Charger control circuit for a portable electronic device, the charger control circuit comprising a first charger terminal and a system terminal and being configured to - assign a voltage applied at the first charger terminal to one of at least three voltage ranges by performing at least one voltage comparison; - determine and distinguish, based on the assignment, whether an external charger or a secondary battery (SBAT) is connected to the first charger terminal; and - depending on a predetermined operating state of the first charger terminal - supply power from the secondary battery (SBAT) to the portable electronic device via the system terminal, when the secondary battery (SBAT) is connected to the first charger terminal and the operating state of the first charger terminal corresponds to an enabling of the first charger terminal; - supply power from the external charger to the portable electronic device via the system terminal, when the external charger is connected to the first charger terminal and the operating state of the first charger terminal corresponds to an enabling of the first charger terminal; and - supply no power from the secondary battery (SBAT) or from the external charger to the portable electronic device, if the operating state of the first charger terminal corresponds to a disabling of the first charger terminal; wherein a first voltage range of the at least three voltage ranges corresponds to voltage values below a first threshold value, a second voltage range of the at least three voltage ranges corresponds to voltage values above the first threshold value and below a second threshold value, and a third voltage range of the at least three voltage ranges corresponds to voltage values above the second threshold value; wherein the second threshold value is greater than the first threshold value; and wherein the first threshold value corresponds to a minimum battery detection voltage and the second threshold value corresponds to a minimum charger detection voltage. - assign a voltage applied at the first charger terminal to one of at least three voltage ranges by performing at least one voltage comparison; - determine and distinguish, based on the assignment, whether an external charger or a secondary battery (SBAT) is connected to the first charger terminal; and - depending on a predetermined operating state of the first charger terminal - supply power from the secondary battery (SBAT) to the portable electronic device via the system terminal, when the secondary battery (SBAT) is connected to the first charger terminal and the operating state of the first charger terminal corresponds to an enabling of the first charger terminal; - supply power from the external charger to the portable electronic device via the system terminal, when the external charger is connected to the first charger terminal and the operating state of the first charger terminal corresponds to an enabling of the first charger terminal; and - supply no power from the secondary battery (SBAT) or from the external charger to the portable electronic device, if the operating state of the first charger terminal corresponds to a disabling of the first charger terminal; - supply power from the secondary battery (SBAT) to the portable electronic device via the system terminal, when the secondary battery (SBAT) is connected to the first charger terminal and the operating state of the first charger terminal corresponds to an enabling of the first charger terminal; - supply power from the external charger to the portable electronic device via the system terminal, when the external charger is connected to the first charger terminal and the operating state of the first charger terminal corresponds to an enabling of the first charger terminal; and - supply no power from the secondary battery (SBAT) or from the external charger to the portable electronic device, if the operating state of the first charger terminal corresponds to a disabling of the first charger terminal;