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| HIGH TEMPERATURE ADJUSTABLE PRECISION ZENER SHUNT REGULATOR ISSUE 1 JULY 1997 DEVICE DESCRIPTION The ZHT2431 is a three terminal adjustable shunt regulator offering excellent temperature stability and output current handling capability up to 25mA. The output voltage may be set to any chosen voltage between 1.24 and 15 volts by selection of two external divider resistors. The devices can be used as a replacement for zener diodes in many applications requiring an improvement in zener performance. The ZHT2431 is particularly used in the feedback control loop of switch mode power supplies. In this application the device 1.24 volt reference enables the generation of low voltage supplies, typically 3.3 volts or 3 volts. The ZHT2431 is intended for use over the extended operating range of -55C to 125C. ZHT2431 FEATURES * * * * * * * * * * * * * * Surface mount SOT23 package TO92 package 2.5% tolerance Average temperature coefficient 50 ppm/C Temperature compensated for operation over the full temperature range Programmable output voltage 100A to 25mA current sink capability Low output noise -55 to 125 C operation APPLICATIONS Shunt regulator Series regulator Voltage monitor Over voltage/ under voltage protection Switch mode power supplies SCHEMATIC DIAGRAM VZ Vref Gnd ZHT2431 Cathode Voltage (VZ) 15V Cathode Current 50mA Operating Temperature -55 to 125C Storage Temperature -55 to 125C Recommended Operating Conditions Cathode Voltage (min)VREF to (max) 15V Cathode Current (min) 100A to (max) 25mA ABSOLUTE MAXIMUM RATING Power Dissipation (Tamb=25C, Tjmax=150C) SOT23 330mW TO92 780mW ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated):Tamb=25C PARAMETER Reference Voltage Deviation of Reference Input Voltage over Temperature VALUE SYMBOL MIN TYP MAX UNITS CONDITIONS 2.5% Vref Vdev 1.21 1.24 1.27 V 5.0 0.5 15.0 mV 2.0 IL=10mA (Fig1), VZ=Vref IL=10mA, VZ=Vref Ta=full range (Fig1) Ratio of the change in Vref Reference Voltage to the VZ Change in Cathode Voltage Reference Input Current Deviation of Reference Input Current over Temperature Minimum Cathode Current for Regulation Off-state Current Dynamic Output Impedance Iref Iref IZmin IZoff RZ mV/V VZ from Vref to 10V IZ=10mA (Fig2) A A A A R1=10K, R2=O/C, lL=10mA (Fig2) R1=10K, R2=O/C, IL=10mA Ta=full range (Fig2) VZ=15V, Vref =0V (Fig3) VZ=Vref (Fig1), f=0Hz, IL=10mA 0.02 0.11 0.4 0.02 0.2 30 10 100 30 0.25 2 Deviation of reference input voltage, Vdev, is defined as the maximum variation of the reference input voltage over the full temperature range. The average temperature coefficient of the reference input voltage, Vref is defined as: Vdev x 1000000 Vref (ppm C)= Vmax Vref (T1-T2) The dynamic output impedance, Rz, is defined VZ as: RZ = IZ When the device is programmed with two external resistors, R1 and R2, (fig 2) , the dynamic output impedance of the overall circuit, R, is defined as: R1 R =Rz 1+ Vmin Vdev = Vmax - Vmin R2 T1 Temperature T2 With a capacitance of greater than 100pF between cathode and anode, minimum cathode current must be 0.2mA. ZHT2431 TYPICAL CHARACTERISTICS 140 130 120 110 100 90 80 -50 -25 0 25 50 75 100 125 Vref = Vz Iz=10mA 2 1 0 -1 -2 -3 -4 -5 0 5 10 Iz = 10mA 15 Temperature (C) Cathode Voltage (V) Reference Current v Temperature 26 24 22 20 18 16 14 -50 -25 0 25 50 75 100 125 Change in Vref v Cathode Voltage 10 Vref = Vz 1mA Vref = Vz 10mA 1 0.1 100 1k 10k 100k Cathode Current v Temperature 1.244 1.242 1.240 1.238 1.236 Iz=10mA Temperature (C) Dynamic Impedance vs. Frequency 1.0 Frequency (Hz) 0.5 TO92 SOT23 1.234 1.232 -50 -25 0 25 50 75 100 125 0 25 50 75 100 125 Reference Voltage v Temperature Temperature (C) Power Dissipation Derating Ambient Temperature (C) TYPICAL CHARACTERISTICS 60 50 40 30 20 10 0 100 1k 10k 100k 1M Iz = 10mA ZHT2431 IZ VZ 240 47k 10F + 47k - Frequency (Hz) IZ = 10mA, TA = 25C Gain v Frequency 2.0 1.0 0 5.0 2.5 0 0 100 200 INPUT Single Pulse Vz Repetitive Pulse Test Circuit for Open Loop Voltage Gain Input Monitor 120 V Z Pulse Generator 50 300 400 500 TA = 25C Time (us) Pulse Response Test Circuit for Pulse Response Vref < VZ < 20, IZ = 10mA, TA = 25C 30 25 20 15 10 5 0 10p 100p 1n 10n .1 1 10 UNSTABLE STABLE STABLE Input 150 VZ IZ 10k 100F Stablity Boundary Conditions Load Capacitance(F) Test Circuit for Stability Boundary Conditions ZHT2431 APPLICATION CIRCUITS V+ R1 Vref R2 Vout V+ Vout R1 Vref R2 Vout = 1 + R1 R2 Vref Vout = 1 + R1 R2 Vref SHUNT REGULATOR HIGHER CURRENT SHUNT REGULATOR V+ V+ ZSR*** In Common Vout R1 Vref R2 Vref Vout MIN = Vref + Vreg R1 Vout = 1 + R2 R2 Vout 0.01F R1 Out 30 Vref Vout = 1 + OUTPUT CONTROL OF A THREE TERMINAL FIXED REGULATOR R1 R2 Vref SERIES REGULATOR V+ V+ INPUT OUTPUT V on 2V V off = V+ R1A Vref R2A R1B Vref OUTPUT V TH = 2.5V R2B Low limit = High limit = 1+ R1B R2B Vref Vref SINGLE SUPPLY COMPARATOR WITH TEMPERATURE COMPENSATED THRESHOLD R1A 1+ R2A OVER VOLTAGE / UNDER VOLTAGE PROTECTION CIRCUIT DC Test Circuits Input IL VZ Input ZHT2431 IL VZ Input VZ Iref IZ 1F R1 Iref IZ 1F I zoff 1F Vref R2 Vref Fig 1 Test Circuit for Vz=Vref Fig 2 Test Circuit for Vz>Vref Fig 3 Test Circuit for Off State current Voltage Regulator Connection Diagrams SOT23 Package Suffix F TO92 Package Suffix C Top View Bottom View Ordering Information Part Number ZHT2431F02 ZHT2431C02 Package SOT23 TO92 Part Mark 24F ZHT243102 |
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