An Area-Efficient Smart Temperature Sensor Based on a Fully Current Processing Error-Feedback Noise-Shaping SAR ADC in 180-nm CMOS
Antonio Aprile, Michele Folz, Daniele Gardino, P. Malcovati, Edoardo Bonizzoni
Abstract
This article presents a bipolar junction transistor (BJT)-based smart temperature sensor employing a noise-shaping successive-approximation-register (SAR) analog-to-digital converter (ADC). This approach, never explored before within a temperature sensing system, was chosen to exploit the low energy/conversion benefit peculiar to SAR-based solutions while overcoming their quantization-dominated resolution with an error-feedback technique. In addition, the system features a complete current-mode architecture enabling op-amp less signal processing and resulting in a highly compact design. Developed and fabricated in a standard 180-nm CMOS process, the sensor exhibits an active area of 0.057and draws a 34- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> A total current from a 1.8supply. Experimental results in the -50to 110sensing range demonstrate a 92resolution in a conversion time of 80 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> .