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LM3411
SNVS113F – DECEMBER 1999 – REVISED MAY 2016
LM3411 Precision Secondary Regulator and Driver
1 Features
3 Description
•
The LM3411 is a low-power fixed-voltage (3.3 V or
5 V) precision shunt regulator designed specifically
for driving an optoisolator to provide feedback
isolation in a switching regulator.
1
•
•
•
•
Fixed Voltages of 3.3 V and 5 V With Initial
Tolerance of ±1% for Standard Grade and ±0.5%
for A Grade
Custom Voltages Available (3 V to 17 V)
Wide Output Current Range (20 μA to 15 mA)
Low Temperature Coefficient
Available in 5-Pin SOT-23 Surface-Mount
Package (Tape and Reel)
2 Applications
•
•
•
•
Secondary Controller for Isolated DC-DC PWM
Switching Regulators Systems
Use With LDO Regulator for High-Precision,
Fixed-Output Regulators
Precision Monitoring Applications
Use With Many Types of Regulators to Increase
Precision and Improve Performance
The LM3411 circuitry includes an internally
compensated operational amplifier, a bandgap
reference, NPN output transistor, and voltage setting
resistors.
A trimmed precision bandgap reference with
temperature drift curvature correction provides a
ensured 1% precision over the operating temperature
range (A grade version). The inverting input of the
amplifier is externally accessible for loop frequency
compensation when used as part of a larger servo
system. The output is an open-emitter NPN transistor
capable of driving up to 15 mA of load current.
Because of its small die size, the LM3411 has been
made available in the subminiature 5-pin SOT-23
surface-mount package. This package is ideal for use
in space-critical applications.
Although its main application is to provide a precision
output voltage (no trimming required) and maintain
very good regulation in isolated DC-DC converters, it
can also be used with other types of voltage
regulators or power semiconductors to provide a
precision output voltage without precision resistors or
trimming.
Device Information(1)
PART NUMBER
LM3411
PACKAGE
SOT-23 (5)
BODY SIZE (NOM)
2.90 mm × 1.60 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application Schematic
LM3411 Functional Diagram
Copyright © 2016, Texas Instruments Incorporated
Copyright © 2016, Texas Instruments Incorporated
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.
LM3411
SNVS113F – DECEMBER 1999 – REVISED MAY 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
4
6.1
6.2
6.3
6.4
6.5
6.6
6.7
4
4
4
4
5
6
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics: 3.3-V Version...................
Electrical Characteristics: 5-V Version......................
Typical Characteristics ..............................................
Parameter Measurement Information .................. 9
Detailed Description ............................................ 11
8.1 Overview ................................................................. 11
8.2 Functional Block Diagrams ..................................... 11
8.3 Feature Description................................................. 12
8.4 Device Functional Modes........................................ 12
9
Application and Implementation ........................ 13
9.1 Application Information............................................ 13
9.2 Typical Applications ................................................ 13
10 Power Supply Recommendations ..................... 24
11 Layout................................................................... 24
11.1 Layout Guidelines ................................................. 24
11.2 Layout Example .................................................... 24
12 Device and Documentation Support ................. 25
12.1
12.2
12.3
12.4
12.5
Documentation Support ........................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
25
25
25
25
25
13 Mechanical, Packaging, and Orderable
Information ........................................................... 25
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision E (April 2013) to Revision F
•
Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section .................................................................................................. 1
Changes from Revision D (April 2013) to Revision E
•
2
Page
Page
Changed layout of National Semiconductor Data Sheet to TI format .................................................................................. 12
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SNVS113F – DECEMBER 1999 – REVISED MAY 2016
5 Pin Configuration and Functions
DBV Package
5-Pin SOT-23
Top View
+IN
1
GND
2
²
3
5
OUT
4
COMP
Pin Functions
PIN
NO.
NAME
I/O
DESCRIPTION
1
+IN
I
2
GND
I/O
Output measurement pin
Ground pin
3
—
—
No internal connection, but must be soldered to printed-circuit board for best heat transfer.
4
COMP
I/O
Operational amplifier inverting input pin
5
OUT
O
Optocoupler drive pin
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SNVS113F – DECEMBER 1999 – REVISED MAY 2016
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
MAX
UNIT
20
V
Input voltage, VIN
Output current
20
mA
Power dissipation (TA = 25°C) (3)
300
mW
Lead temperature
Vapor phase (60 s)
215
Infrared (15 s)
220
Junction temperature
Storage temperature, Tstg
(1)
(2)
(3)
–65
°C
150
°C
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.
See AN-450 Surface Mounting Methods and Their Effect on Product Reliability (SNOA742) for methods on soldering surface-mount
devices.
The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature),
RθJA (junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any
temperature is (PDmax = TJmax – TA) / RθJA or the number given in the Absolute Maximum Ratings, whichever is lower. The typical
thermal resistance (RθJA) when soldered to a printed-circuit board is approximately 306°C/W for the DBV package.
6.2 ESD Ratings
V(ESD)
(1)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001
VALUE
UNIT
±1500
V
(1)
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted) (1)
MIN
VI
Input voltage
IO
Output current
TA
Ambient temperature
TJ
Operating junction temperature
(1)
LM3411x 3.3-V
NOM
MAX
3.3
LM3411x 5-V
V
5
0
UNIT
15
mA
–40
85
°C
–40
125
°C
The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature),
RθJA (junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any
temperature is (PDmax = TJmax − TA)/RθJA or the number given in the Absolute Maximum Ratings, whichever is lower. The typical thermal
resistance (RθJA) when soldered to a printed-circuit board is approximately 306°C/W for the DBV package.
6.4 Thermal Information
LM3411
THERMAL METRIC (1)
DBV (SOT-23)
UNIT
5 PINS
RθJA
Junction-to-ambient thermal resistance
178.6
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
134.7
°C/W
RθJB
Junction-to-board thermal resistance
37.3
°C/W
ψJT
Junction-to-top characterization parameter
24.7
°C/W
ψJB
Junction-to-board characterization parameter
36.8
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
—
°C/W
(1)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
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6.5 Electrical Characteristics: 3.3-V Version
Specifications are for TJ = 25°C, VIN = VREG, and VOUT = 1.5 V (unless otherwise noted).
PARAMETER
LM3411A 3.3-V
Regulation voltage
IOUT = 5 mA
LM3411 3.3-V
VREG
LM3411A 3.3-V
Regulation voltage
tolerance
IOUT = 5 mA
LM3411 3.3-V
LM3411A 3.3-V
Iq
Quiescent current
IOUT = 5 mA
LM3411 3.3-V
LM3411A 3.3-V
20 μA ≤ IOUT ≤ 1 mA
LM3411 3.3-V
Gm
Transconductance
ΔIOUT/ΔVREG
LM3411A 3.3-V
1 mA ≤ IOUT ≤ 15 mA
LM3411 3.3-V
LM3411A 3.3-V
RL = 140 Ω
(3)
LM3411 3.3-V
AV
Voltage gain
ΔVOUT/ΔVREG
LM3411A 3.3-V
RL = 2 kΩ
LM3411 3.3-V
LM3411A 3.3-V
VSAT
Output
saturation (4)
VIN = VREG + 100 mV,
IOUT = 15 mA
LM3411 3.3-V
LM3411A 3.3-V
IL
Output leakage
current
VIN = VREG – 100 mV,
VOUT = 0 V
LM3411 3.3-V
Rf
Internal feedback
resistor
En
Output noise
voltage
(1)
(2)
(3)
(4)
MIN (1)
TYP (2)
MAX (1)
TJ = 25°C
3.284
3.3
3.317
–40°C ≤ TJ ≤ 125°C
3.267
TJ = 25°C
3.267
–40°C ≤ TJ ≤ 125°C
3.234
TEST CONDITIONS
3.333
3.3
3.333
3.366
TJ = 25°C
±1%
TJ = 25°C
±1%
–40°C ≤ TJ ≤ 125°C
±2%
TJ = 25°C
85
–40°C ≤ TJ ≤ 125°C
85
–40°C ≤ TJ ≤ 125°C
TJ = 25°C
3.3
0.75
1
0.5
TJ = 25°C
3.3
3.3
mA/mV
6
2
TJ = 25°C
2.5
–40°C ≤ TJ ≤ 125°C
1.7
TJ = 25°C,
1 V ≤ VOUT ≤ VREG – 1.2 V
550
−40°C ≤ TJ ≤ 125°C,
1 V ≤ VOUT ≤ VREG – 1.3 V
250
TJ = 25°C,
1 V ≤ VOUT ≤ VREG – 1.2 V
450
−40°C ≤ TJ ≤ 125°C,
1 V ≤ VOUT ≤ VREG – 1.3 V
200
TJ = 25°C,
1 V ≤ VOUT ≤ VREG – 1.2 V
1500
−40°C ≤ TJ ≤ 125°C,
1 V ≤ VOUT ≤ VREG – 1.3 V
900
TJ = 25°C,
1 V ≤ VOUT ≤ VREG – 1.2 V
1000
−40°C ≤ TJ ≤ 125°C,
1 V ≤ VOUT ≤ VREG – 1.3 V
700
6
1000
1000
V/V
TJ = 25°C
3500
3500
1
–40°C ≤ TJ ≤ 125°C
1.2
1.3
TJ = 25°C
1
–40°C ≤ TJ ≤ 125°C
1.2
V
1.3
TJ = 25°C
0.1
0.5
0.1
0.5
–40°C ≤ TJ ≤ 125°C
1
TJ = 25°C
–40°C ≤ TJ ≤ 125°C
μA
1
LM3411A 3.3-V
39
52
65
LM3411 3.3-V
39
52
65
IOUT = 1 mA, 10 Hz ≤ f ≤ 10 kHz
μA
125
150
1.5
–40°C ≤ TJ ≤ 125°C
–40°C ≤ TJ ≤ 125°C
110
115
TJ = 25°C
–40°C ≤ TJ ≤ 125°C
V
±0.5%
–40°C ≤ TJ ≤ 125°C
TJ = 25°C
UNIT
50
kΩ
μVRMS
Limits are 100% production tested at 25°C. Limits over the operating temperature range are ensured through correlation using Statistical
Quality Control (SQC) methods. The limits are used to calculate TIs Averaging Outgoing Level (AOQL).
Typical numbers are at 25°C and represent the most likely parametric norm.
Actual test is done using equivalent current sink instead of a resistor load.
VSAT = VIN – VOUT, when the voltage at the IN pin is forced 100 mV above the nominal regulating voltage (VREG).
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6.6 Electrical Characteristics: 5-V Version
Specifications are for TJ = 25°C, VIN = VREG, and VOUT = 1.5 V (unless otherwise noted).
PARAMETER
TEST CONDITIONS
LM3411A 5-V
Regulation voltage
IOUT = 5 mA
LM3411 5-V
VREG
LM3411A 5-V
Regulation voltage
tolerance
IOUT = 5 mA
LM3411 5-V
LM3411A 5-V
Iq
Quiescent current
IOUT = 5 mA
LM3411 5-V
LM3411A 5-V
20 μA ≤ IOUT ≤ 1 mA
LM3411 5-V
Gm
Transconductance
ΔIOUT/ΔVREG
LM3411A 5-V
1 mA ≤ IOUT ≤ 15 mA
LM3411 5-V
LM3411A 5-V
RL = 250 Ω
(3)
LM3411 5-V
AV
Voltage gain
ΔVOUT/ΔVREG
LM3411A 5-V
RL = 2 kΩ
LM3411 5-V
LM3411A 5-V
VSAT
Output
saturation (4)
VIN = VREG + 100 mV,
IOUT = 15 mA
LM3411 5-V
LM3411A 5-V
IL
Output leakage
current
VIN = VREG – 100 mV,
VOUT = 0 V
LM3411 5-V
Rf
Internal feedback
resistor
En
Output noise
voltage
(1)
(2)
(3)
(4)
6
TJ = 25°C
MIN (1)
TYP (2)
MAX (1)
4.975
5
5.025
–40°C ≤ TJ ≤ 125°C
4.95
TJ = 25°C
4.95
–40°C ≤ TJ ≤ 125°C
UNIT
5.05
5
4.9
5.05
5.1
TJ = 25°C
±0.5%
–40°C ≤ TJ ≤ 125°C
±1%
TJ = 25°C
±1%
–40°C ≤ TJ ≤ 125°C
V
±2%
TJ = 25°C
85
–40°C ≤ TJ ≤ 125°C
110
115
TJ = 25°C
85
–40°C ≤ TJ ≤ 125°C
125
μA
150
TJ = 25°C
1.5
–40°C ≤ TJ ≤ 125°C
3.3
0.75
TJ = 25°C
1
–40°C ≤ TJ ≤ 125°C
0.5
TJ = 25°C
3.3
–40°C ≤ TJ ≤ 125°C
3.3
mA/mV
6
2
TJ = 25°C
2.5
–40°C ≤ TJ ≤ 125°C
1.7
TJ = 25°C,
1 V ≤ VOUT ≤ VREG – 1.2 V
750
−40°C ≤ TJ ≤ 125°C,
1 V ≤ VOUT ≤ VREG – 1.3 V
350
TJ = 25°C,
1 V ≤ VOUT ≤ VREG – 1.2 V
650
−40°C ≤ TJ ≤ 125°C,
1 V ≤ VOUT ≤ VREG – 1.3 V
300
TJ = 25°C,
1 V ≤ VOUT ≤ VREG – 1.2 V
1500
−40°C ≤ TJ ≤ 125°C,
1 V ≤ VOUT ≤ VREG – 1.3 V
900
TJ = 25°C,
1 V ≤ VOUT ≤ VREG – 1.2 V
1000
−40°C ≤ TJ ≤ 125°C,
1 V ≤ VOUT ≤ VREG – 1.3 V
700
6
1000
1000
V/V
TJ = 25°C
3500
3500
1
–40°C ≤ TJ ≤ 125°C
1.2
1.3
TJ = 25°C
1
–40°C ≤ TJ ≤ 125°C
1.2
V
1.3
TJ = 25°C
0.1
0.5
0.1
0.5
–40°C ≤ TJ ≤ 125°C
1
TJ = 25°C
–40°C ≤ TJ ≤ 125°C
μA
1
LM3411A 5-V
70
94
118
LM3411 5-V
70
94
118
IOUT = 1 mA, 10 Hz ≤ f ≤ 10 kHz
80
kΩ
μVRMS
Limits are 100% production tested at 25°C. Limits over the operating temperature range are ensured through correlation using Statistical
Quality Control (SQC) methods. The limits are used to calculate TIs Averaging Outgoing Level (AOQL).
Typical numbers are at 25°C and represent the most likely parametric norm.
Actual test is done using equivalent current sink instead of a resistor load.
VSAT = VIN – VOUT, when the voltage at the IN pin is forced 100 mV above the nominal regulating voltage (VREG).
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6.7 Typical Characteristics
Figure 1. Normalized Temperature Drift
Figure 2. Quiescent Current
Figure 3. Output Saturation Voltage, VSAT
Figure 4. Bode Plot
Figure 5. Bode Plot
Figure 6. Bode Plot
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Typical Characteristics (continued)
8
Figure 7. Response Time for 3.3-V Version (CC = 0 pF)
Figure 8. Response Time for 3.3-V Version (CC = 10 nF)
Figure 9. Response Time for 5-V Version (CC = 0 pF)
Figure 10. Response Time for 5-V Version (CC = 10 nF)
Figure 11. Tempco of Internal Feedback Resistor (Rf)
Figure 12. Regulation Voltage Change vs Output Current
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Typical Characteristics (continued)
Figure 13. Regulation Voltage vs Output Voltage
and Load Resistance
Figure 14. Regulation Voltage vs Output Voltage
and Load Resistance
7 Parameter Measurement Information
Figure 15. Circuit Used for Bode Plots
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Parameter Measurement Information (continued)
Figure 16. Circuit Used for Response Time
10
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8 Detailed Description
8.1 Overview
The LM3411 is a shunt regulator specifically designed to be the reference and control section in an overall
feedback loop of a regulated power supply. The regulated output voltage is sensed between the IN pin and
GROUND pin of the LM3411. If the voltage at the IN pin is less than the LM3411 regulating voltage (VREG), the
OUT pin sources no current. As the voltage at the IN pin approaches the VREG voltage, the OUT pin begins
sourcing current. This current is then used to drive a feedback device, (optocoupler) or a power device (linear
regulator, switching regulator, and so forth) which serves the output voltage to be the same value as VREG.
In some applications (even under normal operating conditions), the voltage on the IN pin can be forced above
the VREG voltage. In these instances, the maximum voltage applied to the IN pin should not exceed 20 V. In
addition, an external resistor may be required on the OUT pin to limit the maximum current to 20 mA.
8.2 Functional Block Diagrams
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Figure 17. LM3411 Functional Diagram
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Functional Block Diagrams (continued)
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Figure 18. Detailed Schematic
8.3 Feature Description
The LM3411 devices contain an internal operational amplifier, precision reference, feedback resister divider, and
a bi-polar transistor suitable for driving an optocoupler. The divider resistor is sized such that the system will
regulate the +IN pin to either 3.3 V or 5 V depending on the device version used. By connecting a feedback
network from the OUT pin to the COMP pin, local compensation is implemented to stabilize the system.
8.4 Device Functional Modes
The primary mode of operation for the LM3411 is as a shunt regulator. In addition the device has robust
overcurrent protection. These features make it applicable to a wide range of applications ranging from isolated
feedback control to traditional shunt regulation.
12
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9 Application 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.
9.1 Application Information
The LM3411 is a high-efficiency shunt regulator optimized for driving an opto-coupler in an isolated feedback
system. This enables accurate regulation of the output voltage as well as convenient drive to the opto-coupler in
a small SOT-23 package. In addition to isolated feedback systems the LM3411 is also applicable to a wide
variety of linear regulator applications.
9.2 Typical Applications
9.2.1 LM3411 Typical Application
Figure 19 shows a typical use case for the LM3411. Here, the device is used as a precision shunt regulator to
control the output voltage of a switching power supply. The LM3411 provides the functionality necessary to drive
the external opto-coupler, an on-board reference necessary for precision control of the DC output voltage, and an
on-board operational amplifier for providing the necessary compensation to optimize the transient performance of
the system.
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Figure 19. LM3411 Typical Application Schematic
9.2.1.1 Design Requirements
The following sections provide a variety of application level design examples. See the following for the basic
requirements.
● Isolated flyback converter example is 5 V with 250 mA.
● Isolated flyback converter example is 3.3 V or 5 V with 1.5 A.
● Buck converter example is 5 V with 1 A.
● Flyback converter example is VIN = –20 V to –10 V and VOUT = –5 V with 1 A.
● Low dropout linear regulator example is 5 V with 1 A.
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Typical Applications (continued)
● Low dropout linear regulator example is 3.3 V and 0.5 A.
● Precision positive voltage regulator with accurate current limit is VIN = 9 V to 20 V and VOUT = 5 V.
● Negative voltage regulator example is VIN = –8 V to –20 V and VOUT = –5 V.
● 250-mA shunt regulator example is VOUT = 5 V.
9.2.1.2 Detailed Design Procedure
9.2.1.2.1 Compensation
The inverting input of the error amplifier is brought out to allow overall closed-loop compensation. In many of the
applications circuits shown in the subsequent sections, compensation is provided by a single capacitor
connected from the compensation pin to the out pin of the LM3411. The capacitor values shown in the
schematics accompanying these sections are adequate under most conditions, but they can be increased or
decreased depending on the desired loop response. Applying a load pulse to the output of a regulator circuit and
observing the resultant output voltage response is a easy method of determining the stability of the control loop.
Analyzing more complex feedback loops requires additional information.
The formula for AC gain at a frequency (f) as in Equation 1.
Gain (f ) 1
where Z f (f )
Z f (f )
Rf
1
j u 2S u f u C
where
•
•
Rf ≈ 52 kΩ for the 3.3-V part
Rf ≈ 94 kΩ for the 5-V part
(1)
The resistor (Rf) in the formula is an internal resistor located on the die. Since this resistor value will affect the
phase margin, the worst case maximum and minimum values are important when analyzing closed loop stability.
The minimum and maximum room temperature values of this resistor are specified in Electrical Characteristics:
3.3-V Version of this data sheet, and Figure 11 shows the temperature coefficient from Typical Characteristics. In
the applications shown in the subsequent sections, the worst case phase margin occurs with minimum values of
Rf.
9.2.1.2.2 Test Circuit
The test circuit shown in Figure 20 can be used to measure and verify various LM3411 parameters. Test
conditions are set by forcing the appropriate voltage at the VOUT Set test point and selecting the appropriate RL
or IOUT as specified in Electrical Characteristics. Use a DVM at the measure test points to read the data.
14
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Typical Applications (continued)
Figure 20. LM3411 Test Circuit
9.2.1.3 Application Curves
Figure 21. Regulation Voltage vs Output Voltage
and Load Resistance
Figure 22. Regulation Voltage vs Output Voltage
and Load Resistance
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Typical Applications (continued)
9.2.2 Isolated 250-mA Flyback Switching Regulator
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Figure 23. Isolated 250-mA Flyback Switching Regulator Schematic
9.2.2.1 Design Requirements
The design requirements for this isolated flyback converter example are 5 V with 250 mA.
9.2.2.2 Detailed Design Procedure
The LM3411 regulator or driver provides the reference and feedback drive functions in a regulated power supply.
It can also be used together with many different types of regulators, (both linear and switching) as well as other
power semiconductor devices to add precision and improve regulation specifications. Output voltage tolerances
better than 0.5% are possible without using trim pots or precision resistors.
One of the main applications of the LM3411 is to drive an opto-isolator to provide feedback signal isolation in a
switching regulator circuit. For low current applications (up to 250 mA), see Figure 23 for a circuit that provides
good regulation and complete input and output electrical isolation.
For an input voltage of 15 V, this circuit can provide an output of either 3.3 V or 5 V with a load current up to
250 mA with excellent regulation characteristics. With the part values shown, this circuit operates at 80 kHz, and
can be synchronized to a clock or an additional LM3578. See LM3578A's data sheet (SNVS767) for additional
information.
16
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Typical Applications (continued)
9.2.3 Isolated 1.5-A Flyback Switching Regulator
Copyright © 2016, Texas Instruments Incorporated
Figure 24. Isolated 1.5-A Flyback Switching Regulator Using a LM2577
9.2.3.1 Design Requirements
The design requirements for this isolated flyback converter example are 3.3 V or 5 V with 1.5 A.
9.2.3.2 Detailed Design Procedure
An isolated DC-DC flyback converter capable of higher output current is shown in Figure 24. This circuit uses the
LM2577 SIMPLE SWITCHER voltage regulator for the Pulse Width Modulation (PWM), power switch, and
protection functions, while the LM3411 provides the voltage reference, gain, and opto-coupler drive functions. In
this circuit, the reference and error amplifier in the LM2577 are not used (note that the feedback pin is grounded).
The gain is provided by the LM3411. Since the voltage reference is located on the secondary side of the
transformer, this circuit provides very good regulation specifications.
The output of a switching regulator typically will contain a small ripple voltage at the switching frequency and may
also contain voltage transients. These transient voltage spikes can be sensed by the LM3411 and could give an
incorrect regulation voltage. An RC filter consisting of a 1-Ω resistor and a 100-nF capacitor will filter these
transients and minimize this problem. The 1-Ω resistor should be located on the ground side of the LM3411, and
the capacitor should be physically located near the package.
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Typical Applications (continued)
9.2.4 Precision 1-A Buck Regulator
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Figure 25. Precision 1-A Buck Regulator Schematic
9.2.4.1 Design Requirements
The design requirements for this precision buck converter example are 5 V with 1 A.
9.2.4.2 Detailed Design Procedure
Improved output voltage tolerance and regulation specifications are possible by combining the LM3411A with one
of the SIMPLE SWITCHER buck regulator IC's, such as the LM2574, LM2575, or LM2576. Figure 25 shows a
circuit capable of providing a 5-V, ±0.5% output (1% over the operating temperature range) without using any
trim-pots or precision resistors. Typical line regulation numbers are a 1 mV change on the output for a 8 V to
18 V change on the input, and load regulation of 1 mV with a load change from 100 mA to 1 A.
9.2.5 Negative Input, Negative or Positive Output Flyback Regulator
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Figure 26. Negative Input, Negative or Positive Output Flyback Regulator Schematic
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Typical Applications (continued)
9.2.5.1 Design Requirements
The design requirements for this flyback converter example are VIN = –20 V to –10 V and VOUT = –5 V with 1 A.
9.2.5.2 Detailed Design Procedure
A DC-DC flyback converter that accepts a negative input voltage, and delivers either a positive or negative output
is shown in Figure 26. The circuit uses a buck regulator (such as the LM2574, LM2575, or LM2576, depending
on how much output current is needed) operating in a flyback configuration. The LM3411 provides the reference
and the required level shifting circuitry needed to make the circuit work correctly.
A unique feature of this circuit is the ability to ground either the high or low side of the output, thus generating
either a negative or a positive output voltage. Although no isolation is provided, with the addition of an optoisolator and related components, this circuit could provide input/output isolation.
Combining a LM3411A 5-V version with a 1-A low dropout linear regulator results in a 5 V ±0.5% (1% over the
operating temperature range) regulator with excellent regulation specifications, with no trimming or 1% resistors
needed.
An added benefit of this circuit (and also true of many of the other circuits shown) is the high-side and low-side
remote output voltage sensing feature. Sensing the output voltage at the load eliminates the voltage drops
associated with wire resistance, thus providing near perfect load regulation.
9.2.6 Precision 5-V, 1-A Low Dropout Regulator
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Figure 27. Precision 5-V, 1-A Low Dropout Regulator
9.2.6.1 Design Requirements
The design requirements for this precision low dropout linear regulator example are 5 V with 1 A.
9.2.6.2 Detailed Design Procedure
Figure 27 shows a 5-V, 1-A regulator circuit featuring low dropout, very good regulation specifications, selfprotection features, and allows output voltage sensing. The regulator used is a LM2941 adjustable low dropout
positive regulator, which also features an ON/OFF pin to provide a shutdown feature.
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Typical Applications (continued)
9.2.7 3.3-V, 0.5-A Low Dropout Regulator
Copyright © 2016, Texas Instruments Incorporated
Figure 28. 3.3-V, 0.5-A Low Dropout Regulator Schematic
9.2.7.1 Design Requirements
The design requirements for this low dropout linear regulator example are 3.3 V and 0.5 A.
9.2.7.2 Detailed Design Procedure
The circuit in Figure 28 shows a 3.3-V low dropout regulator using the LM3411-3.3 and several discrete
components. This circuit is capable of excellent performance with both the dropout voltage and the ground pin
current specifications improved over the LM2941 and LM3411 circuit.
9.2.8 Precision Positive Voltage Regulator With Accurate Current Limit
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Figure 29. Precision Positive Voltage Regulator With Accurate Current Limit Schematic
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Typical Applications (continued)
9.2.8.1 Design Requirements
The design requirements for this precision positive voltage regulator with accurate current limit are VIN = 9 V to
20 V and VOUT = 5 V.
9.2.8.2 Detailed Design Procedure
The standard LM317 three terminal adjustable regulator circuit can greatly benefit by adding a LM3411.
Performance is increased and features are added. Figure 29 shows a circuit capable of providing further
improved line and load regulation, lower temperature drift, and full remote output voltage sensing on both the
high and low side. In addition, a precise current limit or constant current feature is simple to add.
Current limit protection in most IC regulators is mainly to protect the IC from gross overcurrent conditions which
could otherwise fuse bonding wires or blow IC metalization, therefore not much precision is needed for the actual
current limit values. Current limit tolerances can sometimes vary from ±10% to as high as +300% over
manufacturing and temperature variations. Often critical circuitry requires a much tighter control over the amount
of current the power supply can deliver. For example, a power supply may be needed that can deliver 100% of
its design current, but can still limit the maximum current to 110% to protect critical circuitry from high current
fault conditions.
The circuit in Figure 29 can provide a current limit accuracy that is better than ±4%, over all possible variations,
in addition to having excellent line, load, and temperature specifications.
9.2.9 Precision Negative Voltage Regulator
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Figure 30. Precision Negative Voltage Regulator Schematic
Copyright © 2016, Texas Instruments Incorporated
Figure 31. Precision Negative Voltage Regulator With Accurate Current Limit
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Typical Applications (continued)
9.2.9.1 Design Requirements
The design requirements for this negative voltage regulator example are VIN = –8 V to –20 V and VOUT = –5 V.
9.2.9.2 Detailed Design Procedure
Like the positive regulators, the performance of negative adjustable regulators can also be improved by adding
the LM3411. Output voltages of either 3.3 V or 5 V at currents up to 1.5 A (3 A when using a LM333) are
possible. Adding two resistors to the circuit in Figure 30 adds the precision current limit feature as shown in
Figure 31. Current limit tolerances of ±4% over manufacturing and temperature variations are possible with this
circuit.
9.2.10 4.7-V Power ON Detector With Hysteresis
Copyright © 2016, Texas Instruments Incorporated
Figure 32. 4.7-V Power ON Detector With Hysteresis Schematic
9.2.10.1 Detailed Design Procedure
Figure 32 shows a simple 5-V supply monitor circuit. Using the LM3411's voltage reference, operational amplifier
(as a comparator) and output driver, this circuit provides a LED indication of the presence of the 5-V supply.
9.2.11 ±50-mV External Trim
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Figure 33. ±50-mV External Trim Schematic
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Typical Applications (continued)
9.2.11.1 Detailed Design Procedure
The LM3411 initial room temperature tolerance is ±1% and ±0.5% for the A grade part. If a tighter tolerance is
needed, see Figure 33 for a trim scheme that provides approximately ±1% adjustment range of the regulation
voltage (VREG).
9.2.12 250-mA Shunt Regulator
Copyright © 2016, Texas Instruments Incorporated
Figure 34. 250-mA Shunt Regulator Schematic
9.2.12.1 Design Requirements
The design requirement for this 250-mA shunt regulator example is VOUT = 5 V.
9.2.12.2 Detailed Design Procedure
The LM3411 is ensured to drive a 15 mA load, but if more current is needed, a NPN boost transistor can be
added. Figure 34 shows a shunt regulator capable of providing excellent regulation over a very wide range of
current.
9.2.13 Voltage Detector
Copyright © 2016, Texas Instruments Incorporated
Figure 35. Voltage Detector Schematic
9.2.13.1 Detailed Design Procedure
Perhaps one of the simplest applications for the LM3411 is the voltage detector circuit shown in Figure 35. The
OUT pin is low when the input voltage is less than VREG. When the VIN pin rises above VREG, the OUT pin is
pulled high by the internal NPN output resistor.
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Typical Applications (continued)
9.2.14 Overvoltage Crowbar
Copyright © 2016, Texas Instruments Incorporated
Figure 36. Overvoltage Crowbar Schematic
9.2.14.1 Detailed Design Procedure
Also an overvoltage detector, the crowbar circuit shown in Figure 36 is normally located at the output of a power
supply to protect the load from an overvoltage condition should the power supply fail with an input/output short.
10 Power Supply Recommendations
The output of a switching regulator typically will contain a small ripple voltage at the switching frequency and may
also contain voltage transients. These transient voltage spikes can be sensed by the LM3411 and could give an
incorrect regulation voltage. An RC filter consisting of a 1-Ω resistor and a 100-nF capacitor will filter these
transients and minimize this problem.
11 Layout
11.1 Layout Guidelines
The 1-Ω resistor should be located on the ground side of the LM3411, and the 100-nF capacitor should be
physically located near the package.
11.2 Layout Example
OUT 5
2 GND
3
200 Q
Connect to
ground plane
1 +IN
100 nF
100 nF
Connect to
Output
COMP 4
Connect to
Optocoupler
Figure 37. LM3411 Layout Schematic
24
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
For related documentation see the following:
• AN-450 Surface Mounting Methods and Their Effect on Product Reliability, SNOA742
• AN-1095 Design of Isolated Converters Using Simple Switchers, SNVA005
• AN-1305 LM5030 Evaluation Board, SNVA078
• Versatility of the LM5030 PWM Push-Pull Controller, SNVA548
• LM2578A/LM3578A Switching Regulator, SNVS767
12.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.3 Trademarks
E2E is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
12.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
12.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM3411AM5-3.3/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
D00A
LM3411AM5-5.0/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
D01A
LM3411AM5X-5.0/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
D01A
LM3411M5-3.3/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
D00B
LM3411M5-5.0/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
D01B
LM3411M5X-3.3/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
D00B
LM3411M5X-5.0/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
D01B
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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