Patent ID: 8222904

Claim:
A battery end-point voltage detection method for an electronic device, including a battery, at least first and second comparators, a nonvolatile memory, and an electronic circuit driven by the voltage of the battery, comprising: supplying a voltage of an external power supply to the inputs of the first and second comparators; using the voltage of the external power supply to measure first and second reference voltages of the first and second comparators, respectively; storing the measured first and second reference voltages in said non-volatile memory; supplying an output voltage of the battery to inputs of the first and second comparators; detecting in the first comparator, a first detection time when the input voltage from the battery becomes lower than the first reference voltage; detecting in the second comparator, a second detection time when the input voltage from the battery becomes lower than the second reference voltage; and determining time information regarding the end-point voltage of the battery based on the first and second detection times as well as the measured first and second reference voltages.