BATTERY BACK-UP CIRCUIT FOR MEMORY

摘要

PURPOSE:To measure the battery voltage in a real load state by switching the memory supply voltage to the battery side just for the time required for measurement of the voltage while a main power supply is working. CONSTITUTION:When the battery voltage Vb is measured, a processor 5 outputs a switch control command SC to a switch circuit 6 while a main power supply is working. The command SC is equal to a high-level signal having a fixed time width. Thus the switch 6 switches a power supply line led to a memory 7 to the side of a battery 3 as long as said high-level signal is supplied. Furthermore the processor 5 issues a voltage measurement command VMC while the power supply line is switched. A battery voltage measuring circuit 4 receives the command VMC and measures the voltage Vb at this time point. Thus the circuit 6 is switched for a fixed time while the power supply is kept ON and therefore the voltage Vb is measured at the real load.