A Capacitance-Ratio-Modulated Current Front-End Circuit With Pulsewidth Modulation Output for a Capacitive Sensor Interface

Sheu, Meng-Lieh; Hsu, Wen Lin; Tsao, Lin-Jie

doi:10.1109/tim.2011.2161929

Cited by 37 publications

(24 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, PWM-based solutions are synchronous circuit needing a clock line to synchronize the interfacing operation, while their measurement time and resolution are typically independent from the sensor capacitance. These kinds of interface solutions, typically showing straightforward architectures with a high tolerance to common-mode noise/disturbs and to parasitic components as well as to supply voltage drifts, allows for covering wide capacitive variation ranges and can also be combined with a digital system to easily measure the time intervals (e.g., through counters) [25][26][27][28][29][30][31][32][33][34]. Recently, also mixed-signal and digital sensor systems are becoming prevalent, so that new topologies of sensor conditioning circuits have been also introduced.…”

Section: Introductionmentioning

confidence: 99%

A Capacitance-to-Time Converter-Based Electronic Interface for Differential Capacitive Sensors

2019

View full text Add to dashboard Cite

In this paper we present an oscillating conditioning circuit, operating a capacitance-to-time conversion, which is suitable for the readout of differential capacitive sensors. The simple architecture, based on a multiple-feedbacks structure that avoids ground noise disturbs and system calibrations, employs only three Operational Amplifiers (OAs) and a mixer implementing a square wave oscillator that provides an AC sensor excitation voltage. It performs a Period Modulation (PM) and a Pulse Width Modulation (PWM) of the output signal proportionally to the sensor differential capacitance values. The sensor variation range and the detection sensitivity can be easily set through the additional resistors. Preliminary PSpice simulation results have shown a good agreement with theoretical calculations as well as a linear response with a high detection sensitivity of differential capacitive sensors having a baseline in the range [2.2 ÷ 180 pF]. Moreover, different experimental measurements have been also performed by implementing the circuit on a laboratory breadboard using commercial discrete components so validating the idea and providing the circuit performances with different kind of differential capacitive sensors achieving detection resolutions of about 0.1 fF in an overall differential capacitive variation range that is equal to ±15.8 pF. The achieved results demonstrate that the proposed interface solution is suitable for on-chip integration with different kinds of differential capacitive sensing devices, such as Micro-Electro-Mechanical-System (MEMS), force/position, and humidity sensors in biomedical and robotics applications.

show abstract

Section: Introductionmentioning

confidence: 99%

A Capacitance-to-Time Converter-Based Electronic Interface for Differential Capacitive Sensors

2019

View full text Add to dashboard Cite

show abstract

“…The modulation-based circuits are based on sigma-delta converter [11]- [14], successive approximation register (SAR) analog-to-digital converter (ADC) [14], [15], chopper modulation [16]- [18], pulsewidth modulation (PWM) [19]- [21], and frequency modulation (FM) configurations [24]- [30]. The converters require much faster analog circuits as the sampling rate is much higher than the effective bandwidth as well as a digital decimation filter that is a challenge to design.…”

Section: Introductionmentioning

confidence: 99%

“…The PWM based interface circuits exploit semi-digital approach where the capacitance changes are encoded in time-domain to modulate the period or pulse width of a digital signal [19]- [22]. This technique requires a fast digital counter to convert the time or pulse-width variation into a digital output [23].…”

Section: Introductionmentioning

confidence: 99%

A MEMS Interface IC With Low-Power and Wide-Range Frequency-to-Voltage Converter for Biomedical Applications

Redouté

Yuce

2016

IEEE Trans. Biomed. Circuits Syst.

View full text Add to dashboard Cite

This paper presents an interface circuit for capacitive and inductive MEMS biosensors using an oscillator and a charge pump based frequency-to-voltage converter. Frequency modulation using a differential crossed coupled oscillator is adopted to sense capacitive and inductive changes. The frequency-to-voltage converter is designed with a negative feedback system and external controlling parameters to adjust the sensitivity, dynamic range, and nominal point for the measurement. The sensitivity of the frequency-to-voltage converter is from 13.28 to 35.96 mV/MHz depending on external voltage and charging current. The sensitivity ranges of the capacitive and inductive interface circuit are 17.08 to 54.4 mV/pF and 32.11 to 82.88 mV/mH, respectively. A capacitive MEMS based pH sensor is also connected with the interface circuit to measure the high acidic gastric acid throughout the digestive tract. The sensitivity for pH from 1 to 3 is 191.4 mV/pH with 550 μV(pp) noise. The readout circuit is designed and fabricated using the UMC 0.18 μm CMOS technology. It occupies an area of 0.18 mm (2) and consumes 11.8 mW.

show abstract

“…In this way, quasi-digital temperature sensors, that is, those with time-, frequency-, or duty-cycle-codified information [7], are a suitable solution due to the combination of the inherent simplicity in analog devices with the accuracy and noise immunity typical of digital sensors; taking advantage of the μC time measurement capability [8], concretely, frequency-output sensors arise as the optimal choice [9]: the temperature information is codified into frequency and lead to the μC using a single port; then, the final digitalization is made using the μC internal clocks, with a resolution that mainly depends on the frequency-to-code conversion method.…”

Section: Introductionmentioning

confidence: 99%

1.2 V–0.18-$\mu \text{m}$ CMOS Temperature Sensors With Quasi-Digital Output for Portable Systems

Azcona

Calvo

Medrano

et al. 2015

IEEE Trans. Instrum. Meas.

View full text Add to dashboard Cite

This paper presents two compact frequency-output temperature sensors based on a multivibrator current-tofrequency converter to improve sensor linearity over a wide temperature range featuring low-voltage low-power operation. Both sensors have been fabricated in a low-cost 0.18-µm CMOS technology with a single 1.2 V supply voltage. They show high linearity over a temperature range of −40°C to +120°C, achieving an inaccuracy of ±1°C, with sensitivities of 335 Hz/°C and 460 Hz/°C, a power consumption below 3 µW, and an area below 0.025 mm 2 . These features make them a highly suitable solution in the case of portable applications.Index Terms-CMOS integrated circuits, low-voltage lowpower, quasi-digital output, smart sensors, temperature to frequency, wireless sensor network (WSN).

show abstract

A Capacitance-Ratio-Modulated Current Front-End Circuit With Pulsewidth Modulation Output for a Capacitive Sensor Interface

Cited by 37 publications

References 15 publications

A Capacitance-to-Time Converter-Based Electronic Interface for Differential Capacitive Sensors

A Capacitance-to-Time Converter-Based Electronic Interface for Differential Capacitive Sensors

A MEMS Interface IC With Low-Power and Wide-Range Frequency-to-Voltage Converter for Biomedical Applications

1.2 V–0.18-$\mu \text{m}$ CMOS Temperature Sensors With Quasi-Digital Output for Portable Systems

Contact Info

Product

Resources

About