Tingting Tao

A control and readout circuit with capacitive mismatch auto-compensation for MEMS vibratory gyroscope

In this paper, a control and readout circuit for MEMS vibratory gyroscope is described, including closed- loop driving axis and open-loop sensing axis. Capacitive mismatch auto-compensation has been implemented in this system to suppress the influence to the output due to the mismatch of gyroscope capacitors. The ASIC is fabricated in a 0.35um CMOS process. The test of the ASIC is performed with a MEMS vibratory gyroscope. The test result shows that the non-linearity is less than 0.1% within angular velocity range of -300°/s to 300°/s.

A high-voltage interface circuit for MEMS vibratory gyroscope

In this paper, a high-voltage interface circuit has been designed and implemented for MEMS gyroscope. Continuous-time charge sensitive amplifier with chopping stabilization technique is used in the conversion stage to achieve low noise performance. A closed driving loop for MEMS gyroscope which applying multiple supply voltages is presented. The chip is fabricated in a 0.35um 5V/12V high-voltage process. The test of the chip is performed with a MEMS vibratory gyroscope. The result shows that the driving output of the ASIC can ensure a stable oscillation in the driving axis.

A LOW-NOISE HIGH-VOLTAGE INTERFACE CIRCUIT FOR CAPACITIVE MEMS GYROSCOPE

This paper presents a high-voltage control and readout interface circuit implemented for capacitive Micro-Electro-Mechanic System (MEMS) gyroscope. A charge sensitive amplifier (CSA) with chopper technique is used to accomplish low-noise capacitive sensing. The stabilization of the closed drive loop is maintained by an auto gain controller (AGC) and an adjustable phase shifter. The outputs of the ASIC directly drive the gyroscope after buffered by an on-chip high-voltage level shifter. The chip is fabricated in a 0.35 um 5 V/12 V Bipolar, CMOS and DMOS (BCD) process. The test of the chip is performed with a MEMS vibratory gyroscope. The result shows that the Application Specific Integrated Circuit (ASIC) can ensure a stable oscillation in the drive axis, and the noise floor is 0.0015°/s/√Hz within 100 Hz.

A CAPACITIVE INTERFACE CIRCUIT WITH CAPACITOR MISMATCH AUTO-COMPENSATION FOR MEMS GYROSCOPE

In this paper, a capacitive interface circuit with capacitor mismatch auto-compensation has been designed and implemented for MEMS gyroscope. An on-chip capacitor array controlled by an 8-bit SAR logic circuit is selected to be connected in parallel with the minor one of the two differential gyroscope capacitors, making the two capacitors equal. The compensation progress takes eight periods of the clock at power-on and then will be turned off automatically. The chip is fabricated in a 0.35 μm CMOS process. The test of the chip is performed with a vibratory gyroscope on the condition of a closed-loop control in the drive mode, and the measurement shows that the minimum capacitive compensation is 3.5 fF. Within -300°/s to 300°/s of rotation rate input range, the nonlinearity is less than 0.1%.

A low-noise SC-type interface asic for a closed-loop MEMS gyroscope

This paper presents a low-noise SC-type interface ASIC for a closed-loop MEMS vibratory gyroscope. An AC sensing method is employed to convert the amplitude-modulated capacitive signal to voltage signal. The interface CSA (charge sensitive amplifier) is followed by a CDS (correlated double sampling) circuit to reduce low frequency noise and eliminate offset. The system realizes a closed-loop control in the driving and sensing mode. The ASIC is fabricated in 0.18um CMOS process and occupies 2.9×1.7 mm2.

Designing of a micromachined gyroscope system with a closed-loop DC biased interface ASIC

In this paper, a micromachined gyroscope system composed of a vibratory gyroscope with its interface ASIC is presented. The system adopts a DC sensing method to detect the capacitive motion, which is insensitive to the mismatch of the gyroscope capacitors and can eliminate high frequency signals from the chip. Therefore it offers a commendable noise performance with simplified topology. Low noise design can be achieved by a continuous-time charge sensitive amplifier with the input-referred noise voltage of 9.833 nV/rtHz at 10 kHz. A novel high voltage (HV) buffer is adopted in the drive mode to strengthen its drive signal, so that the common-mode voltage of it is made at 5 V that is compatible with the gyroscope. The HV buffer utilizes two sets of power supply to achieve both good noise performance and HV output. The ASIC chip is fabricated in the 0.35 μm 2P4M BCD HV process, and is 2.5×2.0 mm2 in dimension. The test results prove that the system achieves a stable closed-loop oscillation in the drive mode. Furthermore, the in-phase demodulation result of the gyroscope system achieves a nonlinearity of 0.14% within the sense range of 0°–500°/s.

A closed-loop system with DC sensing method for vibratory gyroscopes

The paper presents a closed-loop system scheme with DC sensing method for vibratory gyroscopes. A DC sensing method is employed to convert the amplitude-modulated capacitive signal to voltage. The system realizes a closed-loop control in the driving mode. A high voltage (HV) drive signal which is compatible with the gyro is obtained by the on-chip level shifter. The ASIC occupies 2.5×2.0mm2 in a 0.35μm BCD process. The system requires a differential supply of ±12V and can work under a resonant frequency from 3 to 10 kHz.

A low-noise HV interface circuit for MEMS vibratory gyroscope

The paper presents a low-noise high voltage (HV) CMOS Interface ASIC designed for MEMS vibratory gyroscopes. A closed-loop control is realized in the driving mode. An in-chip level shifter is designed in the loop to achieve a high DC voltage level of 5V which can excite the gyroscope. A DC biasing method is adopted in the interface circuit to convert the amplitude-modulated capacitive signal into voltage. The chip occupies 2.5 × 2.0mm2 in a 0.35 µm 2P3M BCD HV process, which offers buried layer and high voltage N-well isolation to block out the potential coupling noise. Simulation results show that the drive axis can accomplish a closed-loop self-oscillation of the MEMS gyroscope.

Capacitor mismatch auto-compensation for MEMS gyroscope differential capacitive sensing circuit

A capacitor mismatch auto-compensation circuit has been designed and implemented for MEMS gyroscope differential capacitive sensing circuit. An in-chip capacitor array that controlled by the 7-bit SAR is selected to be connected in parallel with one of the gyroscope capacitor, making the two differential capacitors of the gyroscope equal. The compensation progress only takes eight periods of the clock at the start and will be turned off afterward automatically. The chip is fabricated in a 0.35um CMOS process. The test of the chip is performed with a vibratory gyroscope on the condition of a closed-loop control in the drive mode, and the measurement shows that the minimum capacitive compensation is 3.5fF.

A novel PLL-based phase control technique in the digitalized closed-loop gyroscope interface circuit

This paper presents a novel phase control technique based on the charge-pump PLL in an analog-digital-combined closed-loop interface circuit. The phase control resolution is 0.004° with the control range of 85~95° under worst case. The interface circuit achieves the resolution of 2.38aF with a maximum equivalent sensitivity of 98.9mV/aF in simulation. The chip is being fabricated in a 0.18um CMOS process and is 3×1.8mm2 in size.