lm9074mx National Semiconductor Corporation, lm9074mx Datasheet - Page 8

• Manufacturer Part Number: lm9074mx
• Description: System Voltage Regulator With Keep-alive On/off
• Manufacturer: National Semiconductor Corporation

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Application Information
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:
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/
(Continued)
8
For a C
the typical delay time will be:
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.
t
DELAY
DELAY
t
DELAY
value of 0.1 µF and a typical I
= ((3.4V x 0.1 µF) / 12 µA)) = 28.3 ms
= ((3.4V x C
DELAY
) / I
DELAY
10130526
DELAY
))
of 12 µA,