High‐resolution continuous‐time interface for micromachined capacitive accelerometer

2011 Asia Pacific Conference on Postgraduate Research in Microelectronics &Amp; Electronics

et al. 2011

This paper presents a closed-loop interface circuit for high quality factor (Q) capacitive micro-accelerometers. High-Q sensing element is desirable for high resolution, but makes the loop control a great challenge. Considering this, closed-loop implementation utilizing analog force feedback is preferred rather than electromechanical A~, which is very popular in recent years. To overcome the non-linearity problem of traditional analogue force feedback scheme, pulse width modulation (PWM) force feedback is developed. The chip measures 2.5x2.5mm 2 in a commercial 0.35J.1m CMOS process. Using a high-Q capacitive micro-accelerometer, the interface circuit attains an input range of ±1.25g, a white noise equivalent acceleration (NEA) of 17J.1g/~Hz, a less than 0.1% non-linearity from a single 5V supply, and a good degree of robustness.

Section: Pwm Force Feedbackmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electromechanical closed-loop with high-Q capacitive micro-accelerometers and pulse width modulation force feedback

Yang

2011 Asia Pacific Conference on Postgraduate Research in Microelectronics &Amp; Electronics

et al. 2011

“…[10][11][12][13] If there is any contradiction regarding the optimisation of the visible parameters, the design should reach a compromise.…”

Section: The Basic Principle Of the Closed-loop Accelerometermentioning

confidence: 99%

Study of self-calibrating MEMS accelerometers

Chen

et al. 2015

AIP Advances

Micro-electromechanical System(MEMS) accelerometers are widely used in a number of inertial navigation systems and vibration detection system thanks to their small size, low cost and low power consumption. In order to improve their performance, the accelerometers have been designed to compensate the zero-bias caused by process variations. A new method of self-calibration sensitivity applies a self-test structure to simulate standard acceleration; depending on the standard and real-time values of the accelerometer’s output and by adjustment of the time division feedback, the scale factor of capacitive accelerometers can be flexibly adjusted to achieve sensitivity in self-calibrating MEMS accelerometers. Moreover, this research also uses the following: a PID feedback structure to improve the stability of the closed-loop system; a correlated double sampling (CDS) circuit to attenuate noise, which can eliminate zero drift caused by offset voltage of the pre-amplifier; a time division multiplexing electrostatic force feedback circuit to achieve the operation of a closed-loop micro-accelerometer. The structure can completely avoid electrostatic feedback coupling with a capacitance change detection circuit, which can also improve the bandwidth and stability of the accelerometer. By means of capacitance compensation array the zero-bias performance of accelerometers can be improved. The bias stability of the accelerometer can be reduced from 173mg to 31mg by testing.

“…However, the measured closed-loop system did not achieve sub-g equivalent resolution. In [4] and [12], a sub-g equivalent resolution continuous-time capacitive accelerometer interface using a high-Q mechanical element was reported. In this method, high-resolution digital output was obtained by digitizing the feedback signal using a high-resolution ADC.…”

Section: Introductionmentioning

confidence: 99%

A Closed-Loop <formula formulatype="inline"> <tex Notation="TeX">$\Sigma\Delta$</tex></formula> Interface for a High-Q Micromechanical Capacitive Accelerometer With 200 ng/<formula formulatype="inline"><tex Notation="TeX">$ \surd$</tex></formula>Hz Input Noise Density

IEEE J. Solid-State Circuits

Yin

2015

In this paper, a fully-differential high-order switchedcapacitor (SC) sigma-delta interface in a standard 0.5 m CMOS technology for a micromechanical capacitive accelerometer is presented. A 1 bit digital output is attained by the interface circuit based on a low-noise front-end and a back-end third-order SC modulator, avoiding the use of a separate high-resolution converter to digitize the analog feedback signal. In addition, a micromechanical capacitive sensor element with a high quality factor (high-Q) is used to achieve high-resolution. Furthermore, closed-loop operation and electrical compensation are employed for damping the high-Q to ensure the stability of the high-order system. The sensor consumes 23 mW of power from a single 7 V supply at a sampling clock of 250 kHz. Meanwhile, a sensitivity of 1.896 V/g is achieved with a noise floor of lower than 200 ng Hz in low-frequency. The sensor has a nonlinearity of 0.15% with an input range of 1.2g. The bandwidth (BW) is 300 Hz and the bias instability is 18 g.Index Terms-High quality factor, high-order, interface circuit, micromechanical capacitive accelerometer, sigma-delta modulator. 0018-9200