Patent ID: 6967468
Filing Date: 2005-11-22
Classification: H02J

Abstract:
1. An apparatus comprises: a protection circuit to provide overvoltage protection and backflow current protection when an external voltage is received through a data transfer link and used to charge a battery, in which the external voltage exceeds nominal value of a rail voltage supplied by the battery, the protection circuit to accept the external voltage, but to ensure that node-to-node potential on circuit components do not exceed a specified value when the external voltage is used to charge the battery and to prevent backflow current from the battery to the data transfer link when the external voltage drops below battery voltage; a biasing circuit to bias the protection circuit; and a switching circuit to change the bias applied by the biasing circuit to selectively switch a mode of operation of the protection circuit between the overvoltage protection and the backflow current protection, wherein the protection circuit uses a floating well transistor, in which its gate is to be biased by the switching circuit when in the backflow current protection mode of operation, to turn off the floating well transistor to eliminate a current path from the battery to a line of the data transfer link that supplies the external voltage.