lm9072 National Semiconductor Corporation, lm9072 Datasheet - Page 6

• Manufacturer Part Number: lm9072
• Description: Dual Tracking Low-dropout System Regulator
• Manufacturer: National Semiconductor Corporation

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Application Information
PIN DESCRIPTION AND FUNCTIONALITY
The LM9072 is a precision dual tracking voltage regulator
optimized for use in powertrain module applications but will
also find use in a wide variety of automotive and industrial
applications where precision supply regulation is required in
harsh operating environments. The following will describe
the functionality of each of the package pins.
INPUT VOLTAGE (Pin 3)
The LM9072 has been designed to connect directly to the
ignition or battery supply in automotive applications. For this
type of supply the regulator has been designed to withstand
up to +60V and −45V supply transients such as load dump.
An overvoltage shut down protection scheme turns OFF
both of the regulator outputs should supply transients ex-
MAIN OUTPUT (Pin 9)
The Main Output regulator provides a well controlled (3%
tolerance maximum) 5V supply line with a total load current
ranging up to 350 mA. This relatively high level of output
current is sufficient to provide power to a large number of
load circuits in a variety of module applications.
This output has a short to ground current limit between
500 mA and 1A. The Main output can also withstand a short
circuit to potentials up to 7V.
To maintain stability of this supply line an output bypass
capacitor is required. This capacitor must be at least 6 µF
with an equivalent series resistance (ESR) between 0.3
and 3
The Main Output is sensed for the generation of the system
reset output. Feedback from the Main Output is also used to
control the output voltage of the tracking regulator.
over temperature.
FIGURE 1. Circuit Block Diagram
6
ceed typically +33V to fully protect all load circuitry. This
higher threshold allows normal operation with 24 V
plied to the input as in the event when two batteries are used
to start a vehicle. Protection of the system is also provided
for inadvertent reverse polarity battery connections.
The current drain on the supply line is directly proportional to
the load currents on the two voltage regulators. With no load
current on either output the regulator requires 15 mA maxi-
mum quiescent current for biasing internal circuitry. During
dropout conditions (V
can rise to 50% of the total load current. With less than 4V
applied to the input, internal biasing circuitry shuts OFF.
When switched OFF the regulator can remain connected to
the battery supply with a current drain of less than 100 µA.
TRACKING OUTPUT (Pin 4)
The Tracking Output regulator is a key feature of the
LM9072. This output provides a voltage that directly tracks
the main output voltage within 1.5%. This 80 mA output is
provided to bias sensors and other devices located external
to the main system module.
For providing remote power the Tracking Output is fully
protected against short circuit connections to the battery or
input supply (up to 27V) and to ground. These shorted fault
conditions do not affect the operation of the main supply nor
generate a reset of the system.
The tracking characteristic allows for ratiometric operation of
sensors by providing power that is directly proportional to the
system supply. Similar to the main output a bypass capacitor
is required for stability. This capacitor should also be greater
than 6 µF with an ESR between 0.3
IN
<
5.5V) the additional input current
and 3 .
DS012906-17
DC
ap-