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 LM9074. Closing the

ON/OFF switch powers ON the system. Once powered, the

system controller sets the Keep-Alive line low. The NPN

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 in-

put line, the controller can then perform a power down rou-

tine. The system will remain fully powered until the controller

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.

DS101305-26

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