| Since the initial development of the implantable cardiac pacemaker over thirty-five years ago, the field of biomedical engineering has provided many different implantable devices to the medical profession for the treatment of various anomalies. These advances have been possible largely because of the efforts of inventors and entrepreneurs who established an important new industry for biomedical implantable devices. Today, implantable cardioverter and defibrillators, drug delivery systems, neuromuscular stimulators, bone growth stimulators, and other implantable devices are in clinical use and make possible the treatment of a variety of diseases. They save lives and improve the quality of life of many other patients suffering from various medical conditions.;The remarkable progress in the microelectronic integration technology, together with the considerable advancement and maturity of clinical treatment techniques using electrical stimulation, have accelerated the advent of a new generation of implantable devices. They are multiprogrammable and incorporate adjustment and control feedback loops in conjunction with various types of sensors to capture biological and clinical information. The new generations of implantable electronic circuits are fabricated using VLSI technology and incorporate high performance digital and analog building blocks. Functional verification of mixed-signal VLSI circuits is very complicated, unless design for testability (DFT) is considered early during the design procedure. Higher are the complexity and the integration level of an implantable microelectronic circuit, higher is the probability of a fault in the implant. Therefore, the reliability of the new generation of implantable systems becomes more critical and must receive a special attention. Otherwise, the lack of reliability may lead the physicians to refuse using sophisticated implantable systems in clinical treatments.;The main objective of this thesis is to provide simple and effective methods to design high reliability biomedical implantable devices. Therefore, different aspects of design for reliability are considered. To achieve secure implantable systems, we have focused our efforts in the following research areas. (1) Development of simple and effective methods for built-in self-test (BIST) of mixed-signal circuits and especially implantable systems. As the fault in the bioelectronic interface of implantable systems is an important reason of the implant upset, some techniques to monitor the state of electrodes, leads, and interelectrode tissue are also introduced. (2) Development of techniques to predict the occurrence of eventual faults in electronic systems. Knowing that excessive chip temperatures cause its deterioration, temperature sensors have been integrated with the microelectronic circuit to monitor its thermal state. An on-line power dissipation measurement technique has been also proposed which allow to predict the implant's battery life-time. (3) Development of a new secure communication protocol dedicated to implantable systems having multiple means of error correction capability. This communication protocol can be used for programming the implant and telemetering its parameters as well as the clinical state of the patient. The results obtained during the research conducted in this thesis will allow the biomedical implantable device to be more reliable and to profit from the remarkable progress in the integration technology of microelectronic circuits. Further developments are necessary to render the implants more reliable, especially in the field of fault tolerant electronic circuit design. |
