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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. TLV431_F (SOT23)
REF 1 3 ANODE CATHODE 2
TLV431_H6 (SC70-6)
CATHODE 1 N/C 2 REF 3 6 5 4 ANODE NC NC
Features
* * * Low Voltage Operation ........... VREF = 1.24V Temperature range -40 to 125C Reference Voltage Tolerance at 25C * 0.5%............TLV431B * 1%...............TLV431A Typical temperature drift * 4 mV (0C to 70C) * 6 mV (-40C to 85C) * 11mV (-40C to 125C) 80A Minimum cathode current 0.25 Typical Output Impedance Adjustable Output Voltage ..... VREF to 18V Opto-coupler linearisation Linear regulators Improved Zener Variable reference
TLV431_E5 (SOT23-5)
N/C
1
5
ANODE
N/C 2 CATHODE 3 4 REF
*
Connected internally to substrate; should be left floating or connected to anode
* * *
Applications
* * * *
Order Information
TOL Order code TLV431AE5TA TLV431AFTA TLV431AH6TA TLV431BE5TA TLV431BFTA TLV431BH6TA Pack SOT23-5 SOT23 SC70-6 SOT23-5 SOT23 SC70-6 Part mark V1A V1A V1A V1B V1B V1B 1 Status Active Active Active Active Active Active Reel Size (inches) 7 7 7 7 7 7 Tape width (mm) 8 8 8 8 8 8 Quantity per reel 3000 3000 3000 3000 3000 3000
1%
0.5%
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TLV431
Absolute Maximum Ratings
Cathode Voltage (VKA) ........................................................................... 20V Continuous Cathode Current (IKA) ........................................... -20 to 20mA Reference input current range (IREF).............................. -0.050 mA to 3mA Operating Junction Temperature............................................. -40 to 150C Storage Temperature ............................................................... -55 to 150C 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.
Package Thermal Data
Package SOT23 SOT23-5 SC70-6 JA 380C/W 250C/W 380oC/W PDIS TA =25C, TJ = 150C 330 mW 500 mW 330mW
Recommended Operating Conditions
Min VKA IKA TA Cathode Voltage Cathode Current Operating Ambient temperature range VREF 0.1 -40 Max 18 15 125 Units V mA C
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TLV431
Electrical Characteristics
Electrical characteristics over recommended operating conditions, IKA = 10mA, TA = 25C, unless otherwise stated.
Symbol Parameter Conditions VKA = VREF TA = 25C VKA = VREF TA = 0 to 70C VREF Reference voltage VKA = VREF TA = -40 to 85C VKA = VREF TA = -40 to 125C Deviation of reference voltage over full temperature range Ratio of change in reference voltage to the change in cathode voltage Reference Input Current IREF deviation over full temperature range TLV431A TLV431B TLV431A TLV431B TA = 0 to 70C VKA = VREF TA = -40 to 85C TA = -40 to 125C 6V VKA from VREF to 18V R1 = 10k R2 = OC TA = 0 to 70C R1 = 10k, R2 = OC TA = -40 to 85C TA = -40 to 125C TA = 0 to 70C VKA = VREF TA = -40 to 85C TA = -40 to 125C VKA = 18V VREF =0V VKA = VREF f = <1kHz IK = 0.1 to 15mA -1.5 0.15 0.05 0.1 0.15 55 55 55 0.001 0.25 -2.7 0.5 0.3 0.4 0.5 80 80 100 0.1 0.4 A A A A 1.215 1.224 1.209 1.221 4 6 11 -1.5 1.265 1.259 1.271 1.265 12 20 31 -2.7 mV/V mV TLV431A TLV431B TLV431A TLV431B Min 1.228 1.234 1.221 1.227 Typ 1.24 1.24 Max 1.252 1.246 1.259 1.253 V Units
VREF(dev)
VREF VKA
IREF
IREF(dev)
IKMIN
Minimum Cathode current for regulation Off state current Dynamic Output Impedance
IK(OFF) ZKA
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TLV431
Typical Characteristics
56k 75k I K S1 10mA 10k
O/P
100nF
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TLV431
Typical Characteristics
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TLV431
Typical Characteristics
3V 1k 470F 750 O/P
10F
6.8k IK
O/P 180 5V
~
4.3k
100F
R2 O/P
~
R1 50
IK R1 R2 0.1mA 1-15mA 1k 1k 100 100
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TLV431
Typical Characteristics
Pulse generator f = 100kHz
R 50
O/P
CL
S1 S2
10k I K
O/P
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TLV431
Application information
In a conventional shunt regulator application (Figure 1), an external series resistor (RS) is connected between the supply voltage 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.
R3 VIN IK
IL
R1 VREF
VOUT
R3 =
VS - VKA IL + IK
where
TLV431 C1 0.1F R2
R VKA = VREF x 1 + 1 R 2
and VKA = VOUT
GND
Figure 1. Basic shunt regulator 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.
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TLV431
Regulated supply Optocoupler To controller To controller IF
Regulated supply V OUT
R1 VOUT = VREF 1 + R2
R3
R1
TLV431
R2
VOUT(max) - 2.7 VOUT - 2.7 > R3 IF(min) 15mA
GND
Figure 2. Using the TLV431 as the regulating element in an isolated PSU
Printed circuit board layout considerations
The TLV431 in the SOT23-5 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 SOT23-5 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 TLV431
R3
VIN VOUT
R4
IB
TLV431
ZXTP2039F Q1
R1
R1 VOUT = VREF 1 + R2
V
C1 0.1F
REF
R3 =
VIN - (VOUT + VBE ) IB
< IB 15mA
R2
ISH
ISH hFE(min)
GND
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
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TLV431
ZXTN25020CFH VIN
I
OUT
VOUT
R3
IB
VREF
Q1
R1 VOUT = VREF 1 + R2
R1
R3 = VIN - ( VOUT + VBE ) IB +IK
I
TLV431
K
C1 0.1F
R2
IOUT(max) hFE(min)
< IB 15mA
GND
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 2 above.
R1 VOUT = VREF 1 + R2
R3 =
R1
VIN R3
ZXTN25020CFH IB Q1
Rs
IOUT
VOUT
VREF
VIN - ( VOUT + VBE ) IB +IK
TLV431 V REF TLV431 C1 0.1F
I OUT (max) < I B 15mA h FE (min)
R2
RS =
GND
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.
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TLV431
AP1084 VIN VIN GND Volt Reg VREG VREF VOUT R1 VOUT
R1 VOUT = VREF 1 + R2
VOUT (VREG + VREF )
TLV431
C1 0.1F R2
(All features of the regulator such as short circuit protection, thermal shutdown, etc, are maintained.)
GND
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.
AP1117
VIN IB R3
Vin
VR1 Vout
GND
VOUT
R1 VOUT = VREF 1 + R2
VOUT (VREG + VREF )
1.2V R1 VREF
R3 =
VIN - (VOUT - VREG ) IB
TLV431
C1 0.1F R2
0.1mA I B 15mA
(All features of the regulator such as short circuit protection, thermal shutdown, etc, are maintained.)
GND
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.
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V
R3 V+ ISH R1 VIN R2 VREF Flag
V+
Flag VIN
TLV431
VTH
GND
1.24 0
t
0.1mA I SH 18mA
R1 VTH = VREF 1 + R2
R3 =
V + - 1.24 I SH
Figure 8. Using the TLV431 as a level detector In its open loop state, the TLV431 is analogous to a line-powered comparator with its noninverting input internally connected to a 1.24V reference voltage. This means the remaining inverting input can be used for comparator functions. Figure 8 above shows the TLV431 being used as a level comparator. Its output (Flag) is normally high and goes low when the input reaches or exceeds the threshold (VTH) determined by R1 and R2.
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TLV431
Package Outline - SOT23
E
SOT23-5
e b 3 leads e1
L1
E1
D
A A1 L c
Dimension Table SOT23
Dim. Millimeters Min. A A1 b c D e 0.01 0.30 0.085 2.80 Max. 1.12 0.10 0.50 0.20 3.04 Min. 0.0004 0.012 0.003 0.110 Inches Max. 0.044 0.004 0.020 0.008 0.120 e1 E E1 L L1 Dim. Millimeters Min. Max. Min. Inches Max.
1.90 NOM 2.10 1.20 0.25 0.45 2.64 1.40 0.60 0.62 -
0.075 NOM 0.083 0.047 0.0098 0.018 0.104 0.055 0.0236 0.024 -
0.95 NOM
0.037 NOM
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
Dimension table - SOT23-5
Dim. Millimeters Min. A A1 A2 b C D 0.9 0.00 0.90 0.20 0.09 2.70 Max. 1.45 0.15 1.3 0.50 0.26 3.10 Min. 0.0354 0.00 0.0354 0.0078 0.0035 0.1062 Inches Max. 0.0570 0.0059 0.0511 0.0196 0.0102 0.1220 E E1 e e1 L ao Dim. Millimeters Min. 2.20 1.30 Max. 3.20 1.80 Min. 0.0866 0.0511 Inches Max. 0.1181 0.0708
0.95 REF 1.90 REF 0.10 0 0.60 30
0.0374 0.0748 0.0039 0 0.0236 30
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
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TLV431
Package outline - SC70-6
Dim.
Millimeters Min. Max. 1.10 0.10 1.00 0.30 0.25 Min.
Inches Max. 0.0433 0.0039 0.0394 0.0118 0.0098
Dim.
Millimeters Min. Max. Min.
Inches Max.
A A1 A2 b C D
0.80 0 0.80 0.15 0.08
0.0315 0 0.0315 0.006 0.0031
E E1 e e1 L ao
2.10 BSC 1.25 BSC 0.65 BSC 1.30 BSC 0.26 0 0.46 8
0.0826 BSC 0.0492 BSC 0.0255 BSC 0.0511 BSC 0.0102 0 0.0181 8
2.00 BSC
0.0787 BSC
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
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TLV431
Intentionally left blank
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TLV431
Definitions Product change Zetex Semiconductors reserves the right to alter, without notice, specifications, design, price or conditions of supply of any product or service. Customers are solely responsible for obtaining the latest relevant information before placing orders. Applications disclaimer The circuits in this design/application note are offered as design ideas. It is the responsibility of the user to ensure that the circuit is fit for the user's application and meets with the user's requirements. No representation or warranty is given and no liability whatsoever is assumed by Zetex with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. Zetex does not assume any legal responsibility or will not be held legally liable (whether in contract, tort (including negligence), breach of statutory duty, restriction or otherwise) for any damages, loss of profit, business, contract, opportunity or consequential loss in the use of these circuit applications, under any circumstances. Life support Zetex products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Zetex Semiconductors plc. As used herein: A. Life support devices or systems are devices or systems which: 1. are intended to implant into the body or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labelling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Reproduction The product specifications contained in this publication are issued to provide outline information only which (unless agreed by the company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. Terms and Conditions All products are sold subjects to Zetex' terms and conditions of sale, and this disclaimer (save in the event of a conflict between the two when the terms of the contract shall prevail) according to region, supplied at the time of order acknowledgement. For the latest information on technology, delivery terms and conditions and prices, please contact your nearest Zetex sales office. Quality of product Zetex is an ISO 9001 and TS16949 certified semiconductor manufacturer. To ensure quality of service and products we strongly advise the purchase of parts directly from Zetex Semiconductors or one of our regionally authorized distributors. For a complete listing of authorized distributors please visit: www.zetex.com/salesnetwork Zetex Semiconductors does not warrant or accept any liability whatsoever in respect of any parts purchased through unauthorized sales channels. ESD (Electrostatic discharge) Semiconductor devices are susceptible to damage by ESD. Suitable precautions should be taken when handling and transporting devices. The possible damage to devices depends on the circumstances of the handling and transporting, and the nature of the device. The extent of damage can vary from immediate functional or parametric malfunction to degradation of function or performance in use over time. Devices suspected of being affected should be replaced. Green compliance Zetex Semiconductors is committed to environmental excellence in all aspects of its operations which includes meeting or exceeding regulatory requirements with respect to the use of hazardous substances. Numerous successful programs have been implemented to reduce the use of hazardous substances and/or emissions. All Zetex components are compliant with the RoHS directive, and through this it is supporting its customers in their compliance with WEEE and ELV directives. Product status key: "Preview" Future device intended for production at some point. Samples may be available "Active" Product status recommended for new designs "Last time buy (LTB)" Device will be discontinued and last time buy period and delivery is in effect "Not recommended for new designs" Device is still in production to support existing designs and production "Obsolete" Production has been discontinued Datasheet status key: "Draft version" This term denotes a very early datasheet version and contains highly provisional information, which may change in any manner without notice. "Provisional version" This term denotes a pre-release datasheet. It provides a clear indication of anticipated performance. However, changes to the test conditions and specifications may occur, at any time and without notice. "Issue" This term denotes an issued datasheet containing finalized specifications. However, changes to specifications may occur, at any time and without notice. Zetex sales offices Europe Zetex GmbH Kustermann-Park Balanstrae 59 D-81541 Munchen Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 europe.sales@zetex.com Americas Zetex Inc 700 Veterans Memorial Highway Hauppauge, NY 11788 USA Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 usa.sales@zetex.com Asia Pacific Zetex (Asia Ltd) 3701-04 Metroplaza Tower 1 Hing Fong Road, Kwai Fong Hong Kong Telephone: (852) 26100 611 Fax: (852) 24250 494 asia.sales@zetex.com Corporate Headquarters Zetex Semiconductors plc Zetex Technology Park, Chadderton Oldham, OL9 9LL United Kingdom Telephone: (44) 161 622 4444 Fax: (44) 161 622 4446 hq@zetex.com
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