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Method for a self-calibrating thermal sensor

IP.com Disclosure Number: IPCOM000010228D
Publication Date: 2002-Nov-06
Document File: 3 page(s) / 81K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a self-calibrating thermal sensor. Benefits include improved functionality and an improved test environment.

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Method for a self-calibrating thermal sensor

Disclosed is a method for a self-calibrating thermal sensor. Benefits include improved functionality and an improved test environment.

Background

        � � � � � Conventionally, remote chipset temperature determination requires an expensive external component, motherboard space, and two pins. This solution is very sensitive to board layout.

        � � � � � A heat chamber is used to bring a thermal diode based internal thermal sensor to a known temperature. A resistor adjusts the current through this thermal sensor affecting the temperature coefficient slope. This reference temperature provides a single point to curve fit to the equation:� c – b*v = T, where T is temperature in degrees Celsius.

        � � � � � One problem with the conventional approach is that as the temperature deviates from the calibration temperature. The error in the temperature coefficient leads to larger prediction errors. Another problem with this approach is that the temperature of the heat chamber is only controlled to +/-3˚C. The comparator used to check the temperature trip point has a DC offset, which further adds to this error. The net effect is about a +/-5˚C error at the trimming temperature. Furthermore, this error increases as the real temperature deviates from the trimming temperature.

        � � � � � For successful self-burn-in, the requirement is a +/- 5˚C error at temperatures that are significantly distanced from the trimming temperature. Until a more accurate thermal sensor is found, implementing self-burn-in may not be practical.

        � � � � � Another temperature error contribution with the conventional approach is that a thermal sensor is used at only one location rather than multiple places on the die. Multiple thermal sensors are required on the die when more than one hot spot occurs.

        � � � � � The conventional method’s test time is significant because the test must be done relatively slowly to ensure that the transients settle.

        � � � � � Conventionally, the thermal sensor error is such that the thermal limit error guardbanding drastically impacts chipset performance.

General description

        � � � � � The disclosed method is a self-calibrating thermal sensor. The method includes two A/D converters. A 7-bit A/D converter leads to about a +/-3˚C temperature error over the entire 0-100˚C temperature range. An 8-bit A/D converter leads to about a +/-1.5˚C error without trimming for the same area as the current solution.

        � � � � � The disclosed method is easily adapted to measuring temperature at multiple die locat...