VERTICAL OPTIMIZATION PROCEDURE FOR AN INTEGRATED MICROPOWER SIGNAL PREPROCESSOR

The need for low-power operation is characteristic of all electronic measurement systems that transmit physiological data across the intact skin. Custom integrated circuits and hybrid microcircuit-assembly techniques leave battery volume (or power drain) as the limiting factor for implanted-system lifetime and animal-model size.; First-generation totally implantable CW doppler blood flowmeters telemeter doppler-shifted signals having a 40 kHz bandwidth. External electronics are then used to convert this information into a flow signal with a maximum bandwidth of approximately 100 Hz.; A vertically optimized system-circuit-device procedure utilizes a digital data link for telemetry to reduce flowmeter-transmitter power consumption. In this CW doppler ultrasonic flowmeter, a potential 400:1 reduction in FM transmitter power is possible through additional signal preprocessing in the implanted package. A 10:1 savings in transmitter power drain is realized by a novel preprocessor developed to encode and telemeter pulsed digital data rather than doppler signals. An external decoder and D/A converter complete the reduced-power data link.; Key to successful preprocessor implementation is an optimized micropower linear-compatible I('2)L technology. Stratified epitaxy, non-abutting N('+) collars, and a PNP down-driving circuit for stacked I('2)L are innovations of general application that enable the realization of a custom micropower integrated preprocessor chip without increased fabrication complexity compared to conventional analog-compatible biopolar process schedules.