lm9074ep National Semiconductor Corporation, lm9074ep Datasheet - Page 7

• Manufacturer Part Number: lm9074ep
• Description: Enhanced Plastic System Voltage Regulator With Keep-alive On/off Control
• Manufacturer: National Semiconductor Corporation

Block Diagram
Application Information
The LM9074EP 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 LM9074EP has been tested and shown to
continue 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
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
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-
IN
supply through a SPST
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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.
An output bypass capacitor of at least 0.1µF is required for
stability (47 µF is recommended). An input capacitor of 1 µF
or larger is recommended to improve line transient and noise
performance.
With the Keep-Alive input, a system microprocessor has the
ability to keep the regulator ON (with a logic “0” on Keep-
Alive) after the ON/OFF input has been commanded OFF. A
power-down sequence, when system variables are typically
stored in programmable memory, can be executed and take
FIGURE 1. Typical Application Circuit
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