LM431
LM431 Adjustable Precision Zener Shunt Regulator
Literature Number: SNVS020F
LM431
September 2, 2010
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. 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.
Features
■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
1005501
Top View
SO-8: 8-Pin Surface Mount
1005502
Top view
SOT-23: 3-Lead Small Outline
1005528
Top View
Note: NC = Not internally connected.
© 2010 National Semiconductor Corporation 10055 www.national.com
LM431 Adjustable Precision Zener Shunt Regulator
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
Symbol and Functional Diagrams
1005599
1005555
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LM431
DC Test Circuits
1005504
FIGURE 1. Test Circuit for VZ = VREF
1005505
Note: VZ = VREF (1 + R1/R2) + IREF• R1
FIGURE 2. Test Circuit for VZ > VREF
1005506
FIGURE 3. Test Circuit for Off-State Current
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LM431
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 −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 (Note 2,
Note 3)
TO-92 Package
SO-8 Package
SOT-23 Package
0.78W
0.81W
0.28W
Operating Conditions
Min Max
Cathode Voltage VREF 37V
Cathode Current 1.0 mA 100 mA
LM431 Electrical Characteristics
TA = 25°C unless otherwise specified
Symbol Parameter Conditions Min Typ Max Units
VREF Reference Voltage VZ = VREF, II = 10 mA 2.440 2.495 2.550 V
LM431A (Figure 1 )
VZ = VREF, II = 10 mA 2.470 2.495 2.520 V
LM431B (Figure 1 )
VZ = VREF, II = 10 mA 2.485 2.500 2.510 V
LM431C (Figure 1 )
VDEV Deviation of Reference Input Voltage Over VZ = VREF, II = 10 mA, 8.0 17 mV
Temperature (Note 4) TA = Full Range (Figure 1 )
Ratio of the Change in Reference Voltage IZ = 10 mA VZ from VREF to 10V −1.4 −2.7 mV/V
to the Change in Cathode Voltage (Figure 2 ) VZ from 10V to 36V −1.0 −2.0
IREF Reference Input Current R1 = 10 kΩ, R2 = ∞, 2.0 4.0 μA
II = 10 mA (Figure 2 )
∝IREF Deviation of Reference Input Current over R1 = 10 kΩ, R2 = ∞,
Temperature II = 10 mA, 0.4 1.2 μA
TA = Full Range (Figure 2 )
IZ(MIN) Minimum Cathode Current for Regulation VZ = VREF (Figure 1 ) 0.4 1.0 mA
IZ(OFF) Off-State Current VZ = 36V, VREF = 0V (Figure 3) 0.3 1.0 μA
rZDynamic Output Impedance (Note 5) VZ = VREF, LM431A, 0.75 Ω
Frequency = 0 Hz (Figure 1 )
VZ = VREF, LM431B, LM431C 0.50 Ω
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
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LM431
Typical Performance Characteristics
Input Current vs VZ
1005529
Thermal Information
1005530
Input Current vs VZ
1005531
Dynamic Impedance vs Frequency
1005509
Stability Boundary Conditions
1005511
Note: The areas under the curves represent conditions that may cause the de-
vice 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 de-
termine the ranges of stability.
1005510
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LM431
Test Circuit for Curve A Above
1005512
Test Circuit for Curves B, C and D Above
1005513
Typical Applications
Shunt Regulator
1005514
Single Supply Comparator with
Temperature Compensated Threshold
1005515
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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
Notes
LM431 Adjustable Precision Zener Shunt Regulator
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