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A Product Line of Diodes Incorporated
TLV431
1.24V COST EFFECTIVE SHUNT REGULATOR
Description
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. The TLV431 is available in 2 grades with initial tolerances of 1% and 0.5% for the A and B grades respectively.
Pin Assignments
TLV431_H6 (SC70-6)
CATHODE N/C
1 2 3
6 ANODE 5 4 NC
REF
NC
(Top View)
TLV431_F (SOT23)
Features
* * * Low Voltage Operation VREF = 1.24V Temperature range -40 to 125C Reference Voltage Tolerance at 25C o 0.5% TLV431B o 1% TLV431A Typical temperature drift o 4 mV (0C to 70C) o 6 mV (-40C to 85C) o 11mV (-40C to 125C) 80A Minimum cathode current 0.25 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
REF
1 3 ANODE
CATHODE
2
(Top View)
*
TLV431_E5 (SOT25)
N/C N/C
1 2 3
5
ANODE
* * * * *
CATHODE
4
REF
(Top View)
Typical Application Circuit
Secondary side regulated rail Primary side controller
3.3V
TLV431
Document number: DS32088 Rev. 4 - 2
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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) Human Body Model Machine Model Charged Device Model Rating 20 -20 to 20 -0.050 to 3 -0.03 to 18 4 400 1 Unit V mA mA V kV V kV
(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 -40 Max 18 15 125 Units V mA C
Package Thermal Data
Package SOT23 SOT25 SC70-6 JA 380C/W 250C/W 380C/W PDIS TA =25C, TJ = 150C 330 mW 500 mW 330 mW
TLV431
Document number: DS32088 Rev. 4 - 2
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TLV431 Electrical Characteristics
Electrical characteristics over recommended operating conditions, IKA = 10mA, TA = 25C, unless otherwise stated
Symbol
Parameter
VREF
Reference Voltage
VREF(dev) VREF VKA IREF IREF(dev)
Deviation of reference voltage over full temperature range Ration of change in refernce voltage to the change in cathode voltage Refernce Input Current IREF deviation over full temperature range Minimum cathode current for regulation Off state current Dynamic output impedance
Conditions TLV431A VKA = VREF, TA = 25C TLV431B TLV431A VKA = VREF, TA = 0 to 70C TLV431B TLV431A VKA = VREF, TA = -40 to 85C TLV431B TLV431A VKA = VREF, TA = -40 to 125C TLV431B TA = 0 to 70C VKA = VREF TA = -40 to 85C TA = -40 to 125C 6V VKA for VREF to 18V R1 = 10k, R2 = OC R1 = 10k, R2 = OC VKA = VREF VKA = 18V, VREF = 0V VKA = VREF, f = <1kHz IK = 0.1 to 15mA TA = 0 to 70C TA = -40 to 85C TA = -40 to 125C TA = 0 to 70C TA = -40 to 85C TA = -40 to 125C
Min. 1.228 1.234 1.221 1.227 1.215 1.224 1.209 1.221
Typ. 1.24 1.24
4 6 11 -1.5 -1.5 0.15 0.05 0.1 0.15 55 55 55 0.001 0.25
Max. 1.252 1.246 1.259 1.253 1.265 1.259 1.271 1.265 12 20 31 -2.7
Units
V
mV
mV/V -2.7 0.5 0.3 0.4 0.5 80 80 100 0.1 0.4 A A
IKMIN IK(OFF) ZKA
A A
TLV431
Document number: DS32088 Rev. 4 - 2
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TLV431 Typical Characteristics
56k S1
75k
IK
O/P
10mA
100nF 10k
Test circuit for VREF measurement
TLV431
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TLV431 Typical Characteristics (Cont.)
TLV431
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TLV431 Typical Characteristics (Cont.)
3V 1k 470F
750 O/P
Test circuit for input noise voltage
6.8k IK 10F 180
O/P
~
4.3k
5V
Test circuit for phase shift and gain
100F 100
100 O/P
~
50
Test circuit for reference impedance
TLV431
Document number: DS32088 Rev. 4 - 2
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TLV431 Typical Characteristics (Cont.) O/P Pulse Generator
Test circuit for pulse response
TLV431
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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 IK
R3 =
VIN - VKA IL + IK
where
R VKA = VREF x 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
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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 =
VBE IB
ISH hFE(min)
< 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
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TLV431 Application Information (Continued)
Printed circuit board layout considerations (continued)
R1 VOUT = VREF 1 + R2 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
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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% Orde Code TLV431AE5TA TLV431AFTA TLV431AH6TA TLV431BE5TA TLV431BFTA TLV431BH6TA Pack SOT25 SOT23 SC70-6 SOT25 SOT23 SC70-6 Part Mark V1A V1A V1A V1B V1B V1B Status Active Active Active Active Active Active Reel Size 7", 7", 7", 7", 7", 7", 180mm 180mm 180mm 180mm 180mm 180mm Tape Width 8mm 8mm 12mm 8mm 8mm 12mm Quanity per Reel 3000 3000 1000 3000 3000 1000
0.5%
TLV431
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TLV431 Package Outline Dimensions
SOT23 SOT25
Dimension Table SOT25
TLV431
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TLV431 Package Outline Dimensions (Continued)
SC70-6
TLV431
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TLV431
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TLV431
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