A battery voltage measuring circuit for an implantable cardiac device is presented. Since the usable battery voltage for the device is limited to an upper range of voltages, the need for measuring lower voltages at which the battery is approaching end of life is of no use. The disclosed invention allows for the measurement of a selectable upper range of battery levels that can be chosen without using a level shifting device such as a zener diode. Multiple voltage ranges with associated measurement resolutions can be achieved without using high current zener diode implementations. This allows for a trade-off between measurement range and resolution while resulting in a lower power and more accurate measurement circuit. Conventional zener diode implementations only allow for a single measurement range and are prone to non-linear error as the voltage measurement range increases.
