27.7 A 0.05mm&lt;sup&gt;2&lt;/sup&gt; 1V capacitance-to-digital converter based on period modulation

He, Yuming; Chang, Zu-yao; Pakula, L.; Shalmany, Saleh Heidary; Pertijs, Michiel A. P.

doi:10.1109/isscc.2015.7063138

Cited by 28 publications

(23 citation statements)

References 2 publications

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“…Depending on how the capacitive sensor is connected to the electronic interface circuit, the interface principles can be categorized as (1) capacitive sensors with a grounded target electrode [9][10][11][12][13] ; (2) capacitive sensors with an active target electrode [14][15][16][17][18][19][20][21][22] ; and (3) capacitive sensors with a floating target electrode. 23,24 It should be mentioned that in all categories, to reduce external interference, the sensor plates need to be connected to the interface via a shielded cable.…”

Section: Discussionmentioning

confidence: 99%

“…A performance summary and a comparison with state-of-the-art interfaces [14][15][16][17][18][19][20][21] are shown in Table 1. The energy efficiency of different interfaces is evaluated by using the two well-known energy efficiency figure-of-merits (FOM) as follows [13][14][15][16][17][18][19][20] :…”

Section: Comparison and Discussionmentioning

confidence: 99%

“…where P D is the power consumption of the interface, T M is the conversion time, and CR and ENOB are the capacitance resolution and effective resolution in bits, which are calculated as [13][14][15][16][17][18][19][20] ENOB ¼…”

Section: Comparison and Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Design trade‐offs of a capacitance‐to‐voltage converter with a zoom‐in technique for grounded capacitive sensors

Bijargah

Heidary

Torkzadeh

et al. 2018

Circuit Theory & Apps

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This paper presents a low-power, high-precision capacitance-to-voltage converter (CVC) for grounded capacitive sensors. To measure very small capacitance variations in the presence of a large offset capacitance, a new zoom-in structure is proposed. The major non-idealities of the CVC such as the settling error, charge injection, and parasitic capacitance of the switches are minimized through an optimized design. Accordingly, it is shown that the zoom-in technique can significantly reduce many of these errors. The effect of the parasitic capacitances around the sensor capacitance is significantly reduced by using a switched-capacitor-based active-shielding technique. The interface is designed as an integrated circuit using a standard 0.18-μm CMOS technology. Simulation results show that for a sensor capacitor with a nominal value of 10 pF, variation of only 200 fF, and parasitic capacitance of up to 20 pF, a worst-case capacitance error of 0.2 fF can be achieved by taking into account the layout mismatches and the interconnection effects. The achieved latency is 100 μs, and the CVC consumes only 80 μA from a 2-V power supply. The simulated input capacitance resolution for this latency is 123 aF, which is quite close to our calculated resolution (126 aF). This resolution corresponds to an energy efficiency of 9.82 pJ/Step. A temperature sweep simulation has been performed over the temperature range from −45°C to 125°C to demonstrate the small thermal drift of the designed circuit.

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Section: Discussionmentioning

confidence: 99%

Section: Comparison and Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Design trade‐offs of a capacitance‐to‐voltage converter with a zoom‐in technique for grounded capacitive sensors

Bijargah

Heidary

Torkzadeh

et al. 2018

Circuit Theory & Apps

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“…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

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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.

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“…Recently, several solutions for capacitive sensor interfaces with digital output have been reported. These reported solutions include the use of a CVC followed by an analog‐to‐digital converter (ADC), period modulation (PM),, sigma‐delta modulation, and pulse‐width modulation (PWM) . In PM CPCs, the resolution can be traded for conversion time by counting the duration of multiple periods using a digital divider, which makes them quite flexible …”

Section: Introductionmentioning

confidence: 99%

An accurate and power‐efficient period‐modulator‐based interface for grounded capacitive sensors

Bijargah

Heidary

Torkzadeh

et al. 2019

Circuit Theory & Apps

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A low-power and high-resolution capacitance-to-period converter (CPC) based on period modulation (PM) for subnanometer displacement measurement systems is proposed. The presented circuit employs the interface developed in a previous work, "a grounded capacitance-to-voltage converter (CVC) based on a zoom-in structure," further improving its performance through a symmetrical design of the applied autocalibration technique. The scheme is based on the use of a relaxation oscillator. To minimize the error contributed by the CPC circuitry, different precision techniques such as chopping, autocalibration, and active shielding are applied. The proposed CPC is realized in a 0.18-μm complementary metal-oxide-semiconductor (CMOS) technology, occupies an area of 0.5 mm 2 , and consumes 135 μA from a 2-V power supply. In order to achieve optimal performance and avoid overdesigning, a noise estimation of various parts of the CPC has been done. Accordingly, for a 10-pF sensor capacitance, the overall CPC demonstrates a capacitance resolution of 0.5 fF for a latency of 128 microseconds, corresponding to an effective number of bits (ENOB) of 12.5 bits and an energy efficiency of 6 pJ/step. The nonlinearity error has been evaluated as well, resulting in a less than 0.03% full-scale span (FSS).

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27.7 A 0.05mm<sup>2</sup> 1V capacitance-to-digital converter based on period modulation

Cited by 28 publications

References 2 publications

Design trade‐offs of a capacitance‐to‐voltage converter with a zoom‐in technique for grounded capacitive sensors

Design trade‐offs of a capacitance‐to‐voltage converter with a zoom‐in technique for grounded capacitive sensors

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

An accurate and power‐efficient period‐modulator‐based interface for grounded capacitive sensors

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