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
TO-92: Plastic Package
01005501
Top View
SO-8: 8-Pin Surface Mount
01005502
Top view
SOT-23: 3-Lead Small Outline
01005528
Top View
4-Bump micro SMD
01005554
Top View
(bump side down)
Note: *NC = Not internally connected. Must be electrically isolated from the rest of the circuit for the microSMD package.
March 2005
LM431 Adjustable Precision Zener Shunt Regulator
© 2005 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
M08A
LM431CCMX/
431CCM
LM431BCMX/
431BCM
LM431ACMX/
LM431ACM Tape & Reel
LM431CIM/
431CIM
LM431BIM/
431BIM
LM431AIM/
LM431AIM −40˚C to +85˚C
Rails
LM431CIMX/
431CIM
LM431BIMX/
431BIM
LM431AIMX/
LM431AIM Tape &Reel
SOT-23 LM431CCM3/
N1B
LM431BCM3/
N1D
LM431ACM3/
N1F 0˚C to +70˚C
Rails
MF03A
LM431CCM3X/
N1B
LM431BCM3X/
N1D
LM431ACM3X/
N1F Tape & Reel
LM431CIM3
N1A
LM431BIM3
N1C
LM431AIM3
N1E −40˚C to +85˚C
Rails
LM431CIM3X
N1A
LM431BIM3X
N1C
LM431AIM3X
N1E Tape &Reel
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
01005556
LM431
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Symbol and Functional Diagrams
01005599
01005555
DC Test Circuits
01005506
Test Circuit for Off-State Current
01005504
FIGURE 1. Test Circuit for V
Z
=V
REF
01005505
Note: VZ=V
REF (1 + R1/R2) + IREFR1
FIGURE 2. Test Circuit for V
Z
>V
REF
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
=10k,R
2
=, 2.0 4.0 µA
I
I
=10mA(Figure 2 )
I
REF
Deviation of Reference Input Current over R
1
=10k,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 *NO
TARGET FOR fi* )
0.3 1.0 µA
r
Z
Dynamic Output Impedance (Note 6) V
Z
=V
REF
, LM431A, 0.75
Frequency=0Hz(Figure 1 )
V
Z
=V
REF
, LM431B, LM431C 0.50
Frequency=0Hz(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)
01005507
The average temperature coefficient of the reference input voltage, VREF, is defined as:
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:
LM431
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Equivalent Circuit
01005503
Typical Performance Characteristics
Input Current vs V
Z
Thermal Information
01005529
01005530
Input Current vs V
Z
Dynamic Impedance vs Frequency
01005531 01005509
LM431
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Typical Performance Characteristics (Continued)
Stability Boundary Conditions
01005511
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.
01005510
Test Circuit for Curve A Above Test Circuit for Curves B, C and D Above
01005512 01005513
Typical Applications
Shunt Regulator
01005514
Single Supply Comparator with
Temperature Compensated Threshold
01005515
LM431
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Typical Applications (Continued)
Series Regulator
01005516
Output Control of a Three
Terminal Fixed Regulator
01005517
Higher Current Shunt Regulator
01005518
Crow Bar
01005519
LM431
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Typical Applications (Continued)
Over Voltage/Under Voltage
Protection Circuit
01005520
Voltage Monitor
01005521
LM431
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Typical Applications (Continued)
Delay Timer
01005522
Current Limiter or Current Source
01005523
Constant Current Sink
01005524
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.
LM431
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Physical Dimensions inches (millimeters) unless otherwise noted
8-Pin SOIC
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)
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
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.
For the most current product information visit us at www.national.com.
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LM431 Adjustable Precision Zener Shunt Regulator