CPU Thermal Supervisor
April 2002
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Micrel Semiconductor (San Jose, CA) has developed a highly accurate, miniature two-zone thermal supervisor IC for thermal management using embedded thermal diodes such as those found in CPUs from Intel® and Advanced Micro Devices®, Xilinx® VIRTEX™ FPGAs, and other high-performance devices.

The MIC280 is part of a growing family of system and thermal management products from the company. Available in 6-pin SOT23 packaging, the MIC280 features highly accurate remote temperature measurement, six independent thresholds, I2C/SMBus® compatibility, a programmable interrupt output, and OTHER features that are said to enhance ease of use and system reliability.

"The main goals in developing the MIC280 were to offer a thermal supervisor with superior real-world accuracy, high reliability, increased programmer friendliness, a smaller footprint and lower cost," said Jim Judkins, product marketing manager. "The MIC280 fits into about one-fourth the space of legacy thermal supervisor ICs and offers far more features and performance.

"In many applications such as portable computing and telecom/datacom racks, the thermal envelope is very tight," Mr. Judkins continued. "This has fueled a drive toward more accurate thermal supervisors and led vendors to increase resolution and accuracy specifications. Specified accuracy on the datasheet can be very misleading, however.

"Users quickly learn that electrical noise from a system's high-performance digital circuits overwhelms everything else and destroys the accuracy they thought they had paid for. Micrel’s proprietary A-D converter, signal processing front-end, and one-wire diode interface give the MIC280 markedly superior noise performance in both laboratory and real-world testing. This translates directly into higher system accuracy."

Fault queues, programmable digital filters, are said to further enhance performance in noisy environments. Locking of critical functions, a serial bus timeout, reporting of diode faults, and independent over-temperature alarms enhance system reliability. Software ease-of-use features include the SMBus Alert Response Address protocol, programmable resolution, mask and status bits for all interrupt sources, S/W reset, and ID registers.

The MIC280's operating power supply current is 3 mA, and the quiescent current in shutdown mode is 5 µA. Eight different factory programmed slave address options are available.

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