Abstract
This paper presents the design and implementation of an auto-tuning continuous-time bandpass sigma-delta (ΣΔ) modulator for micro-electromechchanical systems (MEMS) gyroscope readout systems. Its notch frequency can well match the input signal frequency by adding a signal observation to the traditional ΣΔ modulator. The filter of the observation adopts the same architecture as that of the traditional ΣΔ modulator, allowing the two filters to have the same response to input signal change, which is converted into a control voltage on metal-oxide semiconductor (MOS) resistance in the filters. The automatic tuning not only works to solve the mismatch problem caused by process error and temperature variation, but can also be applied to the interface circuit of gyroscopes with different resonant frequencies. The circuit is implemented in a 0.18-μm complementary metal-oxide semiconductor (CMOS) process with a core area of 2.4 mm2. The improved modulator achieves a dynamic range of 106 dB, a noise floor below 120 dB and a maximum signal-to-noise and distortion ratio (SNDR) of 86.4 dB. The tuning capability of the chip is relatively stable under input signals from 6 to 15 kHz at temperatures ranging from −45 to 60 °C.
Highlights
Micro-electromechanical systems (MEMS) gyroscopes are widely used to measure the rotation rate and have many advantages, such as low cost, small size, low power consumption, good complementary metal-oxide semiconductor (CMOS) compatibility, and suitability for batch fabrication [1]
Among the various techniques for implementing the inertial sensor digital output, sigma-delta (Σ∆) modulators are widely used, since they combine the benefits of feedback and inherent analog-to-digital converter (ADC) [4], which can increase the stability of the system
A chip micrograph of the ASIC is shown in Figure 12, which was fabricated in SMIC 0.18-μm power supply12, voltage gyroscope achieve high
Summary
Micro-electromechanical systems (MEMS) gyroscopes are widely used to measure the rotation rate and have many advantages, such as low cost, small size, low power consumption, good complementary metal-oxide semiconductor (CMOS) compatibility, and suitability for batch fabrication [1]. It is necessary to tune the Σ∆ ADC center frequency in the whole the wholeprocess operation process withcalibration an online calibration module is able to work continuously [11]. A calibration module added to the bandpass modulator can track the frequency change of the input signal. Modulator to solve the filter tuning problem, which can increase frequency range and tuning accuracy. The control voltage Vctl which is generated by the signal observation can tune the time observation. The control voltage V which is generated by the signal observation can tune the time constants of the electronic filters to further change the center frequency of the bandpass Σ∆ modulator. Constants of the electronic filters to further change the center frequency of the bandpass ΣΔ modulator
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