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
n
Average temperature coefficient 50 ppm/C
n
Temperature compensated for operation over the full
temperature range
n
Programmable output voltage
n
Fast turn-on response
n
Low output noise
n
LM431 in micro SMD package
n
See 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
0C to +70C
Rails
Z03A
LM431CIZ/
LM431CIZ
LM431BIZ/
LM431BIZ
LM431AIZ/
LM431AIZ
-40C to +85C
SO-8
LM431CCM/
431CCM
LM431BCM/
431BCM
LM431ACM/
LM431ACM
0C to +70C
Rails and Tape &Reel
M08A
LM431CIM/
431CIM
LM431BIM/
431BIM
LM431AIM/
LM431AIM
-40C to +85C
SOT-23
LM431CCM3/
N1B
LM431BCM3/
N1D
LM431ACM3/
N1F
0C to +70C
Rails and Tape &Reel
MF03A
LM431CIM3
N1A
LM431BIM3
N1C
LM431AIM3
N1E
-40C to +85C
micro SMD
LM431AIBP
LM431AIBPX(Note 1)
-40C to +85C
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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2
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:
V
Z
= V
REF
(1 + R1/R2) + I
REF
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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3
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
-65C to +150C
Operating Temperature Range
Industrial (LM431xI)
-40C to +85C
Commercial (LM431xC)
0C to +70C
Soldering Information
Infrared or Convection (20 sec.)
235C
Wave Soldering (10 sec.)
260C (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
= 25C 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
= 10 mA
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
= 10 k
, R
2
=
,
2.0
4.0
A
I
I
= 10 mA
(Figure 2 )
I
REF
Deviation of Reference Input Current over
R
1
= 10 k
, R
2
=
,
Temperature
I
I
= 10 mA,
0.4
1.2
A
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
A
r
Z
Dynamic Output Impedance (Note 6)
V
Z
= V
REF
, LM431A,
0.75
Frequency = 0 Hz
(Figure 1 )
V
Z
= V
REF
, LM431B, LM431C
0.50
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: T
J Max
= 150C.
Note 4: Ratings apply to ambient temperature at 25C. 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, V
DEV
, is defined as the maximum variation of the reference input voltage over the full temperature range.
LM431
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4
LM431
Electrical Characteristics
(Continued)
Where:
T
2
- T
1
= full temperature change (0-70C).
V
REF
can be positive or negative depending on whether the slope is positive or negative.
Example: V
DEV
= 8.0 mV, V
REF
= 2495 mV, T
2
- T
1
= 70C, slope is positive.
Note 6: The dynamic output impedance, r
Z
, 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, r
Z
, is defined as:
Equivalent Circuit
DS010055-7
The average temperature coefficient of the reference input voltage,
V
REF
, 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 V
Z
and I
Z
conditions with C
L
= 0. V
+
and C
L
were 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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9
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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10
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
NS Package Number Z03A
LM431
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11
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
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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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Email: 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.
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