CMOS Delta Sigma Magnetic to Digital Converter

• Main Authors: Shr-Lung Chen, 陳仕龍
• Other Authors: Shen-Iuan Liu
• Format: Others
• Language: en_US
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/89670513080719273701

碩士 === 國立臺灣大學 === 電機工程學研究所 === 89 === In this thesis, we have proposed several magnetic to digital converters designed with MAGFET, and we have successfully transferred the magnetic signal into frequency domain, time domain, and voltage domain respectively. These application circuits are implemented in UMC 0.5mm DPDM CMOS process and SHARP 0.35mm DPDM CMOS process. In chapter2, the “double MOSFET method” has been applied to implement the linear resistor pairs in MOP, and this gives the possibility of implementing a fully integrated magnetic sensor interface. In chapter3, a magnetically controlled ring oscillator has been proposed. In particular, it exhibits the highest sensitivity/power ratio reported to date for a silicon magnetic field sensor based on oscillator. Another magnetic to pulse width digitizer has also been realized, which can reach a very small equivalent resolution. After off-line calibration, the offset can be reduced and gain error can be further minimized. Transferring the magnetic signal to frequency and time domain pave the way for the low voltage operation in the future. In chapter 4, We combined the MOP with the integrator of the modulator in the first order MDC, thus saving power and area because one opamp is spared. Combining this method with the pseudo two path technique, we presented a very compact second order MDC system using only opamp for low cost applications. In chapter5, the MAGFET offset canceling technique and differencing sampling technique are applied along with the design of MOP and integrator. The goal of reduced offset and gain factor enhancement are achieved. To sum up, we demonstrated the potential of oversampling techniques (in particular sigma-delta modulators and incremental A/D converters) for implementing very flexible, robust and performant sensor interface circuits. The measurement results have verified the correctness and feasibility of designed circuits. Such MDCs have the potential for low cost magnetic sensor applications.