Battery circuit for an integrated circuit (IC) memory card

Claim 1

A battery circuit incorporated in an integrated circuit (IC) memory card comprising: a power control circuit having a ground input, first and second power inputs, and a power output for connection to a power input of a memory chip; an external power supply line and a ground line connected to the first power input and the ground input of said power control circuit, respectively, for supplying power from outside of said card to said power control circuit; and a data backup battery having negative and positive terminals connected to the ground input and the second power input of said power control circuit, respectively, said battery producing a voltage at the positive terminal, said power control circuit including an active switching device connected between the second power input and the power output and coupled to the first power input, said active switching device preventing a current flowing into the first power input from flowing out of the second power input into said data backup battery when the voltage applied to said external power supply line is higher than the voltage of said battery, electrically connecting said battery for supplying the voltage of said battery to said power output in response to a voltage greater than the voltage of said battery applied to said power output via said external power supply line and electrically connecting said battery to said power output when the battery is connected for supplying the voltage of said battery to said power output and the voltage of said battery is higher than the voltage of said external power supply line, and electrically disconnecting said battery from said power output in response to a control signal supplied from outside of said card via said external power supply line.