A digital readout technique for capacitive sensor applications

Kung, Jaeha; Lee, H.-S.; Howe, Roger T.

doi:10.1109/4.348

Cited by 55 publications

(11 citation statements)

References 11 publications

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“…This effect is called charge injection and leads to errors in the output voltage of the integrator. This problem was already identified in the first switched-capacitor circuits [27] and has been analyzed in detail in later publications [18,[28][29][30].…”

Section: Charge Injection Compensationmentioning

confidence: 98%

“…Relaxation oscillators using the sensing capacitor as frequencydetermining element have also been developed [17]. The most popular approach to read-out capacitive sensors with high resolution and good suppression of parasitics is switched capacitor design [18][19][20][21][22]. Table 1.2.2 compares the performances of the different designs.…”

Section: Read-out Circuitrymentioning

confidence: 99%

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CMOS Single‐chip Gas Detection Systems: Part II

2003

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Sensor arrays based on industrial CMOS-technology combined with post-CMOS micromachining (CMOS MEMS) are a promising approach to low-cost sensors. In the first part of this article [1], the state of research on CMOS-based gas sensor systems was reviewed, and a platform technology for monolithic integration of three different transducers on a single chip was described. In this second part, the transduction principles of three polymer-based gas sensors are detailed and the read-out circuitry is portrayed. The first transducer is a micromachined resonant cantilever. The absorption of analyte in the chemically sensitive polymer causes shifts in resonance frequency as a consequence of changes in the oscillating mass. The cantilever acts as the frequency-determining element in an oscillator circuit, and the resulting frequency change is read out by an on-chip counter. The second transducer is a planar capacitor with polymer-coated interdigitated electrodes. This transducer monitors changes in the dielectric constant upon absorption of the analyte into the polymer matrix. The sensor response is read out as a differential signal between the coated sensing capacitor and a passivated reference capacitor, both of which are incorporated into the input stage of a switched capacitor second-order RD-modulator. The third transducer is a thermoelectric calorimeter, which detects enthalpy changes upon ab-/desorption of analyte molecules into a polymer film located on a thermally insulated membrane. The enthalpy changes in the polymer film cause transient temperature variations, which are detected via polysilicon/aluminum thermocouples (Seebeck effect). The small signals in the lVrange are first amplified with a low-noise chopper amplifier, then converted to a digital signal using a RD-A/D-converter and finally decimated and filtered with a digital decimation filter.

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Section: Charge Injection Compensationmentioning

confidence: 98%

Section: Read-out Circuitrymentioning

confidence: 99%

CMOS Single‐chip Gas Detection Systems: Part II

2003

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“…Several circuits based on switchedcapacitor techniques are available in the literature for realization of such converters [1,2,3,4,5]. In these circuits, the capacitance deviation between a capacitive sensor (or active sensor) and a reference capacitor (or dummy sensor) is detected via charge subtraction operation, and then subjected to various analogue-to-digital (A/D) conversion operations: cyclic (also known as algorithmic) [1], charge-balancing [2], charge-redistribution [3], dual-slope [4], sigma-delta [5]. Although these circuits are amenable to integration in a monolithic chip using a CMOS process, problems appear that are inherent to all switched-capacitor circuits: nonideal effects due to the charge injection of MOSFET switches.…”

Section: Introductionmentioning

confidence: 99%

Capacitance deviation-to-time interval converter using current-tunable Schmitt triggers

Kim

Park²,

Chung

et al. 2011

IEICE Electron. Express

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Abstract:A capacitance deviation-to-time interval converter is presented for interfacing capacitive sensors. It consists of two ramp integrators, two current-tunable Schmitt triggers, and two logic gates. A prototype circuit built using discrete components exhibits a resolution as high as 13 bits and a linearity error less than ±0.2% when the output pulse width is counted by a 20 MHz clock signal. Its application to a humidity sensor is also presented.

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“…Proper design of switched-capacitor circuits, on the other hand, can eliminate these effects. This property, along with their high sensitivity, has made them very attractive for capacitive sensor readout [26]- [28]. A switchedcapacitor front-end consisting of a low-noise charge integrator and a digitally programmable gain stage was developed for capacitance readout.…”

Section: ) Programmable Capacitive Readoutmentioning

confidence: 99%

Highly Adaptive Transducer Interface Circuit for Multiparameter Microsystems

Zhang

Zhou

Mason

2007

IEEE Trans. Circuits Syst. I

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Abstract-A reconfigurable transducer interface circuit that combines the communication and signal conditioning necessary to link a variety of sensors and actuators to a microsystem controller is reported. The adaptive readout circuitry supports high-resolution signal acquisition from capacitive, resistive, voltage and current mode sensors with programmable control of gain and offset to match sensor range and sensitivity. The chip accommodates sensor self test and self calibration and supports several power management schemes. It provides digital and analog outputs to control actuators and a standard interface to peripheral components. The 2.2 2.2 mm CMOS chip was fabricated in 0.5-m, 3-metal, 2-poly process, dissipates 50 W at 3.3 V in a typical multisensor application utilizing periodic sleep mode, and can read out a wide range of sensors with high sensitivity. A prototype microsystem with a microcontroller and MEMS pressure, humidity, and temperature sensors has been implemented to characterize interface chip performance.

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A digital readout technique for capacitive sensor applications

Cited by 55 publications

References 11 publications

CMOS Single‐chip Gas Detection Systems: Part II

CMOS Single‐chip Gas Detection Systems: Part II

Capacitance deviation-to-time interval converter using current-tunable Schmitt triggers

Highly Adaptive Transducer Interface Circuit for Multiparameter Microsystems

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