Power Failure Detection Trigger Memory Saving

Sometimes the power goes down and we unable to save memory content. When the power goer down, the memory save circuit can be used to save memory content. This is a very useful circuit because the AC line dropout detection is not worthy. The difference of dropout voltage from two regulators is a basic of this circuit. This circuit uses two regulators, LT1020 and LT1086. The LT1020 is used to drive the memory section and the main system is supplied by LT1086. Here is the schematic diagram of the  circuit:

This circuit is powered by a battery or filter capacitor. When the input power down, then the LT1086 drops out. So the onboard auxiliary comparator of LT1020 detect that action and goes low. If this thing happens, the memory section will store data. If the dropout is extremely low, the memory power is maintained by the LT1020 regulator  output. The falling time of this circuit is about 50ms. [Circuit’s schematic diagram source: Linear Technology]