Abstract
This paper presents a low-noise reconfigurable sensor readout circuit with a multimodal sensing chain for voltage/current/resistive/capacitive microsensors such that it can interface with a voltage, current, resistive, or capacitive microsensor, and can be reconfigured for a specific sensor application. The multimodal sensor readout circuit consists of a reconfigurable amplifier, programmable gain amplifier (PGA), low-pass filter (LPF), and analog-to-digital converter (ADC). A chopper stabilization technique was implemented in a multi-path operational amplifier to mitigate 1/f noise and offsets. The 1/f noise and offsets were up-converted by a chopper circuit and caused an output ripple. An AC-coupled ripple rejection loop (RRL) was implemented to reduce the output ripple caused by the chopper. When the amplifier was operated in the discrete-time mode, for example, the capacitive-sensing mode, a correlated double sampling (CDS) scheme reduced the low-frequency noise. The readout circuit was designed to use the 0.18-µm complementary metal-oxide-semiconductor (CMOS) process with an active area of 9.61 mm2. The total power consumption was 2.552 mW with a 1.8-V supply voltage. The measured input referred noise in the voltage-sensing mode was 5.25 µVrms from 1 Hz to 200 Hz.
Highlights
The market for microsensors based on micro-electromechanical systems (MEMS) technology has grown rapidly in recent years, with many attempts using the Internet of Things (IoT) to integrate various microsensors into systems for safety, health, convenience, and industry [1].Microsensors provide output signals based on changes in voltage, current, resistance, or capacitance by utilizing specific physical/chemical variations
Depending on the voltage/resistive, current, or capacitive-sensing modes, the chopper-stabilized, multi-path operational amplifiers, A1M and A2M can be reconfigured to three amplifier types: a voltage buffer, trans-impedance amplifier (TIA), and a correlated double sampling (CDS) scheme
Depending on the voltage/resistive, C1 chopper-stabilized, multi-path operational amplifiers, A1M and A2M can be reconfigured to three amplifier types: a voltage buffer, A 2Mtrans-impedance amplifier (TIA), and a CDS scheme
Summary
The market for microsensors based on micro-electromechanical systems (MEMS) technology has grown rapidly in recent years, with many attempts using the Internet of Things (IoT) to integrate various microsensors into systems for safety, health, convenience, and industry [1]. The cost can be drastically increased as the required modality of sensors increases To solve this problem, several research papers have presented a multimodal sensing system that shares a single reconfigurable readout circuit [9,10,11,12,13]. The low-frequency noise can be amplified by the IA and can limit the output dynamic range To solve this problem, dynamic offset cancellation techniques, including chopper stabilization or correlated double sampling (CDS), are widely used [14,15,16]. This paper presents a low-noise multimodal reconfigurable sensor readout circuit for voltage/current/resistive/capacitive microsensors. We proposed a reconfigurable structure that can accommodate voltage/current/resistance/capacitive sensors Both low-noise and wide-bandwidth characteristics were achieved by adopting multiple dynamic offset cancellation (DOC) techniques. In the discrete-time mode, to eliminate the residual offset and low-frequency noise components, the correlated double sampling technique was applied
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