Patent ID: 6339315
Filing Date: 2002-01-15
Classification: G01R

Abstract:
A charge counter for monitoring the charge and discharge current of a battery of an electronic device, the charge counter comprising:a battery current sensing resistor; a differential amplifier having inputs coupled to terminals of the battery current sensing resistor; a resettable integrator of an output signal of the differential amplifier, and including a capacitor; a first comparator of the output signal of the integrator for generating a logic charge interrupt signal; a second comparator of the output signal of the integrator for generating a logic discharge interrupt signal; a logic circuit for receiving the logic charge interrupt signal and the logic discharge interrupt signal; a switch, which is momentarily closed by the logic circuit at every transition of the logic charge interrupt signal and the logic discharge interrupt signal, for discharging the capacitor of the integrator; a processor for receiving the logic charge interrupt signal and the logic discharge interrupt signal to monitor the state of charge of the battery; a timer measuring the time elapsing from the start of a new integration ramp and the switching instant of either one of the first and second comparators; and a nonvolatile memory containing information corresponding to a time interval integration of an offset of the differential amplifier up to the switching instant of either one of the first and second comparators, the offset comprising a short-circuiting of the inputs of the differential amplifier during a trimming step and the information including a sign bit depending on which one of the first and second comparators was switched; the processor incrementing or decrementing the computation of the logic charge interrupt signal and the logic discharge interrupt signal depending on the sign bit of the offset at an expiration of each time interval of integration of the offset stored in the memory.