Abstract: A voltage and current reference circuit (11) having a low temperature coefficient is provided. The voltage and current reference circuit (11) minimizes component count to reduce area on an integrated circuit die. A bandgap voltage reference (12) produces a low temperature coefficient voltage. A voltage follower (13) is coupled to the bandgap voltage reference (12) that produces a reference voltage corresponding to a bandgap voltage. A temperature variant current from the bandgap voltage reference (12) is mirrored and provided to a first electrode of the voltage follower (13). A resistor (R4) is coupled between a power supply terminal and a second electrode of the voltage follower (13). The resistance of the resistor (R4) is selected to generate a current that cancels temperature dependencies of the temperature variant current. A current mirror circuit (14) receives a remaining portion of the temperature variant current and outputs a low temperature coefficient current.

Abstract: A pulsed battery charger circuit (11) for charging a battery (28). A control circuit (17) is responsive to a sense circuit (16) that monitors the battery voltage. The control circuit (17) pulses a first current source (25) or a second current source (20). An amplifier (14) is responsive to the first (25) and second (20) current sources for generating first and second predetermined voltages between a drive output (12) and a sense input (13). The first current source (25) is pulsed when the sense circuit (16) senses the battery voltage to be less than a first threshold voltage. The second current source (20) is pulsed when the sense circuit (16) senses the battery voltage to be greater than the first threshold voltage. Both the first (25) and second (20) current sources are disabled when the sense circuit (16) senses the battery voltage to be greater than a second threshold voltage.

Abstract: A battery charger status monitor circuit (40) for monitoring the status of a battery (12) charged with current pulses. The current pulses charging the battery (12) are reduced in frequency and duty cycle as the battery approaches a fully charged condition. By monitoring the number of current pulses charging the battery within a predetermined time period, the charge status of the battery (12) is determined. If no pulses are detected within the predetermined time period, the battery (12) is fully charged. A counter (47) is incremented by a clock signal. A charge signal resets the counter (47). The charge signal corresponds to the current pulses charging the battery. If the counter (47) reaches a predetermined count, the clock and charge signals are disabled. Reaching the predetermined count before resetting indicates the battery (12) is fully charged. When the counter is below the predetermined count, the battery (12) is being charged.