Low-power A/D converter for an implantable medical device and method of use
First Claim
1. A low-power A/D converter for an implantable medical device operating with a main clock frequency, comprising:
- high-frequency oscillator means for generating clock pulses at a predetermined frequency substantially higher than said main clock frequency;
oscillator gating means for enabling said oscillator means for a voltage-dependent variable time interval, said gating means including voltage-controlled monostable means 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 said implantable medical device; and
counter means coupled to said oscillator means for counting clock pulses generated during said variable time interval.
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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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Citations
7 Claims
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1. A low-power A/D converter for an implantable medical device operating with a main clock frequency, comprising:
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high-frequency oscillator means for generating clock pulses at a predetermined frequency substantially higher than said main clock frequency; oscillator gating means for enabling said oscillator means for a voltage-dependent variable time interval, said gating means including voltage-controlled monostable means 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 said implantable medical device; and counter means coupled to said oscillator means for counting clock pulses generated during said variable time interval. - View Dependent Claims (2, 3)
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4. A low-power A/D conversion method for an implantable medical device operating with a main clock frequency, comprising the steps:
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providing an oscillator capable of generating clock pulses at a predetermined frequency substantially higher than said main clock frequency; gating said oscillator on for a voltage-dependent variable time interval, said gating step including generating a gate control pulse having a pulse width corresponding to the value of an analog signal representative of a physiological parameter sensed by said implantable medical device; and counting clock pulses generated by said oscillator during said variable time interval. - View Dependent Claims (5, 6)
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7. A low-power A/D converter for an implantable medical device operating with a main clock frequency, comprising:
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high-frequency oscillator means for generating clock pulses at a predetermined frequency substantially higher than said main clock frequency; oscillator gating means for enabling said oscillator means for a voltage-dependent variable time interval, said gating means including voltage-controlled monostable means 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 said implantable medical device; a crystal-controlled low-frequency clock; a timing controller having a clock input connected to said low-frequency clock, said timing controller including means for supplying a trigger pulse to said voltage-controlled monostable at a predetermined first point in said variable time interval and means for generating an enable pulse at a predetermined second point in said variable time interval; means responsive to said enable pulse for enabling said oscillator means at said second point in said variable time interval; means responsive to said gate control pulse for disabling said oscillator means at the end of said variable time interval; and counter means coupled to said oscillator means for counting clock pulses generated between said second point and the end of said variable time interval.
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Specification