Papers by Author: Peng Fei Wang

Abstract: This paper presents a fourth-order sigma delta (ΣΔ)modulator applied in micro-inertial sensors. After a introduction of sigma-delta modulator and its application in micro-inertial sensors, the system-level analysis and design is given and the gain coefficients is calculated. By the use of root locus, the stability of high order ΣΔ modulator is analyzed and it is got the minimum value of quantizer gain k is 0.287. The simulation shows that the signal to noise ratio (SNR) is 121.6 dB and the effective number of bits (ENOB) is 19.91 bits. When input level is smaller than -6 dBFs, the quantizer and integrators would not be overload and work well.

Abstract: In this paper a high-performance closed-loop fourth-order sigma-delta (ΣΔ) micro-accelerometer is presented. After a introduction of sigma-delta accelerometer, system-level analysis and design of a fourth-order sigma-delta micro-accelerometer is given. The simulation result shows that an accelerometer with 107dB signal to noise ratio (SNR) and 17.5 bits effective number of bits (ENOB) is achieved. Through the root locus analysis, it is got that accelerometer is stable when quantization gain is bigger than 0.262. The accelerometer gets a good linearity and it becomes overload when input signal level is greater than -5dBFS.

Abstract: The reference is an important part in the accelerometer system. With the development of science and technology, the request of the performance of accelerometers is increasingly higher and the precision of reference directly affects the performance of accelerometers. Therefore, a reference voltage applicable to accelerometers is presented based on the analysis of basic principles of conventional bandgap reference (BGR) in this paper. A high-order curvature compensation technique, which uses a temperature dependent resistor ratio generated by a high poly resistor and a nwell resistor, effectively serves to reduce temperature coefficient of proposed reference voltage circuit and to a large extent improve its performance. To achieve a high power supply rejection ratio (PSRR) over a broad frequency range, a pre-regulator is introduced to remain the supply voltage of the core circuit of BGR relatively independent of the global supply voltage. The proposed circuitry is designed in standard 2.0μm CMOS process. The simulated result shows that the average temperature coefficient is less than 2ppm/°C in the temperature range from -40 to 120°C. The improvement on temperature coefficient (TC) is about 10 times reduction compared to the conventional approach. And the PSR at DC frequency and 1kHz achieves -107 and -71dB respectively at 9.0V supply voltage.

Abstract: A capacitor-free CMOS low-noise, low-dropout (LDO) regulator for Micro-accelerometer is presented. Noise performance of the regulator is studied from a theoretical point of view and a chopper stabilized error amplifier is designed to minimize output noise. By adopting pole-zero frequency compensation technique, the proposed LDO regulator, which is independent of an off-chip capacitor, provides high closed-loop stability when the load current is switched by micro-accelerometer. The proposed LDO is designed and fabricated on a 2μm CMOS process. From the simulation results, it shows that the line regulation is 3.5mV/V and the load regulation is 0.33mV/mA when the load current changes from 0 to 30 mA. The experimental results show that the output noise of the regulator is less than 180nV/sqrt(Hz) at low frequency