Datasheet LM3411AM5-5.0, LM3411AM5-3.3, LM3411M5X-5.0, LM3411M5X-3.3, LM3411AM5X-5.0 Datasheet (NSC)

LM3411
Precision Secondary Regulator/Driver

General Description

The LM3411isalowpowerfixed-voltage(3.3Vor5.0V)pre­cision shunt regulator designed specifically fordrivinganop­toisolator to provide feedback isolation in a switching regula­tor.

The LM3411 circuitry includes an internally compensated op
amp, a bandgap reference, NPN output transistor, and volt­age setting resistors.

A trimmed precision bandgap reference with temperature
drift curvature correction, provides a guaranteed 1%preci­sion over theoperatingtemperature range (A grade version).
The amplifier’s inverting input 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 sub-miniature 5-lead SOT23-5 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.

Features

n Fixed voltages of 3.3V and 5.0V with initial tolerance of

±

1%for standard grade and±0.5%for A grade

n Custom voltages available (3V–17V)
n Wide output current range, 20 µA–15 mA
n Low temperature coefficient
n Available in 5-lead SOT23-5 surface mount package

(tape and reel)

Applications

n Secondary controller for isolated DC/DC PWM switching

regulators systems

n Use with LDO regulator for high-precision fixed output

regulators

n Precision monitoring applications
n Use with many types of regulators to increase precision

and improve performance

LM3411 Precision Secondary Regulator/Driver

December 1999

Typical Application and Functional Diagram

DS011987-1

Basic Isolated DC/DC Converter

DS011987-2

LM3411 Functional Diagram

SIMPLE SWITCHER™is a tradmark of National Semiconductor Corporation.

© 1999 National Semiconductor Corporation DS011987 www.national.com

Connection Diagrams and Order Information

LM3411

5-Lead Small Outline Package (M5)

Actual Size

DS011987-4

Top View

DS011987-3

For Ordering Information

See

Figure 1

See NS Package Number MA05B

in this Data Sheet

*No internal connection, but should be soldered to PC board for best heat
transfer.

Five Lead Surface Mount Package Marking
and Order Information (SOT23-5)

The small SOT23-5 package allows only 4 alphanumeric characters to identify the product. The table below contains the field in­formation marked on the package.

Grade

3.3V A (Prime) LM3411AM5-3.3 D00A 1000 unit increments on tape and reel

3.3V A (Prime) LM3411AM5X-3.3 D00A 3000 unit increments on tape and reel

3.3V B (Standard) LM3411M5-3.3 D00B 1000 unit increments on tape and reel

3.3V B (Standard) LM3411M5X-3.3 D00B 3000 unit increments on tape and reel

5.0V A (Prime) LM3411AM5-5.0 D01A 1000 unit increments on tape and reel

5.0V A (Prime) LM3411AM5X-5.0 D01A 3000 unit increments on tape and reel

5.0V B (Standard) LM3411M5-5.0 D01B 1000 unit increments on tape and reel

5.0V B (Standard) LM3411M5X-5.0 D01B 3000 unit increments on tape and reel

The first letter “D” identifies the part as a Driver, the next two numbers indicate the voltage, “00” for 3.3V part and “01” for a 5V
part. The fourth letter indicates the grade, “B” for standard grade, “A” for the prime grade.

The SOT23-5 surface mount package is only available on tape in quantities increments of 250 on tape and reel (indicated by the
letters “M5” in the part number), or in quantities increments of 3000 on tape and reel (indicated by the letters “M5X” in the part
number).

Order Information Package

Marking

FIGURE 1. SOT23-5 Marking and Order Information

Supplied as

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Input Voltage V(IN) 20V
Output Current 20 mA
Junction Temperature 150˚C
Storage Temperature −65˚C to +150˚C
Lead Temperature

Vapor Phase (60 sec.) +215˚C
Infrared (15 sec.) +220˚C

Power Dissipation (T

2) 300 mW

=

25˚C) (Note

A

ESD Susceptibility (Note 3)

Human Body Model 1500V

See AN-450 “Surface Mounting Methods and Their Effect on
Product Reliability” for methods on soldering surface-mount
devices.

Operating Ratings (Notes 1, 2)

Ambient Temperature Range −40˚C ≤ T
Junction Temperature Range −40˚C ≤ T
Output Current 15 mA

≤ +85˚C

A

≤ +125˚C

J

LM3411

LM3411-3.3 Electrical Characteristics

Specifications with standard type face are for T

ture Range. Unless otherwise specified, V(IN)=V

Symbol Parameter Conditions Typical LM3411A-3.3 LM3411-3.3 Units

V

REG

Regulation Voltage I

Regulation Voltage I

OUT

OUT

Tolerance

I

q

G

m

Quiescent Current I

OUT

Transconductance 20 µA ≤ I
∆I

/∆V

OUT

REG

1mA≤I

A

V

Voltage Gain 1V ≤ V
∆V

OUT

/∆V

REG

=

R

L

1V ≤ V

=

R

V

SAT

Output Saturation V(IN)=V
(Note 7) I

I

L

Output Leakage V(IN)=V
Current V

R

f

Internal Feedback 52 kΩ

L

OUT

OUT

Resistor (Note 8) 65 65 kΩ(max)

E

n

Output Noise I

OUT

Voltage

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

REG,VOUT

=

1.5V.

(Note 4) Limit Limit (Limits)

(Note 5) (Note 5)

=

5 mA 3.3 V

3.317/3.333 3.333/3.366 V(max)

3.284/3.267 3.267/3.234 V(min)

=

5mA

=

5mA 85 µA

±

0.5/±1

±1/±

2

%

(max)

110/115 125/150 µA(max)

≤ 1 mA 3.3 mA/mV

OUT

1.5/0.75 1/0.50 mA/mV(min)

≤ 15 mA 6.0 mA/mV

OUT

3.3/2.0 2.5/1.7 mA/mV(min)

≤ V

OUT

− 1.2V (−1.3) 1000 V/V

REG

140Ω (Note 6) 550/250 450/200 V/V(min)

≤ V

OUT

− 1.2V (−1.3) 3500 V/V

REG

2kΩ 1500/900 1000/700 V/V(min)

+100 mV 1.0 V

REG

=

15 mA 1.2/1.3 1.2/1.3 V(max)

−100 mV 0.1 µA

REG

=

0V 0.5/1.0 0.5/1.0 µA(max)

39 39 kΩ(min)

=

1 mA, 10 Hz ≤ f ≤ 10 kHz 50 µV

RMS

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LM3411-5.0 Electrical Characteristics

Specifications with standard type face are for T

LM3411

ture Range. Unless otherwise specified, V(IN)=V

Symbol Parameter Conditions Typical LM3411A-5.0 LM3411-5.0 Units

V

Regulation Voltage I

REG

Regulation Voltage I

OUT

OUT

Tolerance

I

q

G

m

Quiescent Current I

OUT

Transconductance 20 µA ≤ I
∆I

/∆V

OUT

REG

1mA≤I

A

V

Voltage Gain 1V ≤ V
∆V

OUT

/∆V

REG

=

R

L

1V ≤ V

=

R

V

SAT

Output Saturation V(IN)=V
(Note 7) I

I

L

Output Leakage V(IN)=V
Current V

R

f

Internal Feedback 94 kΩ

L

OUT

OUT

Resistor (Note 8) 118 118 kΩ(max)

E

n

Output Noise I

OUT

Voltage

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is in­tended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The
guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed
test conditions.

Note 2: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
bient thermal resistance), and T
given in the Absolute Maximum Ratings, whichever is lower. The typical thermal resistance (θ
for the M5 package.

Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 4: Typical numbers are at 25˚C and represent the most likely parametric norm.
Note 5: Limits are 100%production tested at 25˚C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control

(SQC) methods. The limits are used to calculate National’s Averaging Outgoing Level (AOQL).

Note 6: Actual test is done using equivalent current sink instead of a resistor load.
Note 7: V
Note 8: See Applications and Curves sections for information on this resistor.

SAT

=

V(IN) − V

(ambient temperature). The maximum allowable power dissipation at any temperature is (P

A

, when the voltage at the IN pin is forced 100 mV above the nominal regulating voltage (V

OUT

=

25˚C, and those with boldface type apply over full Operating Tempera-

J

REG,VOUT

=

1.5V.

(Note 4) Limit Limit (Limits)

(Note 5) (Note 5)

=

5mA 5 V

5.025/5.050 5.050/5.100 V(max)

4.975/4.950 4.950/4.900 V(min)

=

5mA

=

5mA 85 µA

±

0.5/±1

±1/±

2

110/115 125/150 µA(max)

≤ 1 mA 3.3 mA/mV

OUT

1.5/0.75 1.0/0.5 mA/mV(min)

≤ 15 mA 6.0 mA/mV

OUT

3.3/2.0 2.5/1.7 mA/mV(min)

≤ V

OUT

− 1.2V (−1.3) 1000 V/V

REG

250Ω (Note 6) 750/350 650/300 V/V(min)

≤ V

OUT

− 1.2V (−1.3) 3500 V/V

REG

2kΩ 1500/900 1000/700 V/V(min)

+100 mV 1.0 V

REG

=

15 mA 1.2/1.3 1.2/1.3 V(max)

−100 mV 0.1 µA

REG

=

0V 0.5/1.0 0.5/1.0 µA(max)

70 70 kΩ(min)

=

1 mA, 10 Hz ≤ f ≤ 10 kHz 80 µV

(maximum junction temperature), θJA(junction to am-

Jmax

) when soldered to a printed circuit board is approximately 306˚C/W

JA

REG

Dmax

).

=

T

Jmax−TA

)/θJAor the number

%

(max)

RMS

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Typical Performance Characteristics

LM3411

Normalized
Temperature Drift

Circuit Used for Bode Plots

Bold Plot

DS011987-30

DS011987-8

Quiescent Current

Bode Plot

Response Time
for 3.3V Version

=

(C

0 pF)

C

DS011987-31

DS011987-33

Output Saturation
Voltage (V)

SAT

Bode Plot

Response Time
for 3.3V Version

=

(C

10 nF)

C

DS011987-32

DS011987-34

DS011987-44

Circuit Used for Response Time

DS011987-11

Response Time
for 5V Version

=

(C

0 pF)

C

DS011987-35

DS011987-37

Response Time
for 5V Version

=

(C

10 nF)

C

DS011987-36

DS011987-38

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Typical Performance Characteristics (Continued)

LM3411

Tempco of Internal
Feedback Resistor (Rf)

Regulation Voltage
Change vs
Output Current

Regulation Voltage vs
Output Voltage and
Load Resistance

Regulation Voltage vs
Output Voltage and
Load Resistance

DS011987-39

DS011987-42

DS011987-40

DS011987-41

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Product Description

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 (V
age at the IN pin approaches the V
begins sourcing current. This current is then used to drive a

), the OUT pin sources no current. As the volt-

REG

voltage, the OUT pin

REG

feedback device, (opto-coupler) or a power device, (linear
regulator, switching regulator, etc.) which servos the output
voltage to be the same value as V

REG

.

In some applications, (even under normal operating condi­tions) the voltage on the IN pin can be forced above the
V

voltage. In these instances, the maximum voltage ap-

REG

plied to the IN pin should not exceed 20V.In addition, an ex­ternal resistor may be required on the OUT pin to limit the
maximum current to 20 mA.

Compensation

The inverting input of the error amplifier is brought out to al­low overall closed-loop compensation. In many of the appli­cations circuits shown here, 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 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) is as follows;

where Rf≈ 52 kΩ for the 3.3V part, and Rf≈ 94 kΩ for the 5V
part.

The resistor (R
on the die. Since this resistor value will affect the phase mar-

) in the formula is an internal resistor located

f

gin, 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 the Electrical Characteristics section of this data
sheet, and a curve showing the temperature coefficient is
shown in the curves section. In the applications shown here,
the worst case phase margin occurs with minimum values of
R

.

f

Test Circuit

The test circuit shown in
and verify various LM3411 parameters. Test conditions are
set by forcing the appropriate voltage at the V
point and selecting the appropriate R
the Electrical Characteristics section. Use a DVM at the
“measure” test points to read the data.

Figure 2

can be used to measure

or I

L

OUT

as specified in

OUT

Set test

LM3411

FIGURE 2. LM3411 Test Circuit

DS011987-14

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Applications Information

LM3411

DS011987-15

FIGURE 3. Isolated 250 mA Flyback Switching Regulator

FIGURE 4. Isolated 1.5A Flyback Switching Regulator Using a LM2577

The LM3411 regulator/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) the circuit shown in

Figure 3

provides good regulation

and complete input/output electrical isolation.
For an input voltage of 15V,this circuit can provide an output

of either 3.3V or 5V 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 LM1578 data
sheet for additional information.)

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DS011987-16

An isolated DC/DC flyback converter capable of higher out­put current is shown in
LM2577 SIMPLE SWITCHER

Figure 4

. This circuit utilizes the

™

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 1Ω resistor
and a 100 nF capacitor will filter these transients and mini­mize this problem. The 1Ω resistor should be located on the
ground side of the LM3411, and the capacitor should be
physically located near the package.

Applications Information (Continued)

FIGURE 5. Precision 1A Buck Regulator

LM3411

DS011987-17

FIGURE 6. Negative Input, Negative or Positive Output Flyback Regulator

Improved output voltage tolerance and regulation specifica­tions are possible by combining the LM3411Awithone of the
SIMPLE SWITCHER buck regulator IC’s, such as the
LM2574, LM2575, or LM2576. The circuit shown in
can provide a 5V,±0.5%Output (1%over the operating tem­perature range) without using any trim-pots or precision re­sistors. Typical line regulation numbers area1mVchange
on the output for a 8V–18V change on the input, and load
regulation of 1 mV with a load change from 100 mA–1A.

A DC-DC flyback converter that accepts a negative input
voltage, and delivers either a positive or negative output is
shown in

Figure 6

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

. The circuit utilizes a buck regulator (such

Figure 5

DS011987-18

provided, with the addition of an opto-isolator and related
components, this circuit could provide input/output isolation.

Combining a LM3411A-5.0with a 1A low dropout linear regu­lator results in a 5V
ture 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 here) 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.

A 5V, 1A regulator circuit featuring low dropout, very good
regulation specifications, self protection features and allows
output voltage sensing is shown in
used is a LM2941 adjustable low dropout positive regulator,
which also features an ON/OFF pin to provide a shutdown
feature.

±

0.5%(1%over the operating tempera-

Figure 7

. The regulator

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Applications Information (Continued)

LM3411

FIGURE 7. Precision 5V 1A Low Dropout Regulator

FIGURE 8. 3.3V 0.5A Low Dropout Regulator

Figure 8

The circuit in
using the LM3411-3.3 and several discrete components.

shows a 3.3V low dropout regulator

DS011987-20

DS011987-19

This circuit is capable of excellent performance with both the
dropout voltage and the ground pin current specifications im­proved over the LM2941/LM3411 circuit.

The standard LM317 three terminal adjustable regulator cir­cuit can greatly benefit by adding a LM3411. Performance is
increased and features are added. The circuit shown in

ure 9

provides much improved line and load regulation,

Fig-

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 over-current 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
that is better than

Figure 9

can provide a current limit accuracy

±

4%, over all possible variations, in addi­tion to having excellent line, load and temperature
specifications.

FIGURE 9. Precision Positive Voltage Regulator with Accurate Current Limit

Like the positive regulators, the performance of negative ad­justable regulators can also be improved by adding the
LM3411. Output voltages of either 3.3V or 5V at currents up
to 1.5A (3A when using a LM333) are possible. Adding two

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DS011987-21

resistors to the circuit in

Figure 10

limit feature as shown in

±

of

4%over manufacturing and temperature variations are

adds the precision current

Figure 11

. Current limit tolerances

possible with this circuit.

Applications Information (Continued)

DS011987-22

FIGURE 10. Precision Negative Voltage Regulator

DS011987-23

FIGURE 11. Precision Negative Voltage

Regulator with Accurate Current Limit

Figure 12

Asimple 5V supply monitor circuit is shown in
ing the LM3411’s voltage reference, op-amp (as a compara­tor) and output driver,this circuit provides a LED indication of
the presence of the 5V supply.

. Us-

DS011987-25

FIGURE 13.±50 mV External Trim

The LM3411 is guaranteed to drive a 15 mA load, but if more
current is needed, a NPN boost transistor can be added. The
circuit shown in

Figure 14

is a shunt regulator capable of pro-

viding excellent regulation over a very wide range of current.

DS011987-26

FIGURE 14. 250 mA Shunt Regulator

Perhaps one of the simplest applications for the LM3411 is
the voltage detector circuit shown in

Figure 15

is low when the input voltage is less than V
V(IN) pin rises above V
internal NPN output resistor.

, the OUT pin is pulled high by the

REG

. The OUT pin

. When the

REG

LM3411

DS011987-24

FIGURE 12. 4.7V Power ON Detector with Hysteresis

±

The LM3411 initial room temperature tolerance is

±

0.5%for the “A” grade part. If a tighter tolerance is needed,

a trim scheme is shown in

±

mately

1%adjustment range of the regulation voltage

(V

).

REG

Figure 13

that provides approxi-

1%and

DS011987-27

FIGURE 15. Voltage Detector

Also an overvoltage detector, the crowbar circuit shown in

Figure 16

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.

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Applications Information (Continued)

LM3411

Schematic Diagram

DS011987-28

FIGURE 16. Overvoltage Crowbar

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DS011987-29

Physical Dimensions inches (millimeters) unless otherwise noted

LM3411 Precision Secondary Regulator/Driver

5-Lead Small Outline Package (M5)

Order Number LM3411M5-3.3, LM3411AM5-3.3,

LM3411M5-5.0 or LM3411AM5-5.0

NS Package Number MA05B

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