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TL431LI
TL432LI
SLVSDQ6A – JULY 2018 – REVISED NOVEMBER 2018
TL431LI / TL432LI Programmable Shunt Regulator with Optimized Reference Current
1 Features
3 Description
•
The TL431LI device is a three-terminal adjustable
shunt regulator, with specified thermal stability over
applicable automotive, commercial, and military
temperature ranges. The output voltage can be set to
any value between Vref (approximately 2.495 V) and
36 V, with two external resistors. These devices have
a typical output impedance of 0.3 Ω. Active output
circuitry provides a very sharp turn-on characteristic,
making these devices excellent replacements for
Zener diodes in many applications, such as onboard
regulation, adjustable power supplies, and switching
power supplies. This device is a pin-to-pin alternative
to the industry standard TL431, with optimized Iref and
IIdev performance. The lower Iref and IIdev values
enable designers to achieve higher system accuracy
and lower leakage current. The TL432LI device has
exactly the same functionality and electrical
specifications as the TL431LI device, but has a
different pinout for the DBZ package.
1
•
•
•
•
•
•
•
•
Reference Voltage Tolerance at 25°C
– 0.5% (B Grade)
– 1% (A Grade)
Minimum Typical Output Voltage: 2.495 V
Adjustable Output Voltage: Vref to 36 V
Operation From −40°C to +125°C (Q Temp)
Maximum Temperature Drift
– 10 mV (C Temp)
– 17 mV (I Temp)
– 27 mV (Q Temp)
0.3-Ω Typical Output Impedance
Sink-Current Capability
– Imin = 1 mA (max)
– IKA = 15 mA (max)
Reference Input Current IREF: 0.4 μA (max)
Deviation of Reference Input Current over
Temperature, II(dev): 0.3 μA (max)
The TL431LI device is offered in two grades, with
initial tolerances (at 25°C) of 0.5% and 1%, for the B
and A grade, respectively. In addition, low output drift
versus temperature ensures good stability over the
entire temperature range.
2 Applications
•
•
•
•
•
•
Adjustable Voltage and Current Referencing
Secondary Side Regulation in Flyback SMPS
Zener Diode Replacement
Voltage Monitoring
Precision Constant Current Sink/Source
Comparator with Integrated Reference
The TL43xLIxQ devices are
operation from –40°C to 125°C.
characterized
for
Device Information(1)
PART NUMBER
TL43xLI
PACKAGE (PIN)
SOT-23 (3)
BODY SIZE (NOM)
2.90 mm x 1.30 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Simplified Schematic
VKA
Input
IKA
Vref
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
TL431LI
TL432LI
SLVSDQ6A – JULY 2018 – REVISED NOVEMBER 2018
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Device Comparison Table.....................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
4
7.1
7.2
7.3
7.4
7.5
7.6
4
4
4
4
5
6
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Thermal Information ..................................................
Recommended Operating Conditions.......................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Parameter Measurement Information .................. 9
8.1 Temperature Coefficient............................................ 9
8.2 Dynamic Impedance ............................................... 10
9
Detailed Description ............................................ 11
9.1 Overview ................................................................. 11
9.2 Functional Block Diagram ....................................... 11
9.3 Feature Description................................................. 12
9.4 Device Functional Modes........................................ 12
10 Applications and Implementation...................... 13
10.1 Application Information.......................................... 13
10.2 Typical Applications .............................................. 13
10.3 System Examples ................................................. 21
11 Power Supply Recommendations ..................... 24
12 Layout................................................................... 24
12.1 Layout Guidelines ................................................. 24
12.2 Layout Example .................................................... 25
13 Device and Documentation Support ................. 26
13.1
13.2
13.3
13.4
13.5
13.6
13.7
Related Links ........................................................
Documentation Support ........................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
26
26
26
26
27
27
27
14 Mechanical, Packaging, and Orderable
Information ........................................................... 27
4 Revision History
Changes from Original (July 2018) to Revision A
•
2
Page
Changed TL43xLI status from Advance Information to Production Data release ................................................................. 1
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5 Device Comparison Table
DEVICE PINOUT
INITIAL ACCURACY
OPERATING FREE-AIR TEMPERATURE (TA)
TL431LI
TL432LI
A: 1%
B: 0.5%
C: 0°C to 70°C
I: -40°C to 85°C
Q: -40°C to 125°C
6 Pin Configuration and Functions
TL431LI DBZ Package
3-Pin SOT-23
Top View
CATHODE
TL432LI DBZ Package
3-Pin SOT-23
Top View
1
3
ANODE
REF
1
CATHODE
2
3
ANODE
2
REF
Pin Functions
PIN NUMBER
NAME
TL431LIx
TL432LIx
DBZ
DBZ
TYPE
DESCRIPTION
ANODE
3
3
O
Common pin, normally connected to ground
CATHODE
1
2
I/O
Shunt Current/Voltage input
REF
2
1
I
Threshold relative to common anode
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
VKA
Cathode Voltage (2)
IKA
Continuos Cathode Current Range
II(ref)
Reference Input Current
TJ
Tstg
(1)
(2)
MAX
UNIT
37
V
–10
18
mA
–5
10
mA
Operating Junction Temperature Range
–40
150
C
Storage Temperature Range
–65
150
C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltage values are with respect to ANODE, unless otherwise noted.
7.2 ESD Ratings
VALUE
Electrostatic
discharge
V(ESD)
(1)
(2)
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001pins (1)
±2000
Charged-device model (CDM), per JEDEC specification JESD22- ±1000
VC101 (2)
±1000
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
7.3 Thermal Information
TL43xLI
THERMAL METRIC (1)
DBZ
UNIT
3 PINS
RθJA
Junction-to-ambient thermal resistance
371.7
C/W
RθJC(top)
Junction-to-case (top) thermal resistance
145.9
C/W
RθJB
Junction-to-boardthermal resistance
104.7
C/W
ψJT
Junction-to-top characterization resistance
23.9
C/W
ψJB
Junction-to-board characterization resistance
102.9
C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
7.4 Recommended Operating Conditions
See
(1)
VKA
Cathode Voltage
IKA
Continuous Cathode Current Range
MIN
MAX
VREF
36
V
1
15
mA
0
70
C
TL43xLIxI
–40
85
C
TL43xLIxQ
–40
125
C
TL43xLIxC
TA
(1)
4
Operating Free-Air Temperature
UNIT
Maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any allowable ambient
temperature is PD = (TJ(max) – TA)/θJA. Operating at the absolute maximum TJ of 150°C can affect reliability.
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7.5 Electrical Characteristics
over recommended operating conditions, TA = 25°C (unless otherwise noted)
PARAMETER
Vref
TEST CIRCUIT
Reference Voltage
See Figure 14
Deviation of reference
input voltage over full
temperature range (1)
ΔVref /
ΔVKA
Ratio of change in
reference voltage to the
change in cathode
voltage
Iref
Reference Input Current See Figure 15
II(dev)
Deviation of reference
input current over full
temperature range (1)
Imin
Minimum cathode
current for regulation
Ioff
Off-state cathode
current
|ZKA|
(1)
(2)
Dynamic Impedance
VKA = Vref, IKA = 1 mA
MIN
See Figure 14
VKA = Vref, IKA = 1 mA
TYP MAX
UNIT
TL43xLIAx devices
2470 2495 2520
mV
TL43xLIBx devices
2483 2495 2507
mV
TL43xLIxC devices
VI(dev)
(2)
TEST CONDITIONS
TL43xLIxI devices
TL43xLIxQ devices
2.5
11
mV
6
17
mV
10
27
–1.4
–2.7
mV/V
–1
–2
mV/V
IKA = 1 mA, R1 = 10kΩ, R2 = ∞
0.2
0.4
µA
See Figure 15
IKA = 1 mA, R1 = 10kΩ, R2 = ∞
0.1
0.3
µA
See Figure 14
VKA = Vref
1
mA
See Figure 16
VKA = 36 V, Vref = 0
0.1
1
µA
See Figure 14
VKA = Vref, IKA = 1 mA to 15 mA
0.3
0.65
Ω
ΔVKA = 10 V - Vref
See Figure 15
IKA = 1 mA
ΔVKA = 36 V - 10 V
mV
The deviation parameters VI(dev) and II(dev) are defined as the differences between the maximum and minimum values obtained over the
rated temperature range. For more details on VI(dev) and how it relates to the average temperature coefficient, see Parameter
Measurement Information.
The dynamic impedance is defined by |ZKA| = ΔVKA/ΔIKA. For more details on |ZKA| and how it relates to VKA, see Parameter
Measurement Information.
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7.6 Typical Characteristics
Data at high and low temperatures are applicable only within the recommended operating free-air temperature
ranges of the various devices.
1
2.5005
0.9
Iref - Reference Current - µA
Vref - Reference Voltage - V
Vka = Vref
2.499 I = 1 mA
KA
2.4975
2.496
2.4945
2.493
2.4915
2.49
2.4885
0.7
0.6
0.5
0.4
0.3
0.2
0
-50
-25
0
25 50 75 100 125 150
TA - Free-Air Temperature - °C
D001
Book
Figure 1. Reference Voltage vs Free-Air Temperature
-25
0
25
50
75 100
TA - Free-Air Temperature - °C
125
D002
Figure 2. Reference Current vs Free-Air Temperature
0.064
15
VKA = Vref
TA = 25°C
12
Ioff - Off-State Cathode Current - PA
IKA - Cathode Current - mA
0.8
0.1
2.487
2.4855
-50
IKA = 1 mA
9
6
3
0
0.5
1
1.5
2
2.5
VKA - Cathode Voltage -V
0.048
0.04
0.032
0.024
0.016
0.008
0
-50
-3
0
VKA = 36 V
0.056 VREF = 0 V
3
-25
0
25
50
75 100
TA - Free-Air Temperature - °C
125
D003
D004
Figure 4. Off-State Cathode Current
vs Free-Air Temperature
Figure 3. Cathode Current vs Cathode Voltage
-1.05
VKA = 3 V to 36 V
Y AXIS TITLE (Unit)
-1.2
-1.35
-1.5
-1.65
-1.8
-50
-25
0
25
50
75
Temperature (°C)
100
125
D006
Figure 5. Ratio of Delta Reference Voltage to Delta Cathode Voltage vs Free-Air Temperature
6
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75
IKA = 10 mA
TA = 25°C
200
Gain
Phase
60
160
45
120
30
80
15
Phase - Degrees
AV - Small-Signal Voltage Amplification - dB
Typical Characteristics (continued)
Output
IKA
15 kΩ
9 µF
+
40
−
8.25 kΩ
0
100
1k
10k
100k
f - Frequency - Hz
0
10M
1M
Gain
Figure 6. Small-Signal Voltage Amplification
vs Frequency
GND
Figure 7. Test Circuit for Voltage Amplification
100
|ZKA| - Reference Impedance - Ohms
232 Ω
1 kΩ
IKA = 10 mA
50 T = 25°C
A
30
20
Output
IKA
10
50 Ω
5
3
2
−
+
1
GND
0.5
0.3
0.2
0.1
1k
10k
100k
f - Frequency - Hz
1M
D005
Figure 9. Test Circuit for Reference Impedance
Figure 8. Reference Impedance vs Frequency
6
Input and Output Voltage - V
Input
220 Ω
TA = 25qC
Output
5
4
3
Pulse
Generator
f = 100 kHz
Output
2
50 Ω
1
GND
0
-1
0
1
2
3
4
t - Time - Ps
5
6
7
puls
Figure 10. Pulse Response
Figure 11. Test Circuit for Pulse Response
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Typical Characteristics (continued)
150 Ω
IKA - Cathode Current - mA
15
12
A VKA = Vref
B VKA = 5 V
C VKA = 10 V
IKA
+
VBATT
CL
Stable Region
−
9
6
TEST CIRCUIT FOR CURVE A
3
0
0.001
IKA
0.01
0.1
1
CL - Load Capacitance - µF
R1 = 10 kΩ
10
Copy
TL43
The areas under the curves represent conditions that may cause the
device to oscillate. For curves B and C, R2 and V+ are adjusted to
establish the initial VKA and IKA conditions, with CL = 0. VBATT and CL
then are adjusted to determine the ranges of stability.
Figure 12. Stability Boundary Conditions for All TL431LI,
TL432LI Devices
150 Ω
CL
+
R2
VBATT
−
TEST CIRCUIT FOR CURVES B, C, AND D
Figure 13. Test Circuits for Stability Boundary Conditions
8
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8 Parameter Measurement Information
VKA
Input
IKA
Vref
Figure 14. Test Circuit for VKA = Vref
Input
VKA
IKA
R1
Iref
R2
Vref
R1 ö
æ
VKA = Vref ç 1 +
÷ + Iref × R1
R2 ø
è
Figure 15. Test Circuit for VKA > Vref
Input
VKA
Ioff
Figure 16. Test Circuit for Ioff
8.1 Temperature Coefficient
The deviation of the reference voltage, Vref, over the full temperature range is known as VI(dev). The parameter of
VI(dev) can be used to find the temperature coefficient of the device. The average full-range temperature
coefficient of the reference input voltage, αVref, is defined as:
αVref is positive or negative, depending on whether minimum Vref or maximum Vref, respectively, occurs at the
lower temperature. The full-range temperature coefficient is an average and therefore any subsection of the rated
operating temperature range can yield a value that is greater or less than the average. For more details on
temperature coefficient, check out Voltage Reference Selection Basics.
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8.2 Dynamic Impedance
'VKA
'IKA . When the device is operating with two external resistors
The dynamic impedance is defined as:
'V
z'
'I which is approximately equal to
(see Figure 15), the total dynamic impedance of the circuit is given by:
R1 ·
§
ZKA ¨ 1
¸
© R2 ¹ .
ZKA
Itest
P/
IKA (mA)
The VKA of the TL431LI can be affected by the dynamic impedance. The TL431LI test current Itest for VKA is
specified on the Eletrical Characteristics . Any deviation from Itest can cause deviation on the output VKA.
Figure 17 shows the effect of the dynamic impedance on the VKA.
IKA
IKA(min)
0
VKA (V)
Ps
Figure 17. Dynamic Impedance
10
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9 Detailed Description
9.1 Overview
This standard device has proven ubiquity and versatility across a wide range of applications, ranging from power
to signal path. This is due to its key components containing an accurate voltage reference and op amp, which
are very fundamental analog building blocks. TL43xLI is used in conjunction with it's key components to behave
as a single voltage reference, error amplifier, voltage clamp or comparator with integrated reference.
TL43xLI can be operated and adjusted to cathode voltages from 2.495V to 36V, making this part optimum for a
wide range of end equipments in industrial, auto, telecom and computing. In order for this device to behave as a
shunt regulator or error amplifier, >1mA (Imin(max)) must be supplied in to the cathode pin. Under this condition,
feedback can be applied from the Cathode and Ref pins to create a replica of the internal reference voltage.
Various reference voltage options can be purchased with initial tolerances (at 25°C) of 0.5%, and 1%. These
reference options are denoted by B (0.5%) and A (1.0%) after the TL431LI or TL432LI. TL431LI and TL432LI are
both functionally the same, but have separate pinout options.
The TL43xLIxC devices are characterized for operation from 0°C to 70°C, the TL43xLIxI devices are
characterized for operation from –40°C to 85°C, and the TL43xLIxQ devices are characterized for operation from
–40°C to 125°C.
9.2 Functional Block Diagram
CATHODE
+
REF
_
Vref
ANODE
Figure 18. Equivalent Schematic
CATHODE
REF
ANODE
Figure 19. Detailed Schematic
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9.3 Feature Description
TL43xLI consists of an internal reference and amplifier that outputs a sink current based on the difference
between the reference pin and the virtual internal pin. The sink current is produced by the internal Darlington
pair, shown in the above schematic (Figure 19). A Darlington pair is used in order for this device to be able to
sink a maximum current of 15 mA.
When operated with enough voltage headroom (≥ 2.495 V) and cathode current (IKA), TL43xLI forces the
reference pin to 2.495 V. However, the reference pin can not be left floating, as it needs IREF ≥ 0.4 µA (please
see Specifications). This is because the reference pin is driven into an npn, which needs base current in order
operate properly.
When feedback is applied from the Cathode and Reference pins, TL43xLI behaves as a Zener diode, regulating
to a constant voltage dependent on current being supplied into the cathode. This is due to the internal amplifier
and reference entering the proper operating regions. The same amount of current needed in the above feedback
situation must be applied to this device in open loop, servo or error amplifying implementations in order for it to
be in the proper linear region giving TL43xLI enough gain.
Unlike many linear regulators, TL43xLI is internally compensated to be stable without an output capacitor
between the cathode and anode. However, if it is desired to use an output capacitor Figure 12 can be used as a
guide to assist in choosing the correct capacitor to maintain stability.
9.4 Device Functional Modes
9.4.1 Open Loop (Comparator)
When the cathode/output voltage or current of TL43xLI is not being fed back to the reference/input pin in any
form, this device is operating in open loop. With proper cathode current (Ika) applied to this device, TL43xLI will
have the characteristics shown in Figure 18. With such high gain in this configuration, TL43xLI is typically used
as a comparator. With the reference integrated makes TL43xLI the preferred choice when users are trying to
monitor a certain level of a single signal. Look at SLVA987 for more details on open loop comparator applications
on the TL431LI.
9.4.2 Closed Loop
When the cathode/output voltage or current of TL43xLI is being fed back to the reference/input pin in any form,
this device is operating in closed loop. The majority of applications involving TL43xLI use it in this manner to
regulate a fixed voltage or current. The feedback enables this device to behave as an error amplifier, computing
a portion of the output voltage and adjusting it to maintain the desired regulation. This is done by relating the
output voltage back to the reference pin in a manner to make it equal to the internal reference voltage, which can
be accomplished through resistive or direct feedback.
12
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10 Applications and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
10.1 Application Information
As this device has many applications and setups, there are many situations that this datasheet can not
characterize in detail. The linked application notes help the designer make the best choices when using this part.
Application note Designing with the Improved TL431LI, SNOAA00 provides a deeper understanding of this
device's accuracy in a flyback optocoupler application. Application note Setting the Shunt Voltage on an
Adjustable Shunt Regulator, SLVA445 assists designers in setting the shunt voltage to achieve optimum
accuracy for this device.
10.2 Typical Applications
10.2.1 Comparator With Integrated Reference
Vsup
Rsup
Vout
CATHODE
R1
VIN
RIN
REF
VL
+
R2
2.5V
ANODE
Figure 20. Comparator Application Schematic
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Typical Applications (continued)
10.2.1.1 Design Requirements
For this design example, use the parameters listed in Table 1 as the input parameters.
Table 1. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Input Voltage Range
0 V to 5 V
Input Resistance
10 kΩ
Supply Voltage
24 V
Cathode Current (Ik)
5 mA
Output Voltage Level
~2 V – VSUP
Logic Input Thresholds VIH/VIL
VL
10.2.1.2 Detailed Design Procedure
When using TL43xLI as a comparator with reference, determine the following:
• Input Voltage Range
• Reference Voltage Accuracy
• Output logic input high and low level thresholds
• Current Source resistance
10.2.1.2.1 Basic Operation
In the configuration shown in Figure 20 TL43xLI will behave as a comparator, comparing the VREF pin voltage to
the internal virtual reference voltage. When provided a proper cathode current (IK), TL43xLI will have enough
open loop gain to provide a quick response. This can be seen in Figure 21, where the RSUP=10 kΩ (IKA=500 µA)
situation responds much slower than RSUP=1 kΩ (IKA=5 mA). With the TL43xLI max Operating Current (IMIN)
being 1 mA, operation below that could result in low gain, leading to a slow response.
10.2.1.2.1.1 Overdrive
Slow or inaccurate responses can also occur when the reference pin is not provided enough overdrive voltage.
This is the amount of voltage that is higher than the internal virtual reference. The internal virtual reference
voltage will be within the range of 2.495 V ±(0.5% or 1.0%) depending on which version is being used. The more
overdrive voltage provided, the faster the TL43xLI will respond.
For applications where TL43xLI is being used as a comparator, it is best to set the trip point to greater than the
positive expected error (that is +1.0% for the A version). For fast response, setting the trip point to >10% of the
internal VREF should suffice.
For minimal voltage drop or difference from Vin to the ref pin, TI recommends to use an input resistor