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Method for a dual-diode thermometer

IP.com Disclosure Number: IPCOM000021740D
Publication Date: 2004-Feb-05
Document File: 2 page(s) / 38K

Publishing Venue

The IP.com Prior Art Database


Disclosed is a method for a dual-diode thermometer. Benefits include improved functionality,improved performance, and improved cost effectiveness.

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Method for a dual-diode thermometer

Disclosed is a method for a dual-diode thermometer. Benefits include improved functionality, improved performance, and improved cost effectiveness.


         Conventional thermal diode technology is limited by series resistance to the device. By placing all diode voltage comparisons near the diodes, series resistance is minimized to negligible values. Conventional thermal diode technology is sensitive to noise coupling from nearby signals.

         Equipment manufacturers and software developers use thermal diodes to control temperature by adjusting the fan speed. With processors, the series resistance of the thermal diode and noise issues arising from processor switching has led to challenges in measuring temperature reliably.

General description

         The dual-diode thermometer (DDT) utilizes two matched thermal diodes (substrate-connected positive-negative-positive transistors) co-located in silicon and excited by a pair of currents with a known ratio implemented through current mirrors. The difference in the diode voltage is independent of current variations shared by both currents and dependent on the current ratios. The differential voltage is proportional to the Kelvin temperature.

         The diodes are compared against a reference voltage provided to the silicon from an external source. The outputs of the two comparators are exclusively OR’ed (XOR), and the resulting logic signal is output. By varying the reference voltage and monitoring the logic output, an external measuring device can detect the temperature of the diodes.

         The disclosed method provides methodologies for incorporating multiple devices located throughout the die. By using trigger voltage levels on the reference input, each pair of diodes may be selected in a round-robin process without requiring extra input/output (I/O) pins.

         The thermal diode pins are shared with the DDT. By using a triggering method similar to the one used for selecting multiple devices, the DDT is enabled or disabled. By leaving the DDT disabled, an existing thermal diode may be used without requiring additional I/O pins.

         With the...