The Intersil ICL7673 is a monolithic CMOS battery backup
circuit that offers unique performance advantages over
conventional means of switching to a backup supply. The
ICL7673 is intended as a low-cost solution for the switching
of systems between two power supplies; main and battery
backup. The main application is keep-alive-battery power
switching for use in volatile CMOS RAM memory systems
and real time clocks. In many applications this circuit will
represent a low insertion voltage loss between the supplies
and load. This circuit features low current consumption, wide
operating voltage range, and exceptionally low leakage
between inputs. Logic outputs are provided that can be used
to indicate which supply is connected and can also be used
to increase the power switching capability of the circuit by
driving external PNP transistors.

Features
• Automatically Connects Output to the Greater of Either
Input Supply Voltage
• If Main Power to External Equipment is Lost, Circuit Will
Automatically Connect Battery Backup
• Reconnects Main Power When Restored
• Logic Indicator Signaling Status of Main Power
• Low Impedance Connection Switches
• Low Internal Power Consumption
• Wide Supply Range: . . . . . . . . . . . . . . . . . . . 2.5V to 15V
• Low Leakage Between Inputs
• External Transistors May Be Added if Very Large
Currents Need to Be Switched
• Pb-Free Plus Anneal Available (RoHS Compliant)

Applications
• On Board Battery Backup for Real-Time Clocks,
Timers, or Volatile RAMs
• Over/Under Voltage Detector
• Peak Voltage Detector
• Other Uses:
- Portable Instruments, Portable Telephones, Line
Operated Equipment