TL/H/10055
LM431 Adjustable Precision Zener Shunt Regulator
December 1996
LM431
Adjustable Precision Zener Shunt Regulator
General Description
The LM431 is a 3-terminal adjustable shunt regulator with
guaranteed temperature stability over the entire tempera-
ture range of operation. The output voltage may be set at
any level greater than 2.5V (VREF) 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 excellent replacement for many zener diode applica-
tions.
Features
YAverage temperature coefficient 50 ppm/§C
YTemperature compensated for operation over the full
temperature range
YProgrammable output voltage
YFast turn-on response
YLow output noise
Connection Diagrams
TO-92: Plastic Package
TL/H/100551
Top View
Order Number LM431ACZ,
LM431AIZ,
LM431BCZ, LM431BIZ, LM431CCZ
or LM431CIZ
SO-8: 8-Pin Surface Mount
TL/H/100552
Top View
Order Number LM431ACM,
LM431AIM,
LM431BCM, LM431BIM, LM431CCM
or LM431CIM
SOT-23: 3-Lead Small Outline
TL/H/1005528
Top View
Order Number LM431ACM3,
LM431AIM3,
LM431BCM3, LM431BIM3,
LM431CCM3
or LM431CIM3
Ordering Information*
Package Typical Accuracy Temperature Range
0.5% 1% 2%
TO-92 LM431CCZ LM431BCZ LM431ACZ 0§Ctoa
70§C
LM431CIZ LM431BIZ LM431AIZ b40§Ctoa
85§C
SO-8 LM431CCM LM431BCM LM431ACM 0§Ctoa
70§C
LM431CIM LM431BIM LM431AIM b40§Ctoa
85§C
SOT-23 LM431CCM3 LM431BCM3 LM431ACM3 0§Ctoa
70§C
LM431CIM3 LM431BIM3 LM431AIM3 b40§Ctoa
85§C
*See Table 1 for package marking for SOT-23.
C1996 National Semiconductor Corporation RRD-B30M17/Printed in U. S. A. http://www.national.com
Absolute Maximum Ratings
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales
Office/Distributors for availability and specifications.
Storage Temperature Range b65§Ctoa
150§C
Operating Temperature Range
Industrial (LM431xI) b40§Ctoa
85§C
Commercial (LM431xC) 0§Ctoa
70§C
Lead Temperature
TO-92 Package/SO-8 Package/SOT-23 Package
(Soldering, 10 sec.) 265§C
Internal Power Dissipation (Notes 1, 2)
TO-92 Package 0.78W
SO-8 Package 0.81W
SOT-23 Package 0.28W
Cathode Voltage 37V
Continuous Cathode Current b10 mA to a150 mA
Reference Voltage b0.5V
Reference Input Current 10 mA
Operating Conditions Min Max
Cathode Voltage VREF 37V
Cathode Current 1.0 mA 100 mA
Note 1: TJ Max e150§C.
Note 2: Ratings appy to ambient temperature at 25§C. Above this tempera-
ture, derate the TO-92 at 6.2 mW/§C, the SO-8 at 6.5 mW/§C, and the
SOT-23 at 2.2 mW/§C.
LM431
Electrical Characteristics TAe25§C unless otherwise specified
Symbol Parameter Conditions Min Typ Max Units
VREF Reference Voltage VZeVREF,I
Ie10 mA 2.440 2.495 2.550 V
LM431A
(Figure 1)
VZeVREF,I
Ie10 mA 2.470 2.495 2.520 V
LM431B
(Figure 1)
VZeVREF,I
Ie10 mA 2.485 2.500 2.510 V
LM431C
(Figure 1)
VDEV Deviation of Reference Input VZeVREF,I
Ie10 mA, 8.0 17 mV
Voltage Over Temperature (Note 3) TAeFull Range
(Figure 1)
DVREF
DVZ
Ratio of the Change in Reference IZe10 mA VZfrom VREF to 10V b1.4 b2.7 mV/V
Voltage to the Change in Cathode
(Figure 2)
VZfrom 10V to 36V b1.0 b2.0
Voltage
IREF Reference Input Current R1e10 kX,R
2e%
,2.0 4.0 mA
IIe10 mA
(Figure 2)
*IREF Deviation of Reference Input Current R1e10 kX,R
2e%
,
over Temperature IIe10 mA, 0.4 1.2 mA
TAeFull Range
(Figure 2)
IZ(MIN) Minimum Cathode Current for VZeVREF
(Figure 1)
0.4 1.0 mA
Regulation
IZ(OFF) Off-State Current VZe36V, VREF e0V
(Figure 3)
0.3 1.0 mA
rZDynamic Output Impedance (Note 4) VZeVREF, LM431A, 0.75 X
Frequency e0Hz
(Figure 1)
VZeVREF, LM431B, LM431C 0.50 X
Frequency e0Hz
(Figure 1)
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LM431
Electrical Characteristics TAe25§C unless otherwise specified (Continued)
Note 3: Deviation of reference input voltage, VDEV, is defined as the maximum variation of the reference input voltage over the full temperature range.
TL/H/100557
The average temperature coefficient of the reference input voltage, *VREF, is defined as:
*VREF
ppm
§Ce
gÐVMax bVMin
VREF (at 25§C) (106
T2bT1
e
gÐVDEV
VREF (at 25§C) (106
T2bT1
Where:
T2bT1efull temperature change.
*VREF can be positive or negative depending on whether the slope is positive or negative.
Example: VDEV e8.0 mV, VREF e2495 mV, T2bT1e70§C, slope is positive.
*VREF eÐ8.0 mV
2495 mV (106
70§Cea
46 ppm/§C
Note 4: The dynamic output impedance, rZ, is defined as:
rZeDVZ
DIZ
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:
rZeDVZ
DIZ
jÐrZ#1aR1
R2 J(
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Equivalent Circuit
TL/H/100553
DC Test Circuits
TL/H/100554
FIGURE 1. Test Circuit for VZeVREF
TL/H/100555
Note: VZeVREF (1 aR1/R2) aIREF #R1
FIGURE 2. Test Circuit for VZlVREF
TL/H/100556
FIGURE 3. Test Circuit for Off-State Current
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Typical Performance Characteristics
Input Current vs VZThermal Information Input Current vs VZ
TL/H/100558
Dynamic Impedance vs
Frequency
TL/H/100559
TL/H/1005510
Stability Boundary Conditions
TL/H/1005511
Note 1: The areas under the curves represent conditions that may cause the
device to oscillate. For curves B, C, and D, R2 and Vawere adjusted to
establish the initial VZand IZconditions with CLe0. Vaand CLwere then
adjusted to determine the ranges of stability.
Test Circuit for Curve A Above
TL/H/1005512
Test Circuit for Curves B, C and D Above
TL/H/1005513
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Typical Applications
Shunt Regulator
TL/H/1005514
VO&#1aR1
R2 JVREF
Series Regulator
TL/H/1005516
VO&#1aR1
R2 JVREF
Single Supply Comparator with
Temperature Compensated Threshold
TL/H/1005515
Output Control of a Three
Terminal Fixed Regulator
TL/H/1005517
VOe#1aR1
R2 JVREF
VO MIN eVREF a5V
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Typical Applications (Continued)
Higher Current Shunt Regulator
TL/H/1005518
VOe#1aR1
R2 JVREF
Crow Bar
TL/H/1005519
VLIMIT &#1aR1
R2 JVREF
Over Voltage/Under Voltage
Protection Circuit
TL/H/1005520
LOW LIMIT &VREF #1aR1B
R2B JaVBE
HIGH LIMIT &VREF #1aR1A
R2A J
Voltage Monitor
TL/H/1005521
LED ON WHEN
LOW LIMIT &VREF #1aR1B
R2B JLOW LIMIT kVakHIGH LIMIT
HIGH LIMIT &VREF #1aR1A
R2A J
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Typical Applications (Continued)
Delay Timer
TL/H/1005522
DELAY eR#C#
n
Va
(Va)bVREF
Current Limiter or Current Source
TL/H/1005523
IOeVREF
RCL
Constant Current Sink
TL/H/1005524
Recommended Solder Pads for SOT-23 Package
TL/H/1005527
TABLE 1. Package Marking for SOT-23
Order Number Top Mark
LM431ACM3 N1F
LM431AIM3 N1E
LM431BCM3 N1D
LM431BIM3 N1C
LM431CCM3 N1B
LM431CIM3 N1A
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Physical Dimensions inches (millimeters) unless otherwise noted
Order Number LM431ACM or LM431AIM
NS Package Number M08A
SOT-23 Molded Small Outline Transistor Package (M3)
Order Number LM60BIM3 or LM60CIM3
NS Package Number MA03B
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LM431 Adjustable Precision Zener Shunt Regulator
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number LM431ACZ or LM431AIZ
NS Package Number Z03A
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