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LM431
Adjustable Precision Zener Shunt Regulator
General Description
Features
The LM431 is a 3-terminal adjustable shunt regulator with
guaranteed temperature stability over the entire temperature
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 applications.
■ Average temperature coefficient 50 ppm/°C
■ Temperature compensated for operation over the full
temperature range
■ Programmable output voltage
■ Fast turn-on response
■ Low output noise
Connection Diagrams
TO-92: Plastic Package
SOT-23: 3-Lead Small Outline
1005528
1005501
Top View
Top View
SO-8: 8-Pin Surface Mount
1005502
Top view
Note: NC = Not internally connected.
© 2010 National Semiconductor Corporation
10055
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LM431 Adjustable Precision Zener Shunt Regulator
September 2, 2010
LM431
Ordering Information
Package
TO-92
SO-8
SOT-23
Typical Accuracy Order Number/Package Marking
Temperature
Range
0.5%
1%
2%
LM431CCZ/
LM431CCZ
LM431BCZ/
LM431BCZ
LM431ACZ/
LM431ACZ
0°C to +70°C
LM431CIZ/
LM431CIZ
LM431BIZ/
LM431BIZ
LM431AIZ/
LM431AIZ
−40°C to +85°C
LM431CCM/
431CCM
LM431BCM/
431BCM
LM431ACM/
LM431ACM
LM431CCMX/
431CCM
LM431BCMX/
431BCM
LM431ACMX/
LM431ACM
LM431CIM/
431CIM
LM431BIM/
431BIM
LM431AIM/
LM431AIM
LM431CIMX/
431CIM
LM431BIMX/
431BIM
LM431AIMX/
LM431AIM
LM431CCM3/
N1B
LM431BCM3/
N1D
LM431ACM3/
N1F
LM431CCM3X/
N1B
LM431BCM3X/
N1D
LM431ACM3X/
N1F
LM431CIM3
N1A
LM431BIM3
N1C
LM431AIM3
N1E
LM431CIM3X
N1A
LM431BIM3X
N1C
LM431AIM3X
N1E
Transport
Media
NSC
Drawing
Rails
Z03A
Rails
0°C to +70°C
Tape & Reel
M08A
Rails
−40°C to +85°C
Tape &Reel
Rails
0°C to +70°C
Tape & Reel
MF03A
Rails
−40°C to +85°C
Tape &Reel
Symbol and Functional Diagrams
1005599
1005555
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LM431
DC Test Circuits
1005504
1005505
Note:
VZ = VREF (1 + R1/R2) + IREF• R1
FIGURE 1. Test Circuit for VZ = VREF
FIGURE 2. Test Circuit for VZ > VREF
1005506
FIGURE 3. Test Circuit for Off-State Current
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LM431
Operating Conditions
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Storage Temperature Range
Operating Temperature Range
Industrial (LM431xI)
Commercial (LM431xC)
Soldering Information
Infrared or Convection (20 sec.)
Wave Soldering (10 sec.)
Cathode Voltage
Continuous Cathode Current
Reference Voltage
Reference Input Current
Internal Power Dissipation (Note 2,
Note 3)
TO-92 Package
SO-8 Package
SOT-23 Package
Min
VREF
1.0 mA
Cathode Voltage
Cathode Current
Max
37V
100 mA
−65°C to +150°C
−40°C to +85°C
0°C to +70°C
235°C
260°C (lead temp.)
37V
−10 mA to +150 mA
−0.5V
10 mA
0.78W
0.81W
0.28W
LM431 Electrical Characteristics
TA = 25°C unless otherwise specified
Symbol
VREF
Parameter
Reference Voltage
Conditions
VZ = VREF, II = 10 mA
Min
Typ
Max
Units
2.440
2.495
2.550
V
2.470
2.495
2.520
V
2.485
2.500
2.510
V
8.0
17
mV
−1.4
−2.7
mV/V
−1.0
−2.0
2.0
4.0
μA
0.4
1.2
μA
1.0
mA
LM431A (Figure 1 )
VZ = VREF, II = 10 mA
LM431B (Figure 1 )
VZ = VREF, II = 10 mA
LM431C (Figure 1 )
VDEV
Deviation of Reference Input Voltage Over
VZ = VREF, II = 10 mA,
Temperature (Note 4)
TA = Full Range (Figure 1 )
Ratio of the Change in Reference Voltage
IREF
IZ = 10 mA
VZ from VREF to 10V
to the Change in Cathode Voltage
(Figure 2 )
Reference Input Current
R1 = 10 kΩ, R2 = ∞,
VZ from 10V to 36V
II = 10 mA (Figure 2 )
∝IREF
Deviation of Reference Input Current over
R1 = 10 kΩ, R2 = ∞,
Temperature
II = 10 mA,
TA = Full Range (Figure 2 )
IZ(MIN)
Minimum Cathode Current for Regulation
VZ = VREF (Figure 1 )
0.4
IZ(OFF)
Off-State Current
VZ = 36V, VREF = 0V (Figure 3)
0.3
rZ
Dynamic Output Impedance (Note 5)
VZ = VREF, LM431A,
1.0
μA
0.75
Ω
0.50
Ω
Frequency = 0 Hz (Figure 1 )
VZ = VREF, LM431B, LM431C
Frequency = 0 Hz (Figure 1 )
Note 1: 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 2: TJ Max = 150°C.
Note 3: 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.
Note 4: Deviation of reference input voltage, VDEV, is defined as the maximum variation of the reference input voltage over the full temperature range.
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LM431
1005507
The average temperature coefficient of the reference input voltage, ∝VREF, is defined as:
Where:
T2 − T1 = 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 − T1 = 70°C, slope is positive.
Note 5: 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
1005503
5
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LM431
Typical Performance Characteristics
Input Current vs VZ
Thermal Information
1005529
1005530
Input Current vs VZ
Dynamic Impedance vs Frequency
1005531
1005509
Stability Boundary Conditions
1005510
1005511
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 VZ and IZ conditions with CL = 0. V+ and CL were then adjusted to determine the ranges of stability.
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Test Circuit for Curves B, C and D Above
1005512
1005513
Typical Applications
Shunt Regulator
1005514
Single Supply Comparator with
Temperature Compensated Threshold
1005515
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LM431
Test Circuit for Curve A Above
LM431
Series Regulator
1005516
Output Control of a Three
Terminal Fixed Regulator
1005517
Higher Current Shunt Regulator
1005518
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LM431
Crow Bar
1005519
Over Voltage/Under Voltage
Protection Circuit
1005520
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LM431
Voltage Monitor
1005521
Delay Timer
1005522
Current Limiter or Current Source
1005523
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LM431
Constant Current Sink
1005524
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LM431
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
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LM431
NS Package Number Z03A
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LM431 Adjustable Precision Zener Shunt Regulator
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