LM9071
Low-Dropout System Voltage Regulator with Delayed
Reset
General Description
The LM9071 is a 5V, 250 mA low-dropout voltage regulator.
The regulator features an active low delayed reset output
flag which can be used to reset a microprocessor system on
turn-ON and in the event that the regulator output falls out of
regulation for any reason. An external capacitor programs a
delay time interval before the reset output can return high.
Designed for automotive application the LM9071 contains a
variety of protection features such as reverse battery,
over-voltage shutdown, thermal shutdown, input transient
protection and a wide operating temperature range.
Design techniques have been employed to allow the regula-
tor to remain operational and not generate false reset signals
when subjected to high levels of RF energy (300V/m from
2 MHz to 400 MHz).
Features
n
Automotive application reliability
n
3% output voltage tolerance
n
Insensitive to radiated RFI
n
Dropout voltage less than 800 mV with 250 mA output
current
n
Externally programmed reset delay interval
n
Thermal shutdown
n
Short circuit protection
n
Reverse battery protection
n
Wide operating temperature range -40C to +125C
n
TO-220 and TO-263 power surface mount power
packages
n
Pin for pin compatible with the LM2927, L4947 and
TLE4260
Typical Application and Connection Diagrams
(Top View)
DS012832-1
5-Lead TO-220 Package
DS012832-2
Order Number LM9071T
See NS Package Number T05A
5-Lead TO-220 Package
DS012832-3
Order Number LM9071T/Flow LB03
See NS Package Number T05D
5-Lead TO-263 Surface Mount Package
DS012832-4
Tab and Backside metal on all packages internally connected to ground.
Order Number LM9071S
See NS Package Number TS5B
December 1999
LM9071
Low-Dropout
System
V
oltage
Regulator
with
Delayed
Reset
1999 National Semiconductor Corporation
DS012832
www.national.com
Absolute Maximum Ratings
(Note 1)
DC Input Voltage
-26V to +26V
Positive Input Transient (t
<
100 ms)
60V
Negative Input Transient (t
<
1 ms)
-50V
Reset Output Sink Current
5 mA
Power Dissipation
Internally Limited
Junction Temperature
150C
ESD Susceptibility (Note 2)
12 kV, 2 kV
Lead Temperature
(Soldering, 10 seconds)
260C
Storage Temperature
-50C to +150C
Operating Ratings
(Note 1)
Input Voltage
6V to 26V
Ambient Temperature
-40C to +125C
jc, TO-220, TO-263 Packages
3C/W
ja, TO-220, TO-263 Packages
43C/W
Electrical Characteristics
The following specifications apply for V
CC
= 6V to 26V, -40C
T
A
+125C, unless otherwise specified. C
OUT
= 47 Fd with
an ESR
<
3
. C
IN
=1 Fd.
Symbol
Parameter
Conditions
Min
Max
Units
REGULATOR OUTPUT
V
OUT
Output Voltage
5 mA
I
OUT
250 mA
4.85
5.15
V
V
OUT
Line
Line Regulation
I
OUT
= 5 mA, 9V
V
IN
16.5V
25
mV
I
OUT
= 250 mA
50
mV
V
OUT
Load
Load Regulation
V
IN
= 14.4V, 5 mA
I
OUT
250 mA
60
mV
Iq
Quiescent Current
I
OUT
= 5 mA
4
mA
I
OUT
= 250 mA, V
IN
8V
25
mA
I
OUT
= 5 mA, V
IN
= 5V
10
mA
I
OUT
= 250 mA, V
IN
= 6V
50
mA
Vdo
Dropout Voltage
I
OUT
= 5 mA
300
mV
I
OUT
= 250 mA
800
mV
Isc
Short Circuit Current
R
L
= 1
0.35
1.5
A
RR
Ripple Rejection
F
ripple
= 120 Hz, V
ripple
= 1 Vrms
I
OUT
= 50 mA
60
dB
OVthr
Overvoltage Shutdown
Threshold
27
V
V
O
Transient
V
OUT
during Transients
V
IN
Peak
60V, R
L
= 100
,
= 100 ms
7
V
RESET OUTPUT
Vth
Threshold Voltage
V
OUT
Required to Generate a Reset
Output
4.8V
V
OUT
5.2V
-300
-500
mV
Vlow
Reset Output Low Voltage
Isink = 1.6 mA, V
OUT
>
3.2V
0.4
V
1.4V
V
OUT
3.2V
0.8
V
Vhigh
Reset Output High Voltage
0.8
V
OUT
V
t
delay
Delay Time
Cdelay = 100 mFd
7.6
35
ms
Idelay
Charging Current for Cdelay
10
30
A
Rpu
Internal Pull-up Resistance
12
80
k
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and conditions, see the Electrical Characteristics.
Note 2: All pins will survive an ESD impulse of
2000V using the human body model of 100 pF discharged through a 1.5 k
resistor. In addition the input voltage
pin will withstand ten pulses of
12 kV from a 150 pF capacitor discharged through a 560
resistor when bypassed with a 22 nF, 100V capacitor.
LM9071
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2
Typical Performance Characteristics
(T
A
= 25C unless indicated otherwise)
Turn ON Characteristics
DS012832-5
Turn OFF Characteristics
DS012832-6
Normalized Output Voltage
vs Temperature
DS012832-7
Output Voltage at
Input Voltage Extremes
DS012832-8
Quiescent Current vs
Input Voltage
DS012832-9
Short Circuit Current
vs Temperature
DS012832-10
Dropout Voltage vs
Temperature
DS012832-11
Reset Delay Time
vs Temperature
DS012832-12
Output Capacitor ESR
DS012832-13
LM9071
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3
Typical Performance Characteristics
(T
A
= 25C unless indicated otherwise) (Continued)
Reset Operation and Protection Features
Block Diagram
Maximum Power Dissipation
(TO-220 Package)
DS012832-14
Maximum Power Dissipation
(TO-263 Package)
DS012832-15
DS012832-16
DS012832-17
LM9071
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4
Application Hints
The LM9071 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 LM9071 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 F is rec-
ommended).
An output bypass capacitor of at least 10 F is required for
stability (47 F is recommended). The ESR of this capacitor
should be less than 3
. An input capacitor of 1 F or larger
is recommended to improve line transient and noise perfor-
mance.
Conventional load dump protection is built in to withstand up
to +60V and -50V transients. Protection against reverse po-
larity battery connections is also built in. With a reversed bat-
tery connection the output of the LM9071 will not go more
negative than one diode drop below ground. This will prevent
damage to any of the 5V load circuits.
RESET FLAG
Excessive loading of the output to the point where the output
voltage drops by 300 mV to 500 mV will signal a reset flag to
the micro. This will warn of a V
CC
supply that may produce
unpredictable operation of the system. On power-up and re-
covery from a fault condition the delay capacitor is used to
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 delay time interval can
be estimated by the following equation:
INPUT STABILITY
Low dropout voltage regulators which utilize a PNP power
transistor usually exhibit a large increase in current when in
dropout (V
IN
<
5.5V). This increase is caused by the satura-
tion characteristics (
reduction) of the PNP transistor. To
significantly minimize this increase in current the LM9071
detects when the PNP enters saturation and reduces the op-
erating current.
This reduction in input current can create a stability problem
in applications with higher load current (
>
100 mA) where
the input voltage is applied through a long length of wire,
which in effect adds a significant amount of inductance in se-
ries with the input. The drop in input current may create a
positive input voltage transient which may take the PNP out
of saturation. If the input voltage is held constant at the
threshold where the PNP is going in and out of saturation, an
oscillation may be created.
This is only observed where a large series inductance is
present in the input supply line and when the rise and fall
time of the input supply is very slow. If the application and re-
moval of the input voltage changes at a rate greater than
500 mV/s it will move through the dropout region of the
regulator (V
IN
of 3V to 5.5V) too quickly for an oscillation to
be established.
LM9071
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