Series in Microelectronics

edited by Wolfgang Fichtner
Qiuting Huang
Heinz Jäckel
Hans Melchior
George S. Moschytz
Gerhard Tröster

This thesis describes the design and implementation of single-chip low-power biomedical systems for a novel generation of medical devices. Mixed-signal systems-on-a-chip (SoC) have been designed for operation and control in implanted ventricular assist pumps and for implanted blood pressure sensors. Finally, a specific market analysis has been performed prior to the development of a novel communication principle using the human body itself as a data bus. The first SoC described contains a 10 mW 2-channel eddy-current sensing device for 2D magnetic bearing control, which is part of a ventricular assist pump. Power consumption has been reduced by more than a factor of 15 and the accuracy of the position measurement has been improved from 8 to 10 bit through a new excite and readout concept. A micro-transponder has been designed for an implanted blood pressure sensor applying passive telemetry for batteryless operation. Although it drives a low-ohmic sensor, the whole system including data acquisition and RF communication has been the first of its kind consuming less than 500 micro-W. The last system decribes a novel communication approach which makes use of the dielectric characteristics of human tissue. Signals can be transmitted through the human body via galvanic coupling of AC currents in the micro A range. A simplified engineering model has been developed for the communication channel. The principle of operation has been successfully tested with a digital ECG demonstrator.