LM9074 Datasheet, PDF (7/12 Pages) National Semiconductor (TI) – System Voltage Regulator with Keep-Alive ON/OFF

Block Diagram
Application Information
The LM9074 voltage regulator has been optimized for use in
microprocessor based automotive systems. Several unique
design features have been incorporated to address many
FMEA (Failure Mode Effects Analysis) concerns for fail-safe
system performance.
FAULT TOLERANT FEATURES
While not specifically guaranteed due to production testing
limitations, the LM9074 has been tested and shown to con-
tinue to provide a regulated output and, not generate an
erroneous system reset signal while subjected to high levels
of RF electric field energy (up to 300 V/m signal strength
over a 2 MHz to 400 MHz frequency range). This is very
important in vehicle safety related applications where the
system must continue to operate normally. To maintain this
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immunity to RFI the output bypass capacitor is important
(47 µF is recommended).
This regulator is suitable for applications where continuous
connection to the battery is required (Refer to the Typical
Application Circuit ). ON/OFF control of the regulator and
system can be accomplished by switching the ON/OFF input
to the battery or ignition supply V_IN supply through a SPST
switch. If this input becomes open circuited, an internal
pull-down resistor ensures that the regulator turns OFF.
When the regulator is switched OFF the current load on the
battery drops to less than 60 µA. With the possibility in many
applications for V_IN and the ON/OFF input pins to be con-
nected in a system through long lengths of wire, the ESD
protection of these pins has been increased to 12 kV with the
addition of small input bypass capacitors.
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