ASIC design of programmable multi-channel AC current generators for bio-impedance system

• Main Authors: Yi-Hsiu Chen, 陳怡秀
• Other Authors: Kuo-Sheng cheng
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/22853201894535370326

碩士 === 國立成功大學 === 醫學工程研究所碩博士班 === 91 === In this study, the multi-channel current generators are designed and developed for bio-impedance system. According to the characteristics of tissue impedance, through injecting AC currents from periphery, and then measuring voltages, the impedance image of tissue can be obtained using image reconstruction algorithm. There are two major properties of current generator: (1) the amplitude of the current generator must be stable without significant loading effect; (2) the property of each current generator must be as similar as possible. In past study, the current generator is made of discrete components. The disadvantage of the traditional analog device is the imprecision of the values of resistances and capacitors. It needs to be fine-tuned to assure the channels with same specification. It is also big in volume. The purpose of the study is to design a multi-channel programmable current generators in ASIC. For single channel, the system consists of voltage controlled current source (VCCS) and digital to analog converter (DAC). The VCCS with feedback network is used to make current stable. The DAC converts the carrier provided from digital oscillator to AC voltage for VCCS. Its amplitude is set by digital input. For the multi-channel current generators, the DAC must be shared with every channel VCCS. It needs to add an analog storage and analog multiplier. In this study, all of the functional blocks have been verified by using Hspice based on the parameters of TSMC 0.25μm CMOS process.