hold the micro in a reset condition for a programmable time

interval to allow the system operating voltages and clock to

stabilize before executing code.

The typical delay time interval can be estimated using the

following equation:

t

ForaC

the typical delay time will be:

t

10130526

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

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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