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. (c) 2010 National Semiconductor Corporation 10055 www.national.com 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 0C to +70C LM431CIZ/ LM431CIZ LM431BIZ/ LM431BIZ LM431AIZ/ LM431AIZ -40C to +85C 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 0C to +70C Tape & Reel M08A Rails -40C to +85C Tape &Reel Rails 0C to +70C Tape & Reel MF03A Rails -40C to +85C Tape &Reel Symbol and Functional Diagrams 1005599 1005555 www.national.com 2 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 3 www.national.com 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 -65C to +150C -40C to +85C 0C to +70C 235C 260C (lead temp.) 37V -10 mA to +150 mA -0.5V 10 mA 0.78W 0.81W 0.28W LM431 Electrical Characteristics TA = 25C 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 A 0.4 1.2 A 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 k, R2 = , VZ from 10V to 36V II = 10 mA (Figure 2 ) IREF Deviation of Reference Input Current over R1 = 10 k, 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 A 0.75 0.50 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 = 150C. Note 3: Ratings apply 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, 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. www.national.com 4 LM431 1005507 The average temperature coefficient of the reference input voltage, VREF, is defined as: Where: T2 - T1 = full temperature change (0-70C). 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 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 www.national.com 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. www.national.com 6 Test Circuit for Curves B, C and D Above 1005512 1005513 Typical Applications Shunt Regulator 1005514 Single Supply Comparator with Temperature Compensated Threshold 1005515 7 www.national.com 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 www.national.com 8 LM431 Crow Bar 1005519 Over Voltage/Under Voltage Protection Circuit 1005520 9 www.national.com LM431 Voltage Monitor 1005521 Delay Timer 1005522 Current Limiter or Current Source 1005523 www.national.com 10 LM431 Constant Current Sink 1005524 11 www.national.com 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 www.national.com 12 LM431 NS Package Number Z03A 13 www.national.com LM431 Adjustable Precision Zener Shunt Regulator Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH(R) Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise(R) Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagicTM www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise(R) Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION ("NATIONAL") PRODUCTS. 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