ZETEX TLV431

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.
TLV431_F (SOT23)
REF 1
3 ANODE
CATHODE 2
The TLV431 can be used as a replacement for
zener diodes in many applications requiring an
improvement in zener performance.
TLV431_H6 (SC70-6)
The TLV431 is available in 2 grades with initial
tolerances of 1% and 0.5% for the A and B
grades respectively.
Features
•
•
•
•
•
•
•
CATHODE 1
6
ANODE
N/C ‡ 2
5
NC ‡
REF 3
4
NC
TLV431_E5 (SOT23-5)
Low Voltage Operation ........... VREF = 1.24V
Temperature range -40 to 125°C
Reference Voltage Tolerance at 25°C
• 0.5%............TLV431B
• 1%...............TLV431A
Typical temperature drift
• 4 mV (0°C to 70°C)
• 6 mV (-40°C to 85°C)
• 11mV (-40°C to 125°C)
80µA Minimum cathode current
0.25Ω Typical Output Impedance
Adjustable Output Voltage ..... VREF to 18V
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
•
•
•
•
Opto-coupler linearisation
Linear regulators
Improved Zener
Variable reference
Order Information
TOL
1%
0.5%
Order code
TLV431AE5TA
TLV431AFTA
TLV431AH6TA
TLV431BE5TA
TLV431BFTA
TLV431BH6TA
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© Zetex Semiconductors plc 2008
Pack
SOT23-5
SOT23
SC70-6
SOT23-5
SOT23
SC70-6
Part
mark
V1A
V1A
V1A
V1B
V1B
V1B
Status
Active
Active
Active
Active
Active
Active
1
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
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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 150°C
Storage Temperature ............................................................... -55 to 150°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.
Package Thermal Data
Package
θJA
PDIS
TA =25°C, TJ = 150°C
SOT23
380°C/W
330 mW
SOT23-5
250°C/W
500 mW
SC70-6
380oC/W
330mW
Recommended Operating Conditions
Min
Max
Units
VKA
Cathode Voltage
VREF
18
V
IKA
Cathode Current
0.1
15
mA
TA
Operating Ambient temperature range
-40
125
°C
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TLV431
Electrical Characteristics
Electrical characteristics over recommended operating conditions, IKA = 10mA, TA = 25°C,
unless otherwise stated.
Symbol
VREF
Parameter
Conditions
Typ
Max
VKA = VREF
TA = 25°C
TLV431A
1.228
1.24
1.252
TLV431B
1.234
1.24
1.246
VKA = VREF
TA = 0 to 70°C
TLV431A
1.221
1.259
TLV431B
1.227
1.253
VKA = VREF
TA = -40 to 85°C
TLV431A
1.215
1.265
TLV431B
1.224
1.259
VKA = VREF
TA = -40 to 125°C
TLV431A
1.209
1.271
TLV431B
1.221
1.265
Reference voltage
Units
V
Deviation of
reference voltage
over full
temperature range
VKA = VREF
ΔVREF
ΔVKA
Ratio of change in
reference voltage
to the change in
cathode voltage
VKA from VREF to
IREF
Reference Input
Current
R1 = 10kΩ R2 = OC
IREF(dev)
IREF deviation over
full temperature
range
R1 = 10kΩ,
R2 = OC
VREF(dev)
Min
TA = 0 to 70°C
4
12
TA = -40 to 85°C
6
20
TA = -40 to 125°C
11
31
-1.5
-2.7
6V
mV
mV/V
18V
-1.5
-2.7
0.15
0.5
TA = 0 to 70°C
0.05
0.3
TA = -40 to 85°C
0.1
0.4
TA = -40 to 125°C
0.15
0.5
TA = 0 to 70°C
55
80
TA = -40 to 85°C
55
80
TA = -40 to 125°C
55
100
µA
µA
Minimum Cathode
current for
regulation
VKA = VREF
IK(OFF)
Off state current
VKA = 18V VREF =0V
0.001
0.1
µA
ZKA
Dynamic Output
Impedance
VKA = VREF f = <1kHz
IK = 0.1 to 15mA
0.25
0.4
Ω
IKMIN
Issue 1 - June 2008
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3
µA
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TLV431
Typical Characteristics
56kΩ 75kΩ I
K
O/P
S1
10mA
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4
10kΩ
100nF
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TLV431
Typical Characteristics
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TLV431
Typical Characteristics
3V
1kΩ
750Ω
470μF
10μF
~
O/P
6.8kΩ IK
© Zetex Semiconductors plc 2008
6
5V
R2
O/P
R1
50Ω
IK
Issue 1 - June 2008
180Ω
4.3kΩ
100μF
~
O/P
0.1mA 1-15mA
R1
1kΩ
100Ω
R2
1kΩ
100Ω
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TLV431
Typical Characteristics
CL
O/P
R
Pulse
generator
f = 100kHz
50Ω
S1
10kΩ I
K
O/P
S2
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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.
IL
R3
VIN
IK
VOUT
R3 =
R1
where
VREF
⎛
R ⎞
VKA = VREF × ⎜⎜ 1 + 1 ⎟⎟
⎝ R2 ⎠
TLV431
C1
0.1µF
VS − VKA
IL + IK
R2
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
Regulated supply
Optocoupler
IF
R1 ⎞
⎛
VOUT = VREF ⎜1 +
⎟
R2 ⎠
⎝
V OUT
To controller
To controller
R3
R1
TLV431
VOUT(max) − 2.7
VOUT − 2.7
> R3 ≥
IF(min)
15mA
R2
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
ZXTP2039F
R1 ⎞
⎛
VOUT = VREF ⎜1 +
⎟
2⎠
R
⎝
R1
Q1
V
R3 =
REF
TLV431
C1
0.1µF
VIN − (VOUT + VBE )
IB
⎛ ISH
⎜
⎜ hFE(min)
⎝
R2
ISH
⎞
⎟ < IB ≤ 15mA
⎟
⎠
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
I
OUT
VIN
IB
R3
VOUT
Q1
R1 ⎞
⎛
VOUT = VREF ⎜1 +
⎟
R2 ⎠
⎝
R1
I
R3 =
K
V
REF
VIN − ( VOUT + VBE )
IB +IK
TLV431
C1
0.1µF
⎛ IOUT(max)
⎜
⎜ hFE(min)
⎝
R2
⎞
⎟ < 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.
ZXTN25020CFH
VIN
IB
R3
Q1
TLV431
Rs
IOUT
VREF
R1 ⎞
⎛
VOUT = VREF ⎜1 +
⎟
R
2⎠
⎝
R3 =
VIN − ( VOUT + VBE )
IB +IK
R1
V REF
⎛ I OUT (max) ⎞
⎜
⎟ < I B ≤ 15mA
⎜ h
⎟
⎝ FE (min) ⎠
TLV431
C1
0.1µF
VOUT
R2
RS =
VREF
IOUT (max)
GND
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
VOUT
VOUT
VIN
GND
R1
VOUT ≥ (VREG + VREF )
VREG
Volt Reg
R1 ⎞
⎛
VOUT = VREF ⎜1 +
⎟
R
2⎠
⎝
VREF
TLV431
(All features of the regulator such
C1
0.1µF
R2
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
Vin
VOUT
VR1 Vout
VOUT ≥ (VREG + VREF )
GND
IB
R1 ⎞
⎛
VOUT = VREF ⎜1 +
⎟
R
2⎠
⎝
R3
1.2V
R1
VREF
VIN − (VOUT − VREG )
IB
0.1mA ≤ I B ≤ 15mA
TLV431
C1
0.1µF
R3 =
(All features of the regulator such as short
R2
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
Flag
V+
V+
Flag
VIN
ISH
R1
VREF
VIN
TLV431
R2
VTH
1.24
GND
t
0
R1 ⎞
⎛
VTH = VREF ⎜1 +
⎟
R2 ⎠
⎝
R3 =
V + − 1.24
I SH
0.1mA ≤ I SH ≤ 18mA
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
SOT23-5
E
e
e1
b
3 leads
L1
D
E1
A
L
A1
c
Dimension Table SOT23
Dim.
Millimeters
Inches
Dim.
Millimeters
Max.
Min.
Max.
A
-
1.12
-
0.044
e1
A1
0.01
0.10
0.0004
0.004
E
2.10
2.64
0.083
0.104
b
0.30
0.50
0.012
0.020
E1
1.20
1.40
0.047
0.055
c
0.085
0.20
0.003
0.008
L
0.25
0.60
0.0098
0.0236
D
2.80
3.04
0.110
0.120
L1
0.45
0.62
0.018
0.024
-
-
-
-
-
e
0.95 NOM
Min.
Inches
Min.
0.037 NOM
Max.
Min.
1.90 NOM
Max.
0.075 NOM
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
Dimension table - SOT23-5
Dim.
Millimeters
Inches
Dim.
Min.
Max.
Min.
Max.
A
0.9
1.45
0.0354
0.0570
A1
0.00
0.15
0.00
A2
0.90
1.3
b
0.20
C
0.09
D
2.70
Millimeters
Inches
Min.
Max.
Min.
Max.
E
2.20
3.20
0.0866
0.1181
0.0059
E1
1.30
1.80
0.0511
0.0708
0.0354
0.0511
e
0.95 REF
0.0374
0.50
0.0078
0.0196
e1
1.90 REF
0.0748
0.26
0.0035
0.0102
L
0.10
0.60
0.0039
0.0236
0.1220
ao
0
30
0
30
3.10
0.1062
Note: Controlling dimensions are in millimeters. Approximate dimensions are provided in inches
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TLV431
Package outline - SC70-6
␣
Dim.
Millimeters
Inches
Dim.
Millimeters
Max.
Min.
Max.
A
0.80
1.10
0.0315
0.0433
E
2.10 BSC
0.0826 BSC
A1
0
0.10
0
0.0039
E1
1.25 BSC
0.0492 BSC
A2
0.80
1.00
0.0315
0.0394
e
0.65 BSC
0.0255 BSC
b
0.15
0.30
0.006
0.0118
e1
1.30 BSC
0.0511 BSC
C
0.08
0.25
0.0031
0.0098
L
0.26
0.46
0.0102
0.0181
ao
0
8
0
8
D
2.00 BSC
Min.
0.0787 BSC
Max.
Inches
Min.
Min.
Max.
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.
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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.
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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.
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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
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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.
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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.
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© 2008 Published by Zetex Semiconductors plc
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