LM809,LM810
LM809/LM810 3-Pin Microprocessor Reset Circuits
Literature Number: SNVS052C
LM809/LM810
3-Pin Microprocessor Reset Circuits
General Description
The LM809/810 microprocessor supervisory circuits can be
used to monitor the power supplies in microprocessor and
digital systems. They provide a reset to the microprocessor
during power-up, power-down and brown-out conditions.
The function of the LM809/810 is to monitor the V
CC
supply
voltage, and assert a reset signal whenever this voltage
declines below the factory-programmed reset threshold. The
reset signal remains asserted for 240ms after V
CC
rises
above the threshold. The LM809 has an active-low RESET
output, while the LM810 has an active-high RESET output.
Seven standard reset voltage options are available, suitable
for monitoring 5V, 3.3V, and 3V supply voltages.
With a low supply current of only 15µA, the LM809/810 are
ideal for use in portable equipment. The LM809/LM810 are
available in the 3-pin SOT23 package and in the 6-Lead LLP
package.
Features
nPrecise monitoring of 3V, 3.3V, and 5V supply voltages
nSuperior upgrade to MAX809/810
nFully specified over temperature
n140ms min. Power-On Reset pulse width, 240ms typical
Active-low RESET Output (LM809)
Active-high RESET Output (LM810)
nGuaranteed RESET Output valid for V
CC
≥1V
nLow Supply Current, 15µA typ.
nPower supply transient immunity
Applications
nMicroprocessor Systems
nComputers
nControllers
nIntelligent Instruments
nPortable/Battery-Powered Equipment
nAutomotive
Typical Application Circuit
10105701
Connection Diagrams
10105702
( ) are for LM810
10105715
Top View
See NS package Number LDB06A
( ) are for LM810
September 2002
LM809/LM810 3-Pin Microprocessor Reset Circuits
© 2002 National Semiconductor Corporation DS101057 www.national.com
Ordering Information
Reset Threshold
(V)
LM809 Supplied as 1000
units, tape & reel
LM809 Supplied as 3000
units, tape & reel
Package
Top Mark
Package
Type NSC Package
4.63 LM809M3-4.63 LM809M3X-4.63 S8B
SOT23-3 M03B
4.38 LM809M3-4.38 LM809M3X-4.38 S7B
4.00 LM809M3-4.00 LM809M3X-4.00 S6B
3.08 LM809M3-3.08 LM809M3X-3.08 S5B
2.93 LM809M3-2.93 LM809M3X-2.93 S4B
2.63 LM809M3-2.63 LM809M3X-2.63 S3B
2.45 LM809M3-2.45 LM809M3X-2.45 SFB
Reset Threshold
(V)
LM810 Supplied as 1000
units, tape & reel
LM810 Supplied as 3000
units, tape & reel
Package
Top Mark
Package
Type NSC Package
4.63 LM810M3-4.63 LM810M3X-4.63 SEB
SOT23-3 M03B
4.38 LM810M3-4.38 LM810M3X-4.38 SDB
4.00 LM810M3-4.00 LM810M3X-4.00 SCB
3.08 LM810M3-3.08 LM810M3X-3.08 SBB
2.93 LM810M3-2.93 LM810M3X-2.93 SAB
2.63 LM810M3-2.63 LM810M3X-2.63 S9B
Reset Threshold
(V)
LM809 Supplied as 1000
units, tape & reel
LM809 Supplied as 4500
units, tape & reel
Package
Top Mark
Package
Type NSC Package
2.63 LM809LD-2.63 LM809LDX-2.63 S13 LLP-6 LDB06A
Custom voltages and improved accuracies are available, subject to minimum orders. Contact your local National Semiconductor Sales Office for information.
Pin Descriptions
PIN NAME FUNCTION
(LLP) SOT-23
1 1 GND Ground reference
32
RESET (LM809) Active-low output. RESET remains low while V
CC
is below the reset threshold,
and for 240ms after V
CC
rises above the reset threshold.
RESET (LM810) Active-high output. RESET remains high while V
CC
is below the reset
threshold, and for 240ms after V
CC
rises above the reset threshold.
53 V
CC
Supply Voltage (+5V, +3.3V, or +3.0V)
LM809/LM810
www.national.com 2
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
−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
Rate of Rise, V
CC
100V/µs
ESD Rating (Note 2) 2kV
Continuous Power Dissipation
(Note 4) 320mW
θ
JA
:
LLP-6 152˚C/W
SOT23-3 326˚C/W
Ambient Temperature Range −40˚C to +105˚C
Maximum Junction Temperature 125˚C
Storage Temperature Range −65˚C to +160˚C
Lead Temperature (soldering,
10sec) +300˚C
Electrical Characteristics
V
CC
= full range, T
A
= −40˚C to +105˚C, unless otherwise noted. Typical values are at T
A
= +25˚C, V
CC
= 5V for
4.63/4.38/4.00 versions, V
CC
= 3.3V for 3.08/2.93 versions, and V
CC
= 3V for 2.63/2.45 version (Note 3).
Symbol Parameter Conditions Min Typ Max Units
V
CC
Range T
A
= 0˚C to +70˚C 1.0 5.5 V
T
A
= −40˚C to +105˚C 1.2 5.5
I
CC
Supply Current
T
A
= −40˚C to
+85˚C
V
CC
<5.5V, LM8_ _
-4.63/4.38/4.00
18 60
µA
V
CC
<3.6V, LM8_ _
-3.08/2.93/2.63/2.45
15 50
T
A
= +85˚C to
+105˚C
V
CC
<5.5V, LM8_ _
-4.63/4.38/4.00
100
V
CC
<3.6V, LM8_ _
-3.08/2.93/2.63/2.45
100
V
TH
Reset Threshold (Note 5)
LM8_ _ -4.63
T
A
= +25˚C 4.56 4.63 4.70
V
T
A
= −40˚C to +85˚C 4.50 4.75
T
A
= +85˚C to +105˚C 4.40 4.86
LM8_ _ -4.38
T
A
= +25˚C 4.31 4.38 4.45
T
A
= −40˚C to +85˚C 4.25 4.50
T
A
= +85˚C to +105˚C 4.16 4.56
LM8_ _ -4.00
T
A
= +25˚C 3.93 4.00 4.06
T
A
= −40˚C to +85˚C 3.89 4.10
T
A
= +85˚C to +105˚C 3.80 4.20
LM8_ _ -3.08
T
A
= +25˚C 3.04 3.08 3.11
T
A
= −40˚C to +85˚C 3.00 3.15
T
A
= +85˚C to +105˚C 2.92 3.23
LM8_ _ -2.93
T
A
= +25˚C 2.89 2.93 2.96
T
A
= −40˚C to +85˚C 2.85 3.00
T
A
= +85˚C to +105˚C 2.78 3.08
LM8_ _ -2.63
T
A
= +25˚C 2.59 2.63 2.66
T
A
= −40˚C to +85˚C 2.55 2.70
T
A
= +85˚C to +105˚C 2.50 2.76
LM8_ _ -2.45
T
A
= +25˚C 2.41 2.45 2.49
T
A
= −40˚C to +85˚C 2.38 2.52
T
A
= +85˚C to +105˚C 2.33 2.57
Reset Threshold
Temperature Coefficient 30 ppm/˚C
V
CC
to Reset Delay (Note 5) V
CC
=V
TH
to (V
TH
− 100mV) 20 µs
Reset Active Timeout Period T
A
= −40˚C to +85˚C 140 240 560 ms
T
A
= +85˚C to +105˚C 100 840
LM809/LM810
www.national.com3
Electrical Characteristics (Continued)
V
CC
= full range, T
A
= −40˚C to +105˚C, unless otherwise noted. Typical values are at T
A
= +25˚C, V
CC
= 5V for
4.63/4.38/4.00 versions, V
CC
= 3.3V for 3.08/2.93 versions, and V
CC
= 3V for 2.63/2.45 version (Note 3).
Symbol Parameter Conditions Min Typ Max Units
V
OL
RESET Output Voltage Low
(LM809)
V
CC
=V
TH
min, I
SINK
= 1.2mA,
LM809-2.45/2.63/2.93/3.08
0.3
VV
CC
=V
TH
min, I
SINK
= 3.2mA,
LM809-4.63/4.38/4.00
0.4
V
CC
>1.0V, I
SINK
= 50µA 0.3
V
OH
RESET Output Voltage High
(LM809)
V
CC
>V
TH
max, I
SOURCE
= 500µA,
LM809-2.45/2.63/2.93/3.08
0.8V
CC
V
V
CC
>V
TH
max, I
SOURCE
= 800µA,
LM809-4.63/4.38/4.00
V
CC
−1.5
V
OL
RESET Output Voltage Low
(LM810)
V
CC
=V
TH
max, I
SINK
= 1.2mA,
LM810-2.63/2.93/3.08
0.3
V
V
CC
=V
TH
max, I
SINK
= 3.2mA,
LM810-4.63/4.38/4.00
0.4
V
OH
RESET Output Voltage High
(LM810) 1.8V <V
CC
<V
TH
min, I
SOURCE
= 150µA 0.8V
CC
V
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 1.5kΩresistor into each pin.
Note 3: Production testing done at TA= +25˚C, over temperature limits guaranteed by design only.
Note 4: At elevated temperatures, devices must be derated based on package thermal resistance. The device in the SOT23-3 package must be derated at 4mW/˚C
at ambient temperatures above 70˚C. The device has internal thermal protection.
Note 5: RESET Output for LM809, RESET output for LM810.
LM809/LM810
www.national.com 4
Typical Performance Characteristics
Supply Current vs Temperature
(No Load, LM8_ _-2.63/2.93/3.08)
10105703
Supply Current vs Temperature
(No Load, LM8_ _-4.63/4.38)
10105704
Power-Down Reset Delay vs Temp
(LM8_ _-2.63/2.93/3.08)
10105705
Power-Down Reset Delay vs Temperature
(LM8_ _-4.63/4.38)
10105706
Power-Up Reset Timeout vs Temperature
10105707
Normalized Reset Threshold vs Temperature
10105708
LM809/LM810
www.national.com5
Applications Information
Benefits of Precision Reset Thresholds
A microprocessor supply supervisor must provide a reset
output within a predictable range of the supply voltage. A
common threshold range is between 5% and 10% below the
nominal supply voltage. The 4.63V and 3.08V options of the
LM809/810 use highly accurate circuitry to ensure that the
reset threshold occurs only within this range (for 5V and 3.3V
supplies). The other voltage options have the same tight
tolerance to ensure a reset signal for other narrow monitor
ranges. See Table 1 for examples of how the standard reset
thresholds apply to 3V, 3.3V, and 5V nominal supply volt-
ages.
TABLE 1. Reset Thresholds Related to Common
Supply Voltages
Reset
Threshold 3.0V 3.3V 5.0V
4.63 ±3% 90 - 95%
4.38 ±3% 85 - 90%
4.00 ±3% 78 - 82%
3.08 ±3% 90 - 95%
2.93 ±3% 86 - 90%
2.63 ±3% 85 - 90% 77 - 81%
2.45 ±3% 79 - 84% 72 - 76%
Ensuring a Valid Reset Output Down to V
CC
=0V
When V
CC
falls below 1V, the LM809 RESET output no
longer sinks current. A high-impedance CMOS logic input
connected to RESET can therefore drift to undetermined
voltages. To prevent this situation, a 100kΩresistor should
be connected from the RESET output to ground, as shown in
Figure 1.
A 100kΩpull-up resistor to V
CC
is also recommended for the
LM810, if RESET is required to remain valid for V
CC
<1V.
Negative-Going V
CC
Transients
The LM809/810 are relatively immune to short
negative-going transients or glitches on V
CC
.Figure 2 shows
the maximum pulse width a negative-going V
CC
transient
can have without causing a reset pulse. In general, as the
magnitude of the transient increases, going further below the
threshold, the maximum allowable pulse width decreases.
Typically, for the 4.63V and 4.38V version of the LM809/810,
aV
CC
transient that goes 100mV below the reset threshold
and lasts 20µs or less will not cause a reset pulse. A 0.1 µF
bypass capacitor mounted as close as possible to the V
CC
pin will provide additional transient rejection.
Interfacing to µPs with Bidirectional Reset Pins
Microprocessors with bidirectional reset pins, such as the
Motorola 68HC11 series, can be connected to the LM809
RESET output. To ensure a correct output on the LM809
even when the microprocessor reset pin is in the opposite
state, connect a 4.7kΩresistor between the LM809 RESET
output and the µP reset pin, as shown in Figure 3. Buffer the
LM809 RESET output to other system components.
LLP Mounting
The LLP package requires special mounting techniques
which are detailed in National Semiconductor Application
Note AN-1187. Referring to the section PCB Design Recom-
mendations, it should be noted that the pad style which
should be used with the LLP package is the NSMD (non-
solder mask defined) type.
10105710
FIGURE 1. RESET Valid to V
CC
= Ground Circuit
10105709
FIGURE 2. Maximum Transient Duration without
Causing a Reset Pulse vs. Reset Comparator
Overdrive
10105711
FIGURE 3. Interfacing to Microprocessors with
Bidirectional Reset I/O
LM809/LM810
www.national.com 6
Physical Dimensions inches (millimeters) unless otherwise noted
3-Lead SOT23-3
For Ordering, refer to Ordering Information table
NS Package Number M03B
6-Lead LLP (NLDBB006)
For Ordering, refer to Ordering Information table
NS Package Number LDB06A
LM809/LM810
www.national.com7
Notes
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www.national.com
LM809/LM810 3-Pin Microprocessor Reset Circuits
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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