Implantable medical device incorporating performance based adjustable

Abstract

A method or apparatus for conserving power in an implantable medical device (IMD) of the type having at least one IC powered by a battery wherein, in each such IC, a voltage dependent oscillator for providing oscillator output signals at an oscillation frequency dependent upon applied supply voltage to the IC is incorporated into the IC. The voltage dependent oscillator oscillates at a frequency that is characteristic of the switching speed of all logic circuitry on the IC die that can be attained with the applied supply voltage. The applied supply voltage is regulated so that the oscillation frequency is maintained at no less than a target or desired oscillation frequency or within a desired oscillation frequency range. The power supply voltage that is applied to the IC is based directly on the performance of all logic circuitry of the IC. In order to provide the comparison function, the oscillator output signals are counted, and the oscillator output signal count accumulated over a predetermined number of system clock signals is compared to a target count that is correlated to the desired oscillation frequency. The counts are compared, and the supply voltage is adjusted upward or downward or is maintained the same dependent upon whether the oscillator output signal count falls below or rises above or is equal to the target count, respectively. The supply voltage adjustment is preferably achieved employing a digitally controlled power supply by calculating a digital voltage from the comparison of the oscillator output signal count to the target count, and storing the digital voltage in a register of the power supply.