HIGH TEMPERATURE ADJUSTABLE PRECISION ZENER SHUNT REGULATOR ZHT2431 ISSUE 1 JULY 1997 DEVICE DESCRIPTION FEATURES 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 -55°C to 125°C. SCHEMATIC DIAGRAM • • • • 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 100µA 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 VZ Vref Gnd ZHT2431 ABSOLUTE MAXIMUM RATING Power Dissipation (Tamb=25°C, Tjmax=150°C) SOT23 330mW TO92 780mW Cathode Voltage (VZ) 15V Cathode Current 50mA Operating Temperature -55 to 125°C Storage Temperature -55 to 125°C Recommended Operating Conditions Cathode Voltage (min)VREF to (max) 15V Cathode Current (min) 100µA to (max) 25mA ELECTRICAL CHARACTERISTICS TEST CONDITIONS (Unless otherwise stated):Tamb=25°C VALUE SYMBOL MIN TYP MAX UNITS CONDITIONS PARAMETER Reference Voltage 2.5% Vref Deviation of Reference Input Voltage over Temperature 1.21 1.24 1.27 V Vdev Ratio of the change in ∆Vref Reference Voltage to the ∆VZ Change in Cathode Voltage 5.0 15.0 mV 0.5 2.0 IL=10mA (Fig1), VZ=Vref IL=10mA, VZ=Vref Ta=full range (Fig1) mV/V VZ from Vref to 10V IZ=10mA (Fig2) 0.02 0.11 0.4 µA R1=10K, R2=O/C, lL=10mA (Fig2) ∆Iref 0.02 0.2 µA R1=10K, R2=O/C, IL=10mA Ta=full range (Fig2) IZmin 30 100 µA Off-state Current IZoff 10 30 µA VZ=15V, Vref =0V (Fig3) Dynamic Output Impedance RZ 0.25 2 Ω VZ=Vref (Fig1), f=0Hz, IL=10mA Reference Input Current Iref Deviation of Reference Input Current over Temperature Minimum Cathode Current for Regulation 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 T1 Temperature T2 R2 With a capacitance of greater than 100pF between cathode and anode, minimum cathode current must be 0.2mA. ZHT2431 TYPICAL CHARACTERISTICS 140 2 Vref = Vz Iz=10mA 130 0 120 -1 110 -2 100 -3 90 80 Iz = 10mA 1 -4 -50 -25 0 25 50 -5 75 100 125 0 5 10 15 Temperature (°C) Cathode Voltage (V) Reference Current v Temperature Change in Vref v Cathode Voltage 26 10 Vref = Vz Vref = Vz 1mA Ω 24 22 10mA 20 1 18 16 14 -50 -25 0 25 50 75 100 125 Temperature (°C) Cathode Current v Temperature 0.1 100 1k 10k 100k Frequency (Hz) Dynamic Impedance vs. Frequency 1.0 1.244 1.242 Iz=10mA 1.240 1.238 0.5 1.236 TO92 SOT23 1.234 1.232 -50 -25 0 25 50 Temperature (°C) 75 100 125 Reference Voltage v Temperature 0 25 50 75 100 Ambient Temperature (°C) Power Dissipation Derating 125 ZHT2431 TYPICAL CHARACTERISTICS 60 Iz = 10mA 50 40 VZ IZ 47k 240Ω 10µF 30 + 20 47k - 10 0 100 1k 10k 100k 1M Frequency (Hz) IZ = 10mA, TA = 25°C Test Circuit for Open Loop Voltage Gain Gain v Frequency 120Ω Input Monitor Single Pulse 2.0 VZ Vz 1.0 Repetitive Pulse Pulse Generator 0 5.0 2.5 50Ω INPUT 0 0 100 200 300 400 500 Time (us) TA = 25°C Test Circuit for Pulse Response Pulse Response Vref < VZ < 20, IZ = 10mA, TA = 25°C 30 Input 25 STABLE 150Ω VZ IZ 20 10k 15 STABLE UNSTABLE 10 100µF 5 0 10p 100p 1n 10n .1µ 1µ 10µ Load Capacitance(F) Stablity Boundary Conditions Test Circuit for Stability Boundary Conditions ZHT2431 APPLICATION CIRCUITS V+ Vout V+ Vout R1 R1 Vref Vref R2 R2 Vout = 1 + R1 R2 Vref Vout = 1 + SHUNT REGULATOR R1 R2 Vref HIGHER CURRENT SHUNT REGULATOR V+ ZSR*** In V+ Vout Out Common 30 R1 0.01µF Vref R1 R2 Vref Vout MIN = Vref + Vreg R1 Vout = 1 + R2 Vref Vout = 1 + OUTPUT CONTROL OF A THREE TERMINAL FIXED REGULATOR R1 R2 Vref SERIES REGULATOR V+ V+ INPUT Vout R2 OUTPUT V on 2V V off = V+ V TH = 2.5V SINGLE SUPPLY COMPARATOR WITH TEMPERATURE COMPENSATED THRESHOLD R1A R1B Vref Vref R2A R2B Low limit = 1+ R1B R2B Vref High limit = R1A 1+ R2A Vref OVER VOLTAGE / UNDER VOLTAGE PROTECTION CIRCUIT OUTPUT ZHT2431 DC Test Circuits IL Input I ref VZ IL Input IZ R1 I ref VZ IZ 1µF Fig 1 Test Circuit for Vz=Vref VZ I zoff 1µF R2 Vref Input 1µF 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 Package Part Mark ZHT2431F02 SOT23 24F ZHT2431C02 TO92 ZHT243102