietary design rules for its IP that it considers a market advantage.

“We still believe everyone is going down the path that the person writing RTL code is living in a digital world,” Browne said. “But the bottom line is that the digital designers really don’t have to know analog that well; 50 percent of the power rails are still digital. What everyone is doing is creating enablers for the digital designers.

Diverging business models

From a business standpoint, MIPS’ acquisition of Chipidea Microelectronics last August marked a strategic shift in direction. It leaves ARM focused almost exclusively on the digital world— although ARM does have an analog timing product—and MIPS looking at opportunities in AMS. At the same time, the combined revenues of MIPS and Chipidea also moved MIPS into the No. 2 spot as a standard IP provider.

While the mixed signal market may look limited from the outside, MIPS believes the overallopportunity is huge. “The mixed signal market inside of companies like TI, Intel and Infineon is 7 to 10 times bigger than the free market, which consists of small and midsize companies,” said Kusevitzky.

MIPS estimates the analog merchant IP market at about $300 million. But with the proprietary market shifting to a more open approach because of the rising cost of investment necessary to create analog chips, that could be poised for significant growth, as well.

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