Abstract
CMOS temperature sensors have been used extensively in the computer-based applications. The accuracy level of a CMOS temperature sensor is limited by the temperature sensing device, circuit schemes and non-idealities such as mismatches in components, absolute variations and offset voltage in Op-amplifier. These factors usually affect the accuracy of sensors most. Accordingly, the accuracy level and non-idealities of typical voltage-base and current-base temperature sensors are analyzed in detail. This study provides guidelines for designing a high-accuracy temperature sensor. Based on these guidelines, a high-accuracy temperature sensor design is proposed. This design adopts second-order correction and piece-wise-linear techniques to reduce the error caused by the non-linear characteristics of a BJT device. Furthermore, dynamic offset-cancellation techniques are used to reduce the error caused by non-ideal factors in the sensor. By injecting 1% mismatch and 10% absolute variation in various components and 1mV Op-Amp offset voltage in the sensor, this temperature sensor has the best expected accuracy of 0.3°C from -55°C to 125°C. This result is sufficient to expand the applications of CMOS temperature sensors to high precision applications.