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This paper presents a co-design of a 10-bit SAR ADC and its front-end filter. Because the SAR ADC works as a discrete-time data converter, its input signal only needs to be accurate at its sampling moment. Therefore, the filter can be switched off in the ADC conversion phase to save power. To reduce the start-up time when the filter is activated again, a low-power auxiliary amplifier is used in the ADC conversion phase to maintain the filter output roughly. A 10-bit 10 MS/s SAR ADC with such a duty-cycled multiple feedback filter is fabricated in a 65 nm CMOS technology. The filter power has been reduced by 36% thanks to the proposed duty-cycled operation. The prototype achieves 8.3 ENOB and 59.3 dB SFDR at low input frequencies, and it has 40 dB suppression at the Nyquist input frequency, while consuming 91.1 µ W.

This letter presents a dynamic resistive temperature sensor for IoT ambient temperature monitoring applications. The sensor integrates on-chip analog offset, gain, and nonlinearity correction techniques with state-of-the-art power and size performance. By shifting the reset phase of the ADC, analog offset correction is realized. By adding programmable capacitors, gain errors are corrected. By presetting and resetting a small capacitor array, the systematic nonlinearity error is mitigated. A piecewise linear approximation is adopted to reduce overhead. The temperature sensor achieves +0.7°C/-0.6°C accuracy with 2.98 pJ/conversion and 0.0023 mm2, including all corrections, resulting in a resolution FoM of 0.66 pJ K2.

This paper reviews several examples of ultra low power sensor interfaces for IoT applications. In such applications, the sensing operation is often performed at a relatively low frequency, and sometimes it is heavily duty-cycled, or it should be triggered by particular events or thresholds. The paper reviews why dynamic sensor interface architectures are a good choice in this context, and gives several design examples that can operate dynamically and that can be triggered by a single clock pulse. Suitable ADC design strategies are explained, and two exemplary sensor interfaces are described: a capacitive sensor interface, and a resistor-based temperature sensor interface including analog correction techniques. Both designs are reviewed and the main features in terms of efficiency and performance are discussed.

Nowadays, many battery-operated SoCs for loT and environmental monitoring applications are equipped with temperature sensors. In these miniaturized systems, power and area are two critical concerns. One challenge for temperature sensors is that they are sensitive to process corners and random mismatch. Generally, a 2-point trim and systematic non-linear error removal are required, especially for resistor-based sensing front-ends with two types of resistors, whose spread is partially uncorrelated [1], [2]. These corrections are done off-chip and digitally in most publications. In particular for low power sensors, they may consume more power and area than the sensor itself when integrated on-chip [3]. This work presents a resistive temperature sensor that integrates on-chip analog offset, gain and non-linearity correction techniques, while keeping state-of-the-art power and size performance. The prototype consumes 2.98pJ/conversion with an area of 0. 0023textmm 2 including all the correction techniques and achieves +0.7/-0.6 circC inaccuracy.