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NEC develops on-chip temperature sensor tech

Posted: 19 Jun 2008     Print Version  Bookmark and Share

Keywords:datacenter  temperature sensor  thermal distribution  LSI device 

Japan's NEC Corp. has made a possible breakthrough in the datacenter and related environments.

The company claims that it has developed an on-chip temperature sensor technology, which is said to ''visualise'' the thermal distribution levels in a device, thereby reducing power consumption.

The thermal sensor from NEC (Tokyo) is said to be one-tenth the size of previously available products. The sensors can be integrated in an LSI device. The on-chip devices are said to convert temperature changes into digital signals, enabling the heat distribution of an LSI device to be ''visualised'' in real-time, according to NEC.

The technology will result in better clock-frequency, data processing and voltage levels. In general, it will also deliver a 20-to-50 per cent reduction in the power consumption in LSI devices, said Masayuki Mizuno, senior manager for the Device Platform Research Laboratories within NEC's Central Research Labs.

On-chip sensors have already been demonstrated in NEC's SX-9 supercomputer. In that application, NEC has integrated 10 temperature sensors in a single central processing unit (CPU) in the SX-9, Mizuno said. The CPU within the SX-9 measures 19.84- x 21.04-mm. Each temperature sensor measures 35- x 35-um.

As a result, datacenter temperatures can now be regulated through continuous real-time monitoring, thereby lowering overall power consumption, he told EE Times.

NEC's thermal sensors could also appear in consumer gear, vehicles, networks and servers. NEC plans to announce the technology at the 2008 Symposium on VLSI Circuits, held in Hawaii from June 18-20.

The technology appears to be a breakthrough in the world of thermal or temperature sensors. Conventional diode-based thermal sensors are ''oversised and cumbersome,'' which prevented chips from being equipped with a large number of them. This inhibited a chip's ability to manage temperature levels, according to NEC.

NEC's thermal sensor technology is not a diode-based solution. Instead, it makes use of several technologies on the same device, including a current-to-digital converter and a temperature calibration unit with a single measurement function.

This in turn addresses and monitors another major problem in LSI designs: leakage current. Leakage currents in LSI designs could cause the lifetime of transistors and wiring to decrease by approximately 50 per cent.

One of the keys to NEC's technology is ability to ''visualise'' the thermal distribution levels within the device. ''Independent local measures can be taken on specific regions of an LSI chip in order to control heat,'' according to NEC.

''This allows tasks to be delegated to less active areas of a chip, which reduces the total amount of electricity required for operations and lessens the environmental impact,'' according to the company. ''The latest thermal sensors are able to calculate temperatures by measuring leakage currents from transistors through miniature conversion circuits that convert leakage currents to digital signals.''

A conversion equation has been developed to measure the volume of an active LSI's leakage current and to convert it into a temperature. Temperature miscalculations may be corrected through new technologies that take one measure of each thermal sensor's leakage current at room temperature, according to NEC.

''The latest sensors have been dramatically improved, and now provide temperature measurements that are within 3 degrees Celsius of accuracy,'' according to NEC.

- Mark LaPedus
EE Times

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