Abstract
This paper proposes a reconfigurable sensor analog front-end using low-noise chopper-stabilized delta-sigma capacitance-to-digital converter (CDC) for capacitive microsensors. The proposed reconfigurable sensor analog front-end can drive both capacitive microsensors and voltage signals by direct conversion without a front-end amplifier. The reconfigurable scheme of the front-end can be implemented in various multi-mode applications, where it is equipped with a fully integrated temperature sensor. A chopper stabilization technique is implemented here to achieve a low-noise characteristic by reducing unexpected low-frequency noises such as offsets and flicker noise. The prototype chip of the proposed sensor analog front-end is fabricated by a standard 0.18-μm 1-poly-6-metal (1P6M) complementary metal-oxide-semiconductor (CMOS) process. It occupies a total active area of 5.37 mm2 and achieves an effective resolution of 16.3-bit. The total power consumption is 0.843 mW with a 1.8 V power supply.
Highlights
The emergence of the Internet of Things (IoT) in recent years has greatly influenced the field of electronics, and the demand for the development of IoT based applications has increased
With the wide use of capacitive microsensors, many research works on capacitive microsensor interface circuit techniques have been reported [10–22]
The successive approximation register (SAR) capacitance-to-digital converter (CDC) scheme can achieve low power consumption and small size; it severely suffers from the effect of parasitic capacitance due to the direct connection of the capacitive sensor to the input of the comparator without the pre-amplifier
Summary
The emergence of the Internet of Things (IoT) in recent years has greatly influenced the field of electronics, and the demand for the development of IoT based applications has increased. A capacitive sensor readout circuit with charge sensing amplifier (CSA) for pre-amplification of the sensor signal and a delta-sigma modulator can achieve high resolution because of its low-noise characteristic [17], the chip size and power consumption increase due to the additional CSA. The main strength of the proposed sensor analog front-end is the reconfigurable scheme, which can drive capacitive sensors and voltage signals without a front-end amplifier by direct conversion in the second-order incremental delta-sigma converter scheme. It employs a chopper stabilization technique to achieve a low-noise characteristic.
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