Method and circuit for supplying memory IC power

A method for supplying power to an IC memory, said circuit including a reserve power supply including primary and secondary batteries, a secondary battery charging circuit for charging said secondary battery, and a primary and secondary battery backup circuit for connecting said primary and secondary batteries to the IC memory, said method comprising the steps of:

• providing power and operating voltage from said secondary battery to said IC memory along a first electrical path when primary power to said IC memory is discontinued;
• providing power and operating voltage from said primary battery to said IC memory along a second electrical path and in parallel providing power and operating voltage from said secondary battery to said IC memory along the first electrical path when primary power to said IC is discontinued, and voltage supplied by said secondary battery falls below a voltage level supplied by said primary battery;
• providing power and operating voltage from said primary battery and said secondary battery along a third electrical path to said IC memory when primary power to said IC is discontinued and the voltage supplied by said primary and secondary batteries falls below a reference level, wherein the primary and second batteries are connected in series in the third electrical path.

A circuit for supplying power to an IC memory, said circuit including a reserve power supply including primary and secondary batteries, a second battery charging circuit for charging said secondary battery, and a primary and secondary battery backup circuit for connecting said primary and secondary batteries to the IC memory, the circuit further comprising:

• a first electrical path for providing power and operating voltage to said IC memory from said secondary battery when primary power to said IC memory is discontinued;
• a second electrical path for providing power and operating voltage to said IC memory from said primary battery when primary power to said IC memory is discontinued, and voltage supplied by said secondary battery falls below a voltage level supplied by said primary battery;
• a third electrical path for providing power and operating voltage to said IC memory from both of said primary and secondary batteries in series when primary power to said IC memory is discontinued and the voltage supplied by said primary and second batteries falls below a reference level.

A method for providing power to a device including memory that receives a primary voltage from a primary power supply that may be connected and disconnected, comprising the steps of:

• coupling first and second batteries to the device if the primary power supply is disconnected, wherein the first and second batteries are coupled to the device in parallel if voltage provided to the device by the parallely coupled first and second batteries is not below a reference voltage level;
• and coupling the first and second batteries to the device in series if the voltage provided to the device by the parallely coupled first and second batteries is below the reference voltage level.