Thermal uprating of a mixed signal microcontroller

Thermal uprating is the process of component evaluation for functionality, performance and/or reliability requirements of the application in which the component is used outside the operating temperature range specified by manufacturer. The uprating is performed when designer cannot find an appropriate component on the market, such as in high-temperature electronics applications. Downhole instrumentation for oil-well logging requires high-resolution analog-to-digital converters (ADC) operating at temperatures up to 200 /spl deg/C. In this study, we evaluate high-temperature applicability of a 16-bit single-slope ADC embedded in mixed signal microcontroller (PIC 14000, microchip) specified for operation in industrial temperature range. Described uprating includes functionality and performance evaluation (linearity of transfer function) at temperatures up to 175 /spl deg/C. We have used an NP0 ceramics external capacitor for the measurements. Our results showed ADC linearity error of 0.024% (12-bit resolution) at 25 /spl deg/C, 0.058% (10-bit resolution) at 125 /spl deg/C and 1.45% at 175 /spl deg/C (6-bit resolution).