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Volume 11 (Oct 22, 2003)
Introduction of VLSI Symposia Presentation Papers (2/2)
Circuit Symposium
3Gbps, 5000ppm Spread Spectrum SerDes PHY with Frequency-Tracking Phase Interpolator for Serial ATA
Serial AT Attachments are used in servers and other products as an interface standard that enables the realization of high-speed data transfer between computers and hard disc drives (HDDs). However, the reduction of electromagnetic radiation noise in devices has become an important issue to be addressed, and the use of a spread spectrum that modulates clock frequency is expected to provide a solution to this problem.
As for its 3Gbps Serial ATA, NEC Electronics has developed a transceiver and receiver circuit that actualizes a spread spectrum with a frequency modulation rate of 0.5%. This circuit includes a spread spectrum carrier generator that modulates clock frequency and a clock and data recovery circuit that generates clock and data as well as tracks the data that modulates the frequency through the spread spectrum. And since the phase interpolator is self-running, a reduction in power consumption of 6mW per channel and a 10% decrease in size to macrosize were actualized. Thus, this technology is particularly effective for servers that require multichannel structures.
The test chip NEC Electronics presented at the symposium was an 8-channel Serial ATA fabricated using the 0.15µm, 1.5V CMOS process. The photo shown here is of the physical layer of the chip (Photo 1). The spread spectrum carrier generator is included in the common block, while the clock and data recovery circuit is included in each of the channel blocks (CH1 to CH8). Measurement results have confirmed a decrease in the spectrum peak level of the clock and verified a reduction in radiation noise.
A Non-uniformity Correction Scheme using Multiple Analog Bus for an Uncooled Infrared Sensor
In addition to being capable of measuring the temperature of objects without physical contact, infrared cameras can also capture images in the dark. For this reason, infrared cameras can be used in a wide range of applications, including transformer maintenance devices, fire detection equipment, crime prevention systems, intelligent transport systems (ITS) and medical care products (Photo 2). In a joint development effort with NEC, NEC Electronics succeeded in developing a circuit technologythat is able to correct the non-uniformity among the infrared detectors and achieve both highly sensitive and stable operation.
With conventional correction technology, circuit area and power consumption had to be increased because it was necessary to install a current source and A/D converter for correction in each channel. Through use of this new technology, however, it is no longer necessary to install current sources or A/D converters, and non-uniformity problems in the infrared sensors and also various types of LSI devices can be solved.
The sensor presented at the VLSI Symposium has readout circuits and detectors on the same chip. The detector is suspended in the space by a narrow beam to keep thermal energy, and there are approximately 80,000 detectors on the chip. The thermal energy is converted into electrical signals by the detector (Figure 3). Although the 160 readout channels amplify the electrical signals from the detector, if the resistance non-uniformity of the 80,000-pixel detector is large, gain of the amplifier cannot be increased. The solution to this problem lies in the newly developed non-uniformity correction analog bus (Figure 4). This non-uniformity correction analog bus has 16 wires with differing analog voltages on the readout channels, therefore supplying 16 levels of analog voltages to the readout channels. Each of the readout channels has a selection switch, and depending on the non-uniformities of the detector, one of the 16 voltage levels can be selected and added to the detector. By having two different analog buses, it is possible to reduce the effects of detector non-uniformities by as much as 1/256.
* Synopsys is a registered trademark of Synopsys, Inc. Star-RCXT is a trademark of Synopsys, Inc. Columbus is a registered trademark of Sequence Design, Inc. All other companies and product names mentioned on this page are trademarks or registered trademarks of their respective owners.
