LM431
Adjustable Precision Zener Shunt Regulator
General Description
The LM431 is a 3-terminal adjustable shunt regulator with
guaranteed temperature stability over the entire temperature
range of operation. It is now available in a chip sized pack-
age (4-Bump micro SMD) using National’s micro SMD pack-
age technology. The output voltage may be set at any level
greater than 2.5V (V
REF
) up to 36V merely by selecting two
external resistors that act as a voltage divided network. Due
to the sharp turn-on characteristics this device is an excel-
lent replacement for many zener diode applications.
Features
nAverage temperature coefficient 50 ppm/˚C
nTemperature compensated for operation over the full
temperature range
nProgrammable output voltage
nFast turn-on response
nLow output noise
nLM431 in micro SMD package
nSee AN-1112 for micro SMD considerations
Connection Diagrams
Note: *NC = Not internally connected. Must be electrically isolated from the
rest of the circuit for the microSMD package.
TO-92: Plastic Package
DS010055-1
Top View
SO-8: 8-Pin Surface Mount
DS010055-2
Top view
SOT-23: 3-Lead Small Outline
DS010055-28
Top View
4-Bump micro SMD
DS010055-54
Top View
(bump side down)
March 2002
LM431 Adjustable Precision Zener Shunt Regulator
© 2002 National Semiconductor Corporation DS010055 www.national.com
Ordering Information
Package Typical Accuracy Order Number/Package Marking Temperature
Range Transport Media NSC
Drawing
0.5% 1% 2%
TO-92 LM431CCZ/
LM431CCZ LM431BCZ/
LM431BCZ LM431ACZ/
LM431ACZ 0˚C to +70˚C Rails Z03A
LM431CIZ/
LM431CIZ LM431BIZ/
LM431BIZ LM431AIZ/
LM431AIZ −40˚C to +85˚C
SO-8 LM431CCM/
431CCM LM431BCM/
431BCM LM431ACM/
LM431ACM 0˚C to +70˚C Rails and Tape &Reel M08A
LM431CIM/
431CIM LM431BIM/
431BIM LM431AIM/
LM431AIM −40˚C to +85˚C
SOT-23 LM431CCM3/
N1B LM431BCM3/
N1D LM431ACM3/
N1F 0˚C to +70˚C Rails and Tape &Reel MF03A
LM431CIM3
N1A LM431BIM3
N1C LM431AIM3
N1E −40˚C to +85˚C
micro SMD ––
LM431AIBP
LM431AIBPX(Note 1) −40˚C to +85˚C 250 Units Tape and Reel
3k Units Tape and Reel BPA04AFB
Note 1: The micro SMD package marking is a 1 digit manufacturing Date Code only
micro SMD Top View Marking Example
DS010055-56
LM431
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Symbol and Functional Diagrams
DC Test Circuits
DS010055-99
DS010055-55
DS010055-4
FIGURE 1. Test Circuit for V
Z
=V
REF
DS010055-5
Note: VZ=V
REF (1 + R1/R2) + IREF•R1
FIGURE 2. Test Circuit for V
Z
>V
REF
DS010055-6
FIGURE 3. Test Circuit for Off-State Current
LM431
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Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Storage Temperature Range −65˚C to +150˚C
Operating Temperature Range
Industrial (LM431xI) −40˚C to +85˚C
Commercial (LM431xC) 0˚C to +70˚C
Soldering Information
Infrared or Convection (20 sec.) 235˚C
Wave Soldering (10 sec.) 260˚C (lead temp.)
Cathode Voltage 37V
Continuous Cathode Current −10 mA to +150 mA
Reference Voltage −0.5V
Reference Input Current 10 mA
Internal Power Dissipation (Notes 3, 4)
TO-92 Package
SO-8 Package
SOT-23 Package
0.78W
0.81W
0.28W
micro SMD Package 0.30W
Operating Conditions
Min Max
Cathode Voltage V
REF
37V
Cathode Current 1.0 mA 100 mA
LM431
Electrical Characteristics
T
A
= 25˚C unless otherwise specified
Symbol Parameter Conditions Min Typ Max Units
V
REF
Reference Voltage V
Z
=V
REF
,I
I
= 10 mA 2.440 2.495 2.550 V
LM431A
(Figure 1 )
V
Z
=V
REF
,I
I
= 10 mA 2.470 2.495 2.520 V
LM431B
(Figure 1 )
V
Z
=V
REF
,I
I
= 10 mA 2.485 2.500 2.510 V
LM431C
(Figure 1 )
V
DEV
Deviation of Reference Input Voltage Over V
Z
=V
REF
,I
I
= 10 mA, 8.0 17 mV
Temperature (Note 5) T
A
= Full Range
(Figure 1 )
Ratio of the Change in Reference Voltage I
Z
=10mA V
Z
from V
REF
to 10V −1.4 −2.7 mV/V
to the Change in Cathode Voltage
(Figure 2 )
V
Z
from 10V to 36V −1.0 −2.0
I
REF
Reference Input Current R
1
=10kΩ,R
2
=∞
, 2.0 4.0 µA
I
I
=10mA
(Figure 2 )
∝I
REF
Deviation of Reference Input Current over R
1
=10kΩ,R
2
=∞
,
Temperature I
I
= 10 mA, 0.4 1.2 µA
T
A
= Full Range
(Figure 2 )
I
Z(MIN)
Minimum Cathode Current for Regulation V
Z
=V
REF
(Figure 1 )
0.4 1.0 mA
I
Z(OFF)
Off-State Current V
Z
= 36V, V
REF
=0V
(Figure 3 )
0.3 1.0 µA
r
Z
Dynamic Output Impedance (Note 6) V
Z
=V
REF
, LM431A, 0.75 Ω
Frequency = 0 Hz
(Figure 1 )
V
Z
=V
REF
, LM431B, LM431C 0.50 Ω
Frequency = 0 Hz
(Figure 1 )
Note 2: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
beyond its rated operating conditions.
Note 3: TJ Max = 150˚C.
Note 4: Ratings apply to ambient temperature at 25˚C. Above this temperature, derate the TO-92 at 6.2 mW/˚C, the SO-8 at 6.5 mW/˚C, the SOT-23 at 2.2 mW/˚C
and the micro SMD at 3mW/˚C.
Note 5: Deviation of reference input voltage, VDEV, is defined as the maximum variation of the reference input voltage over the full temperature range.
LM431
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LM431
Electrical Characteristics (Continued)
Where:
T2−T
1= full temperature change (0-70˚C).
∝VREF can be positive or negative depending on whether the slope is positive or negative.
Example: VDEV = 8.0 mV, VREF = 2495 mV, T2−T
1= 70˚C, slope is positive.
Note 6: The dynamic output impedance, rZ, is defined as:
When the device is programmed with two external resistors, R1 and R2, (see
Figure 2
), the dynamic output impedance of the overall circuit, rZ, is defined as:
Equivalent Circuit
DS010055-7
The average temperature coefficient of the reference input voltage, ∝VREF, is defined as:
DS010055-3
LM431
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Typical Performance Characteristics
Input Current vs V
Z
DS010055-29
Thermal Information
DS010055-30
Input Current vs V
Z
DS010055-31
Dynamic Impedance vs Frequency
DS010055-9
DS010055-10
Stability Boundary Conditions
DS010055-11
Note: The areas under the curves represent conditions that may cause the device to oscillate. For curves B, C, and D, R2 and V+were adjusted to establish
the initial VZand IZconditions with CL=0.V
+and CLwere then adjusted to determine the ranges of stability.
Test Circuit for Curve A Above
DS010055-12
Test Circuit for Curves B, C and D Above
DS010055-13
LM431
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Typical Applications
Shunt Regulator
DS010055-14
Single Supply Comparator with
Temperature Compensated Threshold
DS010055-15
Series Regulator
DS010055-16
Output Control of a Three
Terminal Fixed Regulator
DS010055-17
Higher Current Shunt Regulator
DS010055-18
Crow Bar
DS010055-19
LM431
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Typical Applications (Continued)
Over Voltage/Under Voltage
Protection Circuit
DS010055-20
Voltage Monitor
DS010055-21
LM431
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Typical Applications (Continued)
Application Info
1.0 Mounting
To ensure that the geometry of the micro SMD package
maintains good physical contact with the printed circuit
board, pin A1 (NC) must be soldered to the pcb. Please see
AN-1112 for more detailed information regarding board
mounting techniques for the micro SMD package.
2.0 LM431 micro SMD Light Sensitivity
When the LM431 micro SMD package is exposed to bright
sunlight, normal office fluorescent light, and other LED’s and
lasers, it operates within the guaranteed limits specified in
the electrical characteristics table.
Delay Timer
DS010055-22
Current Limiter or Current Source
DS010055-23
Constant Current Sink
DS010055-24
LM431
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Physical Dimensions inches (millimeters) unless otherwise noted
NS Package Number M08A
SOT-23 Molded Small Outline Transistor Package (M3)
NS Package Number MF03A
LM431
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
NS Package Number Z03A
LM431
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
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Corporation
Americas
Email: support@nsc.com
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Europe Fax: +49 (0) 180-530 85 86
Email: europe.support@nsc.com
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www.national.com
NOTES: UNLESS OTHERWISE SPECIFIED
1. EPOXY COATING
2. 63Sn/37Pb EUTECTIC BUMP
3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD.
4. PIN A1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION. REMAINING PINS ARE
NUMBERED.
5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS
PACKAGE LENGTH AND X3 IS PACKAGE HEIGHT.
6. REFERENCE JEDEC REGISTRATION MO-211, VARIATION BA.
4-Bump micro SMD
X1 = 0.777 X2 = 0.904 X3 = 0.850
NS Package Number BPA04AFB
LM431 Adjustable Precision Zener Shunt Regulator
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.
