LM3722/LM3723/LM3724
5-Pin Microprocessor Reset Circuits
General Description
The LM3722/LM3723/LM3724 microprocessor supervisory
circuits monitor the power supplies in microprocessor and
digital systems. They provide a reset to the microprocessor
during power-up, power-down, brown-out conditions, and
manual reset.
The LM3722/LM3723/LM3724 asserts a reset signal when-
ever the supply decreases below the factory-programmed
reset threshold for at least 100 ms. The reset signal remains
asserted for 190 ms after V
CC
rises above the threshold.
The LM3722 has an active-low RESET push-pull output. The
LM3723 has an active-high RESET push-pull output. The
LM3724 has an active-low open-drain RESET output.
Three standard reset voltage options are available, suitable
for monitoring 5V, 3.3V, and 2.5V supply voltages. Additional
reset voltages are also available; contact National Semicon-
ductor for details.
With
a
low
supply
current
of
only
6A,
the
LM3722/LM3723/LM3724 are ideal for use in portable equip-
ment. The LM3722/LM3723/LM3724 are available in the
5-pin SOT23 package.
Features
n
Precise monitoring of 2.5V, 3.3V, and 5V supply
voltages
n
Fully specified over temperature
Industrial: -40C to +85C
Extended: -40C to +125C
n
100 ms minimum Power-On Reset pulse width, 190 ms
typical:
Active-Low RESET Output (LM3722)
Active-High RESET Output (LM3723)
Active-Low RESET Open Drain Output (LM3724)
n
Guaranteed RESET Output valid for V
CC
1V
n
Low Supply Current, 6A typical
n
Power supply transient immunity
n
Compatible with MAX811/812 applications
Applications
n
Microprocessor Systems
n
Computers
n
Controllers
n
Intelligent Instruments
n
Portable/Battery-Powered Equipment
Typical Application Circuit
20014401
20014437
Connection Diagram
SOT23-5
20014402
*
( ) are for LM3723
June 2001
LM3722/LM3723/LM3724
5-Pin
Microprocessor
Reset
Circuits
2001 National Semiconductor Corporation
DS200144
www.national.com
Ordering Information
Industrial Temperature Range (-40C to +85C):
Reset
Threshold (V)
LM3722 Supplied as
1000 units, tape & reel
LM3722 Supplied as
3000 units, tape & reel
Package
Top Mark
Package
Type
NSC Package
4.63
LM3722IM5-4.63
LM3722IM5X-4.63
R43B
SOT23-5
MF05A
3.08
LM3722IM5-3.08
LM3722IM5X-3.08
R41B
2.32
LM3722IM5-2.32
LM3722IM5X-2.32
R34B
Reset
Threshold (V)
LM3723 Supplied as
1000 units, tape & reel
LM3723 Supplied as
3000 units, tape & reel
Package
Top Mark
Package
Type
NSC Package
4.63
LM3723IM5-4.63
LM3723IM5X-4.63
R13B
SOT23-5
MF05A
3.08
LM3723IM5-3.08
LM3723IM5X-3.08
R11B
2.32
LM3723IM5-2.32
LM3723IM5X-2.32
R46B
Reset
Threshold (V)
LM3724 Supplied as
1000 units, tape & reel
LM3724 Supplied as
3000 units, tape & reel
Package
Top Mark
Package
Type
NSC Package
4.63
LM3724IM5-4.63
LM3724IM5X-4.63
R55B
SOT23-5
MF05A
3.08
LM3724IM5-3.08
LM3724IM5X-3.08
R53B
2.32
LM3724IM5-2.32
LM3724IM5X-2.32
R50B
Extended Temperature Range (-40C to +125C):
Reset
Threshold (V)
LM3722 Supplied as
1000 units, tape & reel
LM3722 Supplied as
3000 units, tape & reel
Package
Top Mark
Package
Type
NSC Package
4.63
LM3722EM5-4.63
LM3722EM5X-4.63
R56B
SOT23-5
MF05A
3.08
LM3722EM5-3.08
LM3722EM5X-3.08
R57B
2.32
LM3722EM5-2.32
LM3722EM5X-2.32
R58B
Reset
Threshold (V)
LM3723 Supplied as
1000 units, tape & reel
LM3723 Supplied as
3000 units, tape & reel
Package
Top Mark
Package
Type
NSC Package
4.63
LM3723EM5-4.63
LM3723EM5X-4.63
R59B
SOT23-5
MF05A
3.08
LM3723EM5-3.08
LM3723EM5X-3.08
R60
2.32
LM3723EM5-2.32
LM3723EM5X-2.32
R61B
Reset
Threshold (V)
LM3724 Supplied as
1000 units, tape & reel
LM3724 Supplied as
3000 units, tape & reel
Package
Top Mark
Package
Type
NSC Package
4.63
LM3724EM5-4.63
LM3724EM5X-4.63
R62B
SOT23-5
MF05A
3.08
LM3724EM5-3.08
LM3724EM5X-3.08
R63B
2.32
LM3724EM5-2.32
LM3724EM5X-2.32
R64B
Custom voltages and improved accuracies are available, subject to minimum orders. Contact your local National Semiconductor Sales Office for information.
LM3722/LM3723/LM3724
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2
Pin Description
PIN
NAME
FUNCTION
1
GND
Ground reference
2
GND
Ground reference, device substrate, connect to ground.
3
RESET
LM3722/LM3724
Active-low output. RESET remains low while V
CC
is below the reset threshold
voltage, and for 190 ms after V
CC
rises above the reset threshold voltage.
RESET
LM3723
Active-high output. RESET remains high while V
CC
is below the reset threshold, and
for 190 ms after V
CC
rises above the reset threshold.
4
MR
Active-low input. Reset is asserted whenever this pin is pulled low and remains
asserted for 190 ms after the MR pin goes high. May be left open.
5
V
CC
Supply Voltage (+5V, +3.3V, or +2.5V, nominal)
Block Diagram
LM3722/LM3723/LM3724 Block Diagram
20014435
LM3722/LM3723/LM3724
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3
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
CC
, MR
-0.3V to 6.0V
RESET, RESET
-0.3V to (V
CC
+ 0.3V)
Input Current, V
CC
Pin
20mA
Output Current, RESET,
RESET Pin
20mA
ESD Rating (Note 2)
2kV
Continuous Power Dissipation (T
A
= +70C)
SOT-23 (Note 3)
320mW
Operating Temperature Range
Industrial:
-40C to +85C
Extended:
-40C to +125C
Maximum Junction Temperature
125C
Storage Temperature Range
-65C to +160C
Lead Temperature
(soldering, 10sec)
+300C
Electrical Characteristics
Typical values are at T
A
= +25C. Limits with standard typeface are for T
A
= +25C, and limits in boldface type apply for the
operating temperature range (-40C to +85C) for LM372_IM5X, and (-40C to +125C) for LM372_EM5X, unless otherwise
noted. (Note 4)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
V
CC
V
CC
Range
1.0
5.5
V
I
CC
Supply Current
(I
LOAD
= 0A)
LM372 _ -4.63
V
CC
= 5.5V
8
15
A
LM372 _ -3.08
V
CC
= 3.6V
7
10
LM372 _ -2.32
V
CC
= 2.5V
6
10
V
TH
Reset Threshold
LM372 _ -4.63
4.54
4.50
4.63
4.72
4.75
V
LM372 _ -3.08
3.03
3.00
3.08
3.14
3.15
LM372 _ -2.32
2.27
2.25
2.32
2.37
2.40
V
TH
Tempco
Reset Threshold
Temperature Coefficient
30
ppm/C
t
RD
V
CC
to Reset Delay (Note 5)
V
CC
= V
TH
to (V
TH
- 100mV)
20
s
t
RP
Reset Active Timeout Period
100
190
560
ms
t
MR
MR Minimum Pulse Width
10
s
t
MD
MR to Reset Propagation
Delay
2
s
MR Glitch Immunity (Note 6)
100
ns
V
IH
MR Input Threshold
V
CC
>
V
TH(MAX)
, LM372_ -4.63
2.3
V
V
IL
0.8
V
IH
V
CC
>
V
TH(MAX)
, LM372_ -3.08, LM372_
-2.32
0.7 V
CC
V
IL
0.25 V
CC
MR Pull-Up Resistance
22
k
V
OL
RESET Output Voltage Low
(LM3722)
V
CC
= V
TH
min, I
SINK
= 1.2mA,
(LM3722-2.32/3.08)
0.3
V
V
CC
= V
TH
min, I
SINK
= 3.2mA,
(LM3722-4.63)
0.4
V
CC
>
1V, I
SINK
= 50A
0.3
V
OH
RESET Output Voltage High
(LM3722)
V
CC
>
V
TH
max, I
SOURCE
= 500A,
(LM3722-2.32/3.08)
0.8V
CC
V
V
CC
>
V
TH
max, I
SOURCE
= 800A,
(LM3722-4.63)
V
CC
-1.5
V
OL
RESET Output Voltage Low
(LM3723)
V
CC
= V
TH
max, I
SINK
= 1.2mA
(LM3723 -2.32/3.08)
0.3
V
V
CC
= V
TH
max, I
SINK
= 3.2mA
(LM3723 -4.63)
0.4
LM3722/LM3723/LM3724
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4
Electrical Characteristics
(Continued)
Typical values are at T
A
= +25C. Limits with standard typeface are for T
A
= +25C, and limits in boldface type apply for the
operating temperature range (-40C to +85C) for LM372_IM5X, and (-40C to +125C) for LM372_EM5X, unless otherwise
noted. (Note 4)
Symbol
Parameter
Conditions
Min
Typ
Max
Units
V
OH
RESET Output Voltage High
(LM3723)
1.8V
<
V
CC
<
V
TH
min, I
SOURCE
= 150A
0.8V
CC
V
V
OL
RESET Output Voltage Low
(LM3724)
V
CC
= V
TH
min, I
SINK
= 1.2 mA
(LM3724 -2.32/3.08)
0.3
V
V
CC
= V
TH
min, I
SINK
= 3.2 mA
(LM3724 -4.63)
0.4
V
CC
>
1V, I
SINK
= 50A
0.3
I
IN
RESET Output Leakage
Current (LM3724)
V
CC
>
V
TH
, RESET = 5.5V
0.5
A
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which the device operates
correctly. Operating ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical
Characteristics.
Note 2: The human body model is a 100pF capacitor discharged through a 1.5k
resistor into each pin.
Note 3: At elevated temperatures, devices must be derated based on package thermal resistance. The device in the SOT23-5 package must be derated at
4.5mW/C at ambient temperatures above 70C. The device has internal thermal protection.
Note 4: Production testing done at T
A
= +25C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control
(SQC) methods.
Note 5: RESET Output for LM3722 and LM3724, RESET output for LM3723.
Note 6: Glitches of 100 ns or less typically will not generate a reset pulse.
LM3722/LM3723/LM3724
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