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Abstract

A low-power A/D converter for an implantable medical device. The converter includes a high-frequency oscillator capable of generating clock pulses at a frequency substantially higher than the main clock frequency of the implantable device, and an oscillator-gating circuit for enabling the oscillator for a voltage-dependent variable time interval. The gating circuit includes a voltage-controlled monostable multivibrator for generating a gate control pulse having a pulse width corresponding to the value of an analog signal representative of a physiological parameter sensed by the implantable device. A timing controller, which operates at a low frequency under control of a crystal-controlled clock, supplies a trigger pulse to the voltage-controlled monostable at a predetermined first point in the variable time interval and generates an enable pulse at a predetermined second point in the variable time interval. In response to the enable pulse, the A/D converter enables the oscillator at the second point and, in response to the gate control pulse, disables the oscillator at the end of the variable time interval. A counter coupled to the oscillator counts the clock pulses generated between the second point and the end of the variable time interval.

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First Claim