CMOS oscillator said to beat quartz


R. Colin Johnson

PORTLAND, Ore.— Integrated Device Technology Inc. has introduced what it claims is the world's most accurate all-silicon CMOS oscillator with the industry's highest frequency accuracy, measured in parts per million (ppm).

Synchronizing high-speed digital circuitry needs rock-solid time bases, which usually means quartz-crystal based oscillators. CMOS oscillator makers, however, claim to be pioneering a new breed of digital time bases that are faster than quartz crystals yet smaller and lower power than MEMS.

"We are launching a 100 ppm all-CMOS oscillator that makes us competitive with crystal oscillators," said Michael McCorquodale, founder of Mobius Microsystems which invented the all-CMOS oscillator technology acquired by IDT (San Jose, Calif.) earlier this year. At IDT, McCorquodale is general manager of the Silicon Frequency Control (SFC) business. "We have already shipped 3.2 million units just in the last quarter."

IDT is promising 50 ppm parts by 2011, but has been quietly seeding OEMs with advance models of its current 100 ppm IDT3C02 oscillator, which is already replacing quartz crystals in a wide variety of timing applications. IDT claims design wins for Gbit Ethernet, Display Port clock, subscriber identity module (SIM) card, encryption token key, smart-card, microcontroller reference, peripheral component interconnect express (PCIe), serial advanced technology attachment (SATA), solid-state drive (SSD), universal serial bus (USB 3.0), flash drives and card readers.

Early reports from OEMS, according to IDT, claim that their digital circuits are achieving superior bit-error rates with its IDT3C02 despite its lower cost over quartz crystals and tiny 5-by-3.2-by-0.9 millimeter size (with an even smaller footprint--2.5-by-2-by-0.9 millimeter—planned for its 50 ppm part due out in 2011).

IDT3C02 oscillator (on top) can be wirebonded to the OEMs application specific integrated circuit (ASIC, on bottom)

"We have put the right compensation circuitry on our all-silicon CMOS oscillator to generate very high frequencies with good accuracy," said Tunc Cenger, senior manager of product marketing at IDT. "And our added value is that you can integrate inside the package which you can't do with quartz."

IDT delivers its all-silicon CMOS oscillators on wafers before dicing, so that its customers can stack the IDT3C02 on top of their application specific integrated circuit (ASIC) in a multi-chip package, or for ultra-price-sensitive applications, like flash drives, OEMs can affix the IDT die to a chip-on-board (CoB).

IDT has 35 issued and pending patents on its unique compensation circuitry and die encapsulation that hermetically seals its CMOS oscillator to protect it from stray electrical fields and changes in the environment, such as humidity, that had prevented previous designs from achieving 100 ppm frequency accuracy and less than 457 femtosecond phase jitter.

The frequency-trimmed, temperature-compensated, environmentally-stabilized IDT3C02 achieves -140dBc/Hz phase noise by beginning with a 3GHz self-referenced LC oscillator that it divides down to user-programmable range of from 4-to-133MHz. By using no power-consuming phases locked loop (PLL), the the IDT3C02 consumes less than a quarter of the power required by quartz, MEMS and other all-CMOS oscillators--just two milliamps active and 200 nanoamps in stand-by with 100 microsecond start-up--plus can run at any supply voltage from 1.8-to-3.3 volts. The no-moving-parts design, compared to quartz or MEMS, also leads IDT to claim superior shock and vibration resistance for its all-silicon CMOS approach.

IDT mixed signal die for its all-silicon CMOS oscillator houses a large inductor (top) surrounded by its compensation circuitry

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