This circuit can be used as a low cost SRAM and Microcontroller or Microprocessor Battery Backup. All the diodes are 1N4148, The diodes prevent battery discharge back to power source. D8 gives a one way path to charge Battery thru R13 which limits current. D4 ensures a one way path of supply to chip when power is present. D5 is backup supply on power failure.
Microcontroller in Process Control
The chip a real time clock, RAM or Processor can be put to standby or sleep on power failure. If it is not a smart chip then make sure on power failure all outputs of chip are high impedance or floating. do not use any pullups or resistor dividers to Vbat, which is the supply to chip. There should be no leakage path from Vbat, decoupling cap of chip must be plastic.
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