Designs and develops analog-intensive, mixed-signal integrated circuits for a range of applications

Latest project: Mixed-signal 85-MHz design of approximately 100,000 gates for cell phone radio IC in a TSMC 130-nm standard CMOS process. The team used "a fairly standard ASIC flow."

Design team: 22 people

Design tools: Matlab, Elanix System View, Cadence Composer/Virtuoso, Mentor Graphics Calibre. Synopsys tools including Power Compiler, AstroRail, PrimeTime, StarRC, TetraMax. Analog design was simulated in Cadence's Spectre RF and verification used the Verilog-AMS language.

When Silicon Laboratories Inc. formed a design team in early 2004 to create a radio tuner IC, the company knew that power consumption would be its biggest challenge. The goal was to create a small FM tuner IC, giving cellular handset users the option of listening to stereo-quality radio on their phones. The goal was achieved, with the Si470x shipping recently as the first FM tuner IC in CMOS.

Targeted at a TSMC 0.13-micron standard process, the mixed-signal design included low-noise amplifiers and 15-bit resolution A/D converters. The team optimized the DSP to deliver the needed MIPS at 85 MHz.

Tyson Tuttle, the leader of the 20-person design team, said, "We were pushing power and had to work on the models for noise and device matching. We had good models, but our plan was to run this below the rated voltage (1.2 V) for the process. We had to do a lot of hand work, and make some assumptions, to figure out how fast the transistors ran at various voltages (below the rated voltage)."

The result was a chip with about 100,000 gates, running at 0.85 V for the digital blocks and 2.7 V to 5.5 V for the analog transistors.

"To create the VCOs [voltage-controlled oscillators], the mixers, the A/D and D/A converters, we needed very precise models," Tuttle said. "And we had to make trade-offs at the architectural and system levels to optimize for power, because this chip was aimed at battery-operated systems."

One challenge for designers, he said, is that digital complexity is growing fast. Tuttle said, "The guy drawing the block diagram can add functions, but to the people designing the chip, that added complexity must be compensated for with higher productivity from the tools."

The goal: a small FM tuner IC with power kept in check.