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LM431 Adjustable Precision Zener Shunt Regulator
April 1998
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. 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
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
Connection Diagrams
TO-92: Plastic Package SO-8: 8-Pin Surface Mount
DS010055-2 DS010055-1
Top View Order Number LM431ACZ, LM431AIZ, LM431BCZ, LM431BIZ, LM431CCZ or LM431CIZ
Top View Order Number LM431ACM, LM431AIM, LM431BCM, LM431BIM, LM431CCM or LM431CIM
SOT-23: 3-Lead Small Outline
DS010055-28
Top View Order Number LM431ACM3, LM431AIM3, LM431BCM3, LM431BIM3, LM431CCM3 or LM431CIM3
Ordering Information (Note 1)
Package 0.5% TO-92 SO-8 SOT-23 LM431CCZ LM431CIZ LM431CCM LM431CIM LM431CCM3 LM431CIM3
Note 1: See Table 1 for package marking for SOT-23.
Typical Accuracy 1% LM431BCZ LM431BIZ LM431BCM LM431BIM LM431BCM3 LM431BIM3 2% LM431ACZ LM431AIZ LM431ACM LM431AIM LM431ACM3 LM431AIM3
Temperature Range 0C to +70C -40C to +85C 0C to +70C -40C to +85C 0C to +70C -40C to +85C
(c) 1998 National Semiconductor Corporation
DS010055
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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 -65C to +150C Operating Temperature Range Industrial (LM431xI) -40C to +85C Commercial (LM431xC) 0C to +70C Lead Temperature TO-92 Package/SO-8 Package/SOT-23 Package (Soldering, 10 sec.) 265C Internal Power Dissipation (Notes 3, 4) TO-92 Package 0.78W SO-8 Package 0.81W SOT-23 Package 0.28W
Cathode Voltage Continuous Cathode Current Reference Voltage Reference Input Current
37V -10 mA to +150 mA -0.5V 10 mA
Operating Conditions
Cathode Voltage Cathode Current Min VREF 1.0 mA Max 37V 100 mA
LM431 Electrical Characteristics
TA = 25C unless otherwise specified Symbol VREF Parameter Reference Voltage Conditions VZ = VREF, II = 10 mA LM431A (Figure 1 ) VZ = VREF, II = 10 mA LM431B (Figure 1 ) VZ = VREF, II = 10 mA VDEV Deviation of Reference Input Voltage Over Temperature (Note 5) Ratio of the Change in Reference Voltage to the Change in Cathode Voltage IREF IREF Reference Input Current Deviation of Reference Input Current over Temperature IZ(MIN) IZ(OFF) rZ Minimum Cathode Current for Regulation Off-State Current Dynamic Output Impedance (Note 6) LM431C (Figure 1 ) VZ = VREF, II = 10 mA, TA = Full Range (Figure 1 ) IZ = 10 mA VZ from VREF to 10V Min 2.440 2.470 2.485 Typ 2.495 2.495 2.500 8.0 -1.4 -1.0 2.0 Max 2.550 2.520 2.510 17 -2.7 -2.0 4.0 A Units V V V mV mV/V
(Figure 2 )
VZ from 10V to 36V
R1 = 10 k, R2 = , II = 10 mA (Figure 2 ) R1 = 10 k, R2 = , II = 10 mA, TA = Full Range (Figure 2 ) VZ = VREF (Figure 1 ) VZ = 36V, VREF = 0V (Figure 3 ) VZ = VREF, LM431A, Frequency = 0 Hz (Figure 1 ) VZ = VREF, LM431B, LM431C Frequency = 0 Hz (Figure 1 )
0.4 0.4 0.3
1.2 1.0 1.0 0.75 0.50
A mA A
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 = 150C. Note 4: Ratings appy 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, and the SOT-23 at 2.2 mW/ C.
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LM431 Electrical Characteristics
(Continued)
Note 5: Deviation of reference input voltage, VDEV, is defined as the maximum variation of the reference input voltage over the full temperature range.
DS010055-7
The average temperature coefficient of the reference input voltage, VREF, is defined as:
Where: T2 - T1 = full temperature change. 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 = 70C, 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:
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Equivalent Circuit
DS010055-3
DC Test Circuits
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FIGURE 1. Test Circuit for VZ = VREF
Note:
VZ = VREF (1 + R1/R2) + IREF * R1
FIGURE 2. Test Circuit for VZ > VREF
DS010055-6
FIGURE 3. Test Circuit for Off-State Current
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Typical Performance Characteristics
Input Current vs VZ Thermal Information Input Current vs VZ
DS010055-29
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Dynamic Impedance vs Frequency
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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 VZ and IZ conditions with CL = 0. V+ and CL were then adjusted to determine the ranges of stability.
Test Circuit for Curve A Above
Test Circuit for Curves B, C and D Above
DS010055-12
DS010055-13
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Typical Applications
Shunt Regulator Single Supply Comparator with Temperature Compensated Threshold
DS010055-14
DS010055-15
Series Regulator
Output Control of a Three Terminal Fixed Regulator
DS010055-16 DS010055-17
Higher Current Shunt Regulator
Crow Bar
DS010055-18
DS010055-19
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Typical Applications
(Continued) Over Voltage/Under Voltage Protection Circuit
DS010055-20
Voltage Monitor
DS010055-21
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Typical Applications
(Continued) Current Limiter or Current Source
Delay Timer
DS010055-23
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Constant Current Sink
DS010055-24
Recommended Solder Pads for SOT-23 Package
DS010055-27
TABLE 1. Package Marking for SOT-23 Order Number LM431ACM3 LM431AIM3 LM431BCM3 LM431BIM3 LM431CCM3 LM431CIM3 Top Mark N1F N1E N1D N1C N1B N1A
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Physical Dimensions
inches (millimeters) unless otherwise noted
Order Number LM431ACM, LM431AIM, LM431BCM, LM431BIM, LM431CCM, or LM431CIM NS Package Number M08A
SOT-23 Molded Small Outline Transistor Package (M3) Order Number LM431ACM3, LM431AIM3, LM431BCM3, LM431BIM3, LM431CCM3, or LM431CIM3 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, LM431AIZ, LM431BCZ, LM431BIZ, LM431CCZ, or LM431CIZ NS Package Number Z03A
LIFE SUPPORT POLICY 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 OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 2. A critical component in any component of a life support 1. Life support devices or systems are devices or sysdevice or system whose failure to perform can be reatems which, (a) are intended for surgical implant into sonably expected to cause the failure of the life support the body, or (b) support or sustain life, and whose faildevice or system, or to affect its safety or effectiveness. ure 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.
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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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