Precision Temperature Sensors In Cmos Technology

Precision Temperature Sensors in CMOS Technology

The low cost and direct digital output of CMOS smart temperature sensors are important advantages compared to conventional temperature sensors. This book addresses the main problem that nevertheless prevents widespread - plication of CMOS smart temperature sensors: their relatively poor absolute accuracy. Several new techniques are introduced to improve this accuracy. The effectiveness of these techniques is demonstrated using three prototypes. ? The ?nal prototype achieves an inaccuracy of±0.1 C over the military t- perature range, which is a signi?cant improvement in the state of the art. Since smart temperature sensors have been the subject of academic and industrial research for more than two decades, an overview of existing knowledge and techniques is also provided throughout the book. Inthisintroductorychapter,themotivationandobjectivesofthisworkare- scribed. ThisisfollowedbyareviewofthebasicoperatingprinciplesofCMOS smart temperature sensors, and a brief overview of previous work. The ch- lenges are then described that need to be met in order to improve the accuracy of CMOS smart temperature sensors while maintaining their cost advantage. Finally, the structure of the rest of the book is introduced.

Precision Temperature Sensors in CMOS Technology

Energy-Efficient Smart Temperature Sensors in CMOS Technology

This book describes the design and implementation of energy-efficient smart (digital output) temperature sensors in CMOS technology. To accomplish this, a new readout topology, namely the zoom-ADC, is presented. It combines a coarse SAR-ADC with a fine Sigma-Delta (SD) ADC. The digital result obtained from the coarse ADC is used to set the reference levels of the SD-ADC, thereby zooming its full-scale range into a small region around the input signal. This technique considerably reduces the SD-ADC’s full-scale range, and notably relaxes the number of clock cycles needed for a given resolution, as well as the DC-gain and swing of the loop-filter. Both conversion time and power-efficiency can be improved, which results in a substantial improvement in energy-efficiency. Two BJT-based sensor prototypes based on 1st-order and 2nd-order zoom-ADCs are presented. They both achieve inaccuracies of less than ±0.2°C over the military temperature range (-55°C to 125°C). A prototype capable of sensing temperatures up to 200°C is also presented. As an alternative to BJTs, sensors based on dynamic threshold MOSTs (DTMOSTs) are also presented. It is shown that DTMOSTs are capable of achieving low inaccuracy (±0.4°C over the military temperature range) as well as sub-1V operation, making them well suited for use in modern CMOS processes.