AN 769: Intel FPGA Remote Temperature Sensing Diode Implementation Guide

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ID 683139
Date 4/06/2022
Public
Document Table of Contents
Document Table of Contents x
1. Introduction 2. Implementation Overview 3. Implementation Consideration 4. Evaluation Results 5. Conclusion 6. Document Revision History for AN 769: Intel FPGA Remote Temperature Sensing Diode Implementation Guide
3. Implementation Consideration x
3.1. Ideality Factor (η-Factor) Mismatch 3.2. Series Resistance Error 3.3. Temperature Diode Beta Variation 3.4. Differential Input Capacitor 3.5. Offset Compensation
4. Evaluation Results x
4.1. Evaluation with Maxim Integrated* 's MAX31730 Temperature Sensing Chip Evaluation Board 4.2. Evaluation with Texas Instruments* 's TMP468 Temperature Sensing Chip Evaluation Board
1. Introduction
2. Implementation Overview
3. Implementation Consideration
4. Evaluation Results
5. Conclusion
6. Document Revision History for AN 769: Intel FPGA Remote Temperature Sensing Diode Implementation Guide

3.5. Offset Compensation

Multiple factors can simultaneously contribute to the measurement error. Sometime, applying a single compensation method may not fully resolve the issue. Another method to resolve the measurement error is to apply offset compensation.
Note: Intel recommends that you use a temperature sensing chip with built-in offset compensation. If the temperature sensing chip does not support the feature, you may apply offset compensation during post processing through custom logic or software.

Offset compensation changes the offset register value from the temperature sensing chip to eliminate the calculated error. To use this feature, you must perform a temperature profile study and identify the offset value to apply.

You must collect temperature measurements across the desired temperature range with the default settings of the temperature sensing chip. Afterward, perform data analysis as in the following example to determine the offset value to apply. Intel recommends that you test several temperature sensing chips with several remote temperature diode to ensure that you cover the part-to-part variations. Then, use the measurements average in the analysis to determine the settings to apply.

You can select the temperature points to test based on your system operation condition.

Equation 5. Offset Factor

Application of Offset Compensation

In this example, a set of temperature measurements was collected with three temperature points. Apply Equation 5 to the values and calculate the offset factor.

Table 1.  Data Collected Before Applying Offset Compensation
Set Temperature Measured Temperature
100°C 373.15 K 111.06°C 384.21 K
50°C 323.15 K 61.38°C 334.53 K
0°C 273.15 K 11.31°C 284.46 K

Use the middle point of the temperature range to calculate the offset temperature. In this example, the middle point is the 50°C set temperature.

Apply the offset temperature value and other compensation factors, if required, into the temperature sensing chip and retake the measurement.

Table 2.  Data Collected After Applying Offset Compensation
Set Temperature Measured Temperature Error
100°C 101.06°C 1.06°C
50°C 50.13°C 0.13°C
0°C 0.25°C 0.25°C
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