Renesas Electronics Announces Development of On-Chip Inductor Technology with a Wide Inductance Variability

TOKYO, Japan, June 23, 2010 — Renesas Electronics Corporation (TSE: 6723) today announced the successful demonstration of variable inductor technology that has a wide tuning range for inductance with small degradation of the Q-factor values. The degradation level of an inductor (coil) using the new technology exhibits 50 percent smaller than those of existing technologies. Applying this newly developed technology, Renesas Technology has also designed an ultra-wide frequency range tunable oscillator using this on-chip inductor and has verified its basic operation.

Recently, AV equipment and PCs often include a variety of high-speed data communicating interfaces that operate over gigabit per second (Gbps). These interfaces require many large passive devices including inductors and capacitors to realize high-speed circuit operation, such as clock generation. Although it would be desirable to vary the values of these inductors and capacitors over wide ranges to comply with a variety of communications standards, it has been especially difficult to vary the values of an on-chip inductor. While methods for varying inductance by changing the connection among multiple inductors with transistor switches or mechanically moving a magnetic material have been proposed, with the former method, the resistance of the transistors used for switching drastically degraded the inductor's characteristics (Q-factor values), and with the latter method, it was difficult to integrate the inductors on silicon chips.

In the circuit developed based on Renesas Electronics' new technology, four inductors are connected in a bridge structure with two pairs of inductors each connected in parallel. The inductance value of this circuit can be varied over a wide range by moving the electrical balance point of this bridge circuit with a transistor switch. This design makes it possible to reduce the degradation of inductor performances even when the inductances are varied.

For example, measurements on the prototype of the newly developed variable inductor showed that the degradation level of the Q-factor value was reduced by approximately 50 percent compared to existing technologies. Renesas Electronics also developed a prototype frequency oscillator using this variable inductor and achieved a wide frequency band operation over 10 to 20 GHz range.

Renesas Electronics believes that the new technology will contribute to realizing more compact analog and RF circuits, as well as high-speed circuits that use large numbers of passive devices, with improved performances, and will continue to advance its research and development activities in this area.

Renesas Electronics presented the results of this research at the Symposium on VLSI Circuits, which was held in Honolulu, Hawaii from June 16 to June 18.

About Renesas Electronics Corporation

Renesas Electronics Corporation (TSE: 6723) delivers trusted embedded design innovation with complete semiconductor solutions that enable billions of connected, intelligent devices to enhance the way people work and live. A global leader in microcontrollers, analog, power and SoC products, Renesas provides comprehensive solutions for a broad range of automotive, industrial, infrastructure, and IoT applications that help shape a limitless future. Learn more at renesas.com. Follow us on LinkedIn, Facebook, Twitter, and YouTube.

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