lm9074ep National Semiconductor Corporation, lm9074ep Datasheet - Page 9

• Manufacturer Part Number: lm9074ep
• Description: Enhanced Plastic System Voltage Regulator With Keep-alive On/off Control
• Manufacturer: National Semiconductor Corporation

Application Information
MICROPROCESSOR SYSTEM REGULATOR WITH
KEEP-ALIVE INTERVAL AT TURN-OFF
The following circuit illustrates a system application utilizing
both of the logic control inputs of the LM9074EP. Closing the
ON/OFF switch powers ON the system. Once powered, the
system controller sets the Keep-Alive line low. The NPN
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transistor is used only to signal the controller that the ON/
OFF switch has been opened and the system is to be turned
OFF. Upon detecting this high level at the ON/OFF Sense
input line, the controller can then perform a power down
routine. The system will remain fully powered until the con-
troller commands total shut down by taking the Keep-Alive
line high. The system then shuts OFF and reverts to a very
low current drain standby condition until switched back on.
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