Control Logic Truth Table

ON/OFF

Input

Keep-Alive

Input

Output

Voltage

Reset

Output

Operating Condition

L

X

0V

L

Low quiescent current standby (OFF) condition

↑

X5V

Output turns ON

H

X

5V

H

Normal ON condition

↓

H

0V

L

Output turns OFF

↓

L

5V

H

Output kept ON by Keep-Alive Input

↑

L

5V

H

Output remains ON (or turns ON)

HX

∆V

L

Output pulled out of regulation, reset flag generated

LL

V

L

Output latches 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 er-

roneous 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 immunity to

RFI the output bypass capacitor is important (47 µF is rec-

ommended).

This regulator is suitable for applications where continuous

connection to the battery is required (

Refer to the Typical Ap-

plication Circuit ). ON/OFF control of the regulator and sys-

tem can be accomplished by switching the ON/OFF input to

the battery or ignition supply V

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

DS101305-22

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