A Product Line of Diodes Incorporated TLV431 1.24V COST EFFECTIVE SHUNT REGULATOR Description Pin Assignments TLV431_H6 (SC70-6) The TLV431 is a three terminal adjustable shunt regulator offering excellent temperature stability and output current handling capability up to 20mA. The output voltage may be set to any chosen voltage between 1.24 and 18 volts by selection of two external divider resistors. The TLV431 can be used as a replacement for zener diodes in many applications requiring an improvement in zener performance. CATHODE 1 6 ANODE N/C ‡ 2 5 NC REF 3 4 NC ‡ (Top View) The TLV431 is available in 2 grades with initial tolerances of 1% and 0.5% for the A and B grades respectively. TLV431_F (SOT23) REF Features 1 3 • • • • • • • • • Low Voltage Operation VREF = 1.24V Temperature range -40 to 125ºC Reference Voltage Tolerance at 25°C o 0.5% TLV431B o 1% TLV431A Typical temperature drift o 4 mV (0°C to 70°C) o 6 mV (-40°C to 85°C) o 11mV (-40°C to 125°C) 80µA Minimum cathode current 0.25Ω Typical Output Impedance Adjustable Output Voltage VREF to 18V Lead Free Finish. RoHS Compliant with “Green” Molding Compound (No Br, Sb) Qualified to AEC-Q100 CATHODE ANODE 2 (Top View) TLV431_E5 (SOT25) N/C 1 ‡ 2 CATHODE 3 N/C 5 ANODE 4 REF (Top View) Typical Application Circuit Secondary side regulated rail 3.3V Primary side controller TLV431 Document number: DS32088 Rev. 4 - 2 1 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Absolute Maximum Ratings (Voltages to GND Unless Otherwise Stated) Symbol VKA IKA IREF VIN ESD Susceptibility HBM MM CDM Parameter Cathode Voltage Continuous Cathode Current Reference Input Current Range Input Supply Voltage (Relative to Ground) Rating 20 -20 to 20 -0.050 to 3 -0.03 to 18 Unit V mA mA V 4 400 1 kV V kV Human Body Model Machine Model Charged Device Model (Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events. Suitable ESD precautions should be taken when handling and transporting these devices.) Parameter Operating Junction Temperature Storage Temperature Rating -40 to 150 -65 to 150 Unit °C °C Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability. Unless otherwise stated voltages specified are relative to the ANODE pin. These are stress ratings only. Operation outside the absolute maximum ratings may cause device failure. Recommended Operating Conditions VKA Cathode Voltage IKA Cathode Current TA Operating Ambient Temperature Range Min VREF 0.1 Max 18 15 Units V mA -40 125 °C Package Thermal Data Package θJA SOT23 SOT25 SC70-6 380°C/W 250°C/W 380°C/W PDIS TA =25°C, TJ = 150°C 330 mW 500 mW 330 mW TLV431 Document number: DS32088 Rev. 4 - 2 2 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Electrical Characteristics Electrical characteristics over recommended operating conditions, IKA = 10mA, TA = 25°C, unless otherwise stated Symbol VREF VREF(dev) ΔVREF ΔVKA IREF Parameter Reference Voltage Deviation of reference voltage over full temperature range Ration of change in refernce voltage to the change in cathode voltage Refernce Input Current Conditions TLV431A VKA = VREF, TA = 25°C TLV431B TLV431A VKA = VREF, TA = 0 to 70°C TLV431B TLV431A VKA = VREF, TA = -40 to 85°C TLV431B TLV431A VKA = VREF, TA = -40 to 125°C TLV431B TA = 0 to 70°C VKA = VREF TA = -40 to 85°C TA = -40 to 125°C -1.5 -2.7 18V -1.5 -2.7 0.15 0.5 0.05 0.1 0.15 55 55 55 0.001 0.3 0.4 0.5 80 80 100 0.1 0.25 0.4 TA = 0 to 70°C TA = -40 to 85°C TA = -40 to 125°C TA = 0 to 70°C TA = -40 to 85°C TA = -40 to 125°C IKMIN Minimum cathode current for regulation VKA = VREF Off state current Dynamic output impedance VKA = 18V, VREF = 0V VKA = VREF, f = <1kHz IK = 0.1 to 15mA Document number: DS32088 Rev. 4 - 2 6V R1 = 10kΩ, R2 = OC R1 = 10kΩ, R2 = OC TLV431 4 6 11 Max. 1.252 1.246 1.259 1.253 1.265 1.259 1.271 1.265 12 20 31 Units V mV mV/V IREF deviation over full temperature range ZKA Typ. 1.24 1.24 VKA for VREF to IREF(dev) IK(OFF) Min. 1.228 1.234 1.221 1.227 1.215 1.224 1.209 1.221 3 of 14 www.diodes.com µA µA µA µA Ω November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Typical Characteristics 56kΩ 75kΩ IK O/P S1 10mA 100nF 10kΩ Test circuit for VREF measurement TLV431 Document number: DS32088 Rev. 4 - 2 4 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Typical Characteristics (Cont.) TLV431 Document number: DS32088 Rev. 4 - 2 5 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Typical Characteristics (Cont.) 3V 1kΩ 470µF 750Ω O/P Test circuit for input noise voltage O/P 6.8kΩ IK 10µF 180Ω 5V ~ 4.3kΩ Test circuit for phase shift and gain 100Ω 100µF 100Ω ~ O/P 50Ω Test circuit for reference impedance TLV431 Document number: DS32088 Rev. 4 - 2 6 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Typical Characteristics (Cont.) O/P Pulse Generator Test circuit for pulse response TLV431 Document number: DS32088 Rev. 4 - 2 7 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Application Information In a conventional shunt regulator application (Figure 1), an external series resistor (R3) is connected between the supply voltage, VIN, and the TLV431. R3 determines the current that flows through the load (IL) and the TLV431 (IK). The TLV431 will adjust how much current it sinks or “shunts” to maintain a voltage equal to VREF across its feedback pin. Since load current and supply voltage may vary, R3 should be small enough to supply at least the minimum acceptable IKMIN to the TLV431 even when the supply voltage is at its minimum and the load current is at its maximum value. When the supply voltage is at its maximum and IL is at its minimum, R3 should be large enough so that the current flowing through the TLV431 is less than 15 mA. R3 is determined by the supply voltage, (VIN), the load and operating current, (IL and IK), and the TLV431’s reverse breakdown voltage, VKA. IL R3 = IK VIN − VKA IL + IK where ⎛ R ⎞ VKA = VREF × ⎜⎜ 1 + 1 ⎟⎟ R 2⎠ ⎝ and VKA = VOUT Figure 1 The values of R1 and R2 should be large enough so that the current flowing through them is much smaller than the current through R3 yet not too large that the voltage drop across them caused IREF affects the reference accuracy. The most frequent application of the TLV431 is in isolated low output voltage power supplies where the regulated output is galvanically isolated from the controller. As shown in figure 2 the TLV431 drives current, IF, through the opto-coupler’s LED which in turn drives the isolated transistor which is connected to the controller on the primary side of the power supply. This completes the feedback path through the isolation barrier and ensures that a stable isolated supply is maintained. Assuming a forward drop of 1.4V across the opto-coupler diode allows output voltages as low as 2.7V to be regulated. R1 ⎞ ⎛ VOUT = VREF ⎜⎜1 + ⎟ R2 ⎟⎠ ⎝ VOUT(max) − 2.7 VOUT − 2.7 > R3 ≥ IF(min) 15mA Figure 2. Using the TLV431 as the regulating element in an isolated PSU TLV431 Document number: DS32088 Rev. 4 - 2 8 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Application Information (Continued) Printed circuit board layout considerations The TLV431 in the SOT25 package has the die attached to pin 2, which results in an electrical contact between pin 2 and pin 5. Therefore, pin 2 of the SOT25 package must be left floating or connected to pin 5. TLV431 in the SC70-6 package has the die attached to pin 2 and 5, which results in an electrical contact between pins 2, 5 and pin 6. Therefore, pins 2 and 5 must be left floating or connected to pin 6. Other applications of the TLV431 R1 ⎞ ⎛ VOUT = VREF ⎜ 1 + ⎟ ⎝ R2 ⎠ R3 = VIN − VOUT ISH + IB R4 = ⎛ ISH ⎜ ⎜ hFE(min) ⎝ VBE IB ⎞ ⎟ < IB ≤ 15mA ⎟ ⎠ Figure 3. High current shunt regulator It may at times be required to shunt-regulate more current than the 15mA that the TLV431 is capable of. Figure 3 shows how this can be done using transistor Q1 to amplify the TLV431’s current. Care needs to be taken that the power dissipation and/or SOA requirements of the transistor is not exceeded. R1 ⎞ ⎛ VOUT = VREF ⎜ 1 + ⎟ R2 ⎠ ⎝ R3 = VIN − ( VOUT + VBE ) IB ⎛ IOUT(max) ⎞ ⎜ ⎟ < I ≤ 15mA ⎜ hFE(min) ⎟ B ⎝ ⎠ Figure 4. Basic series regulator A very effective and simple series regulator can be implemented as shown in Figure 4 above. This may be preferable if the load requires more current than can be provided by the TLV431 alone and there is a need to conserve power when the load is not being powered. This circuit also uses one component less than the shunt circuit shown in Figure 3 above. TLV431 Document number: DS32088 Rev. 4 - 2 9 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Application Information (Continued) Printed circuit board layout considerations (continued) R1 ⎞ ⎛ VOUT = VREF ⎜1 + ⎟ R 2⎠ ⎝ V − ( VOUT + VBE ) R3 = IN IB ⎛ IOUT(max) ⎞ ⎜ ⎟ < I ≤ 18mA ⎜ hFE(min) ⎟ B ⎝ ⎠ RS = VREF IOUT(max) Figure 5. Series regulator with current limit Figure 5 adds current limit to the series regulator in Figure 4 using a second TLV431. For currents below the limit, the circuit works normally supplying the required load current at the design voltage. However should attempts be made to exceed the design current set by the second TLV431, the device begins to shunt current away from the base of Q1. This begins to reduce the output voltage and thus ensuring that the output current is clamped at the design value. Subject only to Q1’s ability to withstand the resulting power dissipation, the circuit can withstand either a brief or indefinite short circuit. R1 ⎞ ⎛ VOUT = VREF ⎜1 + ⎟ ⎝ R2 ⎠ VOUT ≥ ( VREG + VREF ) (All features of the regulator such as short circuit protection, thermal shutdown, etc, are maintained.) Figure 6. Increasing output voltage of a fixed linear regulator One of the useful applications of the TLV431 is in using it to improve the accuracy and/or extend the range and flexibility of fixed voltage regulators. In the circuit in Figure 6 above both the output voltage and its accuracy are entirely determined by the TLV431, R1 and R2. However the rest of the features of the regulator (up to 5A output current, output current limiting and thermal shutdown) are all still available. TLV431 Document number: DS32088 Rev. 4 - 2 10 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Application Information (Continued) Printed circuit board layout considerations (continued) R1 ⎞ ⎛ VOUT = VREF ⎜1 + ⎟ R2 ⎠ ⎝ VOUT ≥ ( VREG + VREF ) R3 = VIN − ( VOUT − VREG ) IB 0.1mA ≤ IB ≤ 18mA (All features of the regulator such as short circuit protection, thermal shutdown, etc, are maintained.) Figure 7. Adjustable linear voltage regulator Figure 7 is similar to Figure 6 with adjustability added. Note the addition of R3. This is only required for the AP1117 due to the fact that its ground or adjustment pin can only supply a few micro-Amps of current at best. R3 is therefore needed to provide sufficient bias current for the TLV431. Ordering Information Tol. 1% 0.5% Orde Code Pack Part Mark Status TLV431AE5TA TLV431AFTA TLV431AH6TA TLV431BE5TA TLV431BFTA TLV431BH6TA SOT25 SOT23 SC70-6 SOT25 SOT23 SC70-6 V1A V1A V1A V1B V1B V1B Active Active Active Active Active Active TLV431 Document number: DS32088 Rev. 4 - 2 Reel Size 7”, 7”, 7”, 7”, 7”, 7”, 11 of 14 www.diodes.com 180mm 180mm 180mm 180mm 180mm 180mm Tape Width 8mm 8mm 12mm 8mm 8mm 12mm Quanity per Reel 3000 3000 1000 3000 3000 1000 November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Package Outline Dimensions SOT23 SOT25 Dimension Table SOT25 TLV431 Document number: DS32088 Rev. 4 - 2 12 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 Package Outline Dimensions (Continued) SC70-6 TLV431 Document number: DS32088 Rev. 4 - 2 13 of 14 www.diodes.com November 2010 © Diodes Incorporated A Product Line of Diodes Incorporated TLV431 IMPORTANT NOTICE DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). 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