National Semiconductor LM2594, LM2594HV Technical data

LM2594/LM2594HV
SIMPLE SWITCHER

®

Power Converter 150 kHz 0.5A

Step-Down Voltage Regulator

General Description

The LM2594/LM2594HV series of regulators are monolithic
integrated circuits that provide all the active functions for a
step-down (buck) switching regulator, capable of driving a

0.5A load with excellent line and load regulation. These de­vices are available in fixed output voltages of 3.3V, 5V, 12V,
and an adjustable output version, and are packaged in a
8-lead DIP and a 8-lead surface mount package.

Requiring a minimum number of external components, these
regulators are simple to use and feature internal frequency
compensation
line and load regulation specifications.

The LM2594/LM2594HV series operates at a switching fre­quency of 150 kHz thus allowing smaller sized filter compo­nents than what would be needed with lower frequency
switching regulators. Because of its high efficiency, the cop­per traces on the printed circuit board are normally the only
heat sinking needed.

A standard series of inductors (both through hole and sur­face mount types) are available from several different manu­facturers optimized for use with the LM2594/LM2594HV se­ries. This feature greatly simplifies the design of
switch-mode power supplies.

Other features include a guaranteed
put voltage under all conditions of input voltage and output
load conditions, and
ternal shutdown is included, featuring typically 85 µA
standby current. Self protection features include a two stage
frequency reducing current limit for the output switch and an
over temperature shutdown for complete protection under
fault conditions.

†

, a fixed-frequency oscillator, and improved

±

4%tolerance on out-

±

15%on the oscillator frequency. Ex-

December 1999

The LM2594HV is for applications requiring an input voltage
up to 60V.

Features

n 3.3V, 5V, 12V, and adjustable output versions
n Adjustable version output voltage range, 1.2V to 37V

(57V for the HV version)
conditions

n Available in 8-pin surface mount and DIP-8 package
n Guaranteed 0.5A output current
n Input voltage range up to 60V
n Requires only 4 external components
n 150 kHz fixed frequency internal oscillator
n TTL Shutdown capability
n Low power standby mode, I
n High Efficiency
n Uses readily available standard inductors
n Thermal shutdown and current limit protection

±

4%max over line and load

typically 85 µA

Q

Applications

n Simple high-efficiency step-down (buck) regulator
n Efficient pre-regulator for linear regulators
n On-card switching regulators
n Positive to Negative convertor

LM2594/LM2594HV SIMPLE SWITCHER Power Converter 150 kHz 0.5A Step-Down Voltage

Regulator

Typical Application (Fixed Output Voltage Versions)

DS012439-1

SIMPLE SWITCHER and

© 1999 National Semiconductor Corporation DS012439 www.national.com

Switchers Made Simple

™

are registered trademarks of National Semiconductor Corporation.

Connection Diagrams and Order Information

8-Lead DIP (N)

LM2594/LM2594HV

DS012439-2

Top View

Order Number

LM2594N-3.3, LM2594N-5.0,

LM2594N-12 or LM2594N-ADJ

LM2594HVN-3.3, LM2594HVN-5.0,

LM2594HVN-12 or LM2594HVN-ADJ

See NS Package Number N08E

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

‡

Patent Number 5,382,918.

8-Lead Surface Mount (M)

DS012439-3

Top View

Order Number LM2594M-3.3,

LM2594M-5.0, LM2594M-12 or

LM2594M-ADJ

LM2594HVM-3.3, LM2594HVM-5.0,

LM2594HVM-12 or LM2594HVM-ADJ

See NS Package Number M08A

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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.

Maximum Supply Voltage
LM2594 45V
LM2594HV 60V
ON /OFF Pin Input Voltage
Feedback Pin Voltage −0.3 ≤ V ≤+25V
Output Voltage to Ground

(Steady State) −1V
Power Dissipation Internally limited
Storage Temperature Range −65˚C to +150˚C
ESD Susceptibility

−0.3 ≤ V ≤ +25V

Human Body Model (Note 2) 2 kV
Lead Temperature
M8 Package

Vapor Phase (60 sec.) +215˚C

Infrared (15 sec.) +220˚C
N Package (Soldering, 10 sec.) +260˚C
Maximum Junction Temperature +150˚C

Operating Conditions

Temperature Range −40˚C ≤ TJ+125˚C
Supply Voltage

LM2594 4.5V to 40V

LM2594HV 4.5V to 60V

LM2594/LM2594HV-3.3
Electrical Characteristics

12V, I

=

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

J

Typ Limit

(Note 3) (Note 4)

Figure 1

INmax

, 0.1A ≤ I

≤ 0.5A 3.3 V

LOAD

3.168/3.135 V(min)

3.432/3.465 V(max)

=

0.5A 80

LOAD

(Limits)

%

Specifications with standard type face are for T
ture Range.V

=

40V for the LM2594 and 60V for the LM2594HV.

INmax

Symbol Parameter Conditions LM2594/LM2594HV-3.3 Units

SYSTEM PARAMETERS (Note 5) Test Circuit

V

OUT

η Efficiency V

Output Voltage 4.75V ≤ VIN≤ V

=

IN

LM2594/LM2594HV

LM2594/LM2594HV-5.0
Electrical Characteristics

12V, I

=

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

J

Typ Limit

(Note 3) (Note 4)

Figure 1

INmax

, 0.1A ≤ I

≤ 0.5A 5.0 V

LOAD

4.800/4.750 V(min)

5.200/5.250 V(max)

=

0.5A 82

LOAD

(Limits)

%

Specifications with standard type face are for T

ture Range

Symbol Parameter Conditions LM2594/LM2594HV-5.0 Units

SYSTEM PARAMETERS (Note 5) Test Circuit

V

OUT

η Efficiency V

Output Voltage 7V ≤ VIN≤ V

=

IN

LM2594/LM2594HV-12
Electrical Characteristics

25V, I

=

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

J

Typ Limit

(Note 3) (Note 4)

Figure 1

INmax

, 0.1A ≤ I

≤ 0.5A 12.0 V

LOAD

11.52/11.40 V(min)

12.48/12.60 V(max)

=

0.5A 88

LOAD

(Limits)

%

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Specifications with standard type face are for T

ture Range

Symbol Parameter Conditions LM2594/LM2594HV-12 Units

SYSTEM PARAMETERS (Note 5) Test Circuit

V

OUT

η Efficiency V

Output Voltage 15V ≤ VIN≤ V

=

IN

LM2594/LM2594HV-ADJ
Electrical Characteristics

Specifications with standard type face are for T

ture Range

Symbol Parameter Conditions LM2594/LM2594HV-ADJ Units

LM2594/LM2594HV

SYSTEM PARAMETERS (Note 5) Test Circuit

V

FB

η Efficiency V

Feedback Voltage 4.5V ≤ VIN≤ V

V

OUT

=

IN

=

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

J

Figure 1

, 0.1A ≤ I

INmax

LOAD

programmed for 3V. Circuit of

12V, I

=

0.5A 80

LOAD

Typ Limit

(Note 3) (Note 4)

≤ 0.5A 1.230 V

Figure 1

1.193/1.180 V(min)

1.267/1.280 V(max)

All Output Voltage Versions
Electrical Characteristics

Specifications with standard type face are for T
ture Range . Unless otherwise specified, V
sion. I

LOAD

=

100 mA

Symbol Parameter Conditions LM2594/LM2594HV-XX Units

DEVICE PARAMETERS

I

b

f

O

V

Feedback Bias Current Adjustable Version Only, VFB=1.3V 10 50/100 nA
Oscillator Frequency (Note 6) 150 kHz

Saturation Voltage I

SAT

DC Max Duty Cycle (ON) (Note 8) 100

Min Duty Cycle (OFF) (Note 9) 0

I

I

I

I

CL

L

Q

STBY

Current Limit Peak Current, (Note 7) (Note 8) 0.8 A

Output Leakage Current (Note 7) (Note 9) (Note 10) Output=0V 50 µA(max)

Quiescent Current (Note 9) 5 mA

Standby Quiescent ON/OFF pin=5V (OFF) (Note 10) 85 µA
Current LM2594 200/250 µA(max)

LM2594HV 140 250/300 µA(max)

θ

JA

Thermal Resistance N Package, Junction to Ambient (Note 11) 95 ˚C/W

M Package, Junction to Ambient (Note 11) 150

ON/OFF CONTROL Test Circuit

Figure 1

ON /OFF Pin Logic Input 1.3 V
V
V
I

H

Threshold Voltage Low (Regulator ON) 0.6 V(max)

IH
IL

High (Regulator OFF) 2.0 V(min)
ON /OFF Pin V
Input Current 15 µA(max)

I

L

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.

V

=

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

J

=

12V for the 3.3V, 5V, and Adjustable version and V

IN

=

24V for the 12V ver-

IN

Typ Limit

(Note 3) (Note 4)

127/110 kHz(min)
173/173 kHz(max)

=

0.5A (Note 7) (Note 8) 0.9 V

OUT

1.1/1.2 V(max)

0.65/0.58 A(min)

1.3/1.4 A(max)

Output=−1V 2 mA

15 mA(max)

10 mA(max)

=

2.5V (Regulator OFF) 5 µA

LOGIC

=

0.5V (Regulator ON) 0.02 µA

LOGIC

5 µA(max)

(Limits)

%

(Limits)

%

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All Output Voltage Versions
Electrical Characteristics

Note 2: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 3: Typical numbers are at 25˚C and represent the most likely norm.
Note 4: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%produc-

tion tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate
Average Outgoing Quality Level (AOQL).

Note 5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator sys­tem performance. When the LM2594/LM2594HV is used as shown in the
of Electrical Characteristics.

Note 6: The switching frequency is reduced when the second stage current limit is activated. The amount of reduction is determined by the severity of current over­load.

Note 7: No diode, inductor or capacitor connected to output pin.
Note 8: Feedback pin removed from output and connected to 0V to force the output transistor switch ON.
Note 9: Feedback pin removed from output and connected to 12V for the 3.3V,5V,and the ADJ. version, and 15V for the 12V version, to force the output transistor

switch OFF.

Note 10: V
Note 11: Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional copper area will

lower thermal resistance further. See application hints in this data sheet and the thermal model in Switchers Made Simple

=

40V for the LM2594 and 60V for the LM2594HV.

IN

(Continued)

Figure 1

test circuit, system performance will be as shown in system parameters section

®

software.

Typical Performance Characteristics

LM2594/LM2594HV

Normalized
Output Voltage

Switch Saturation
Voltage

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DS012439-7

Line Regulation

Switch Current Limit

DS012439-5

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Efficiency

DS012439-6

Dropout Voltage

DS012439-9

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Typical Performance Characteristics (Continued)

Quiescent Current

LM2594/LM2594HV

ON /OFF Threshold
Voltage

Feedback Pin
Bias Current

DS012439-10

DS012439-13

Standby
Quiescent Current

ON /OFF Pin
Current (Sinking)

DS012439-11

DS012439-14

Minimum Operating
Supply Voltage

DS012439-12

Switching Frequency

DS012439-15

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Typical Performance Characteristics

LM2594/LM2594HV

Continuous Mode Switching Waveforms

=

V

20V, V

IN

L=100 µH, C

A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.2A/div.
C: Output Ripple Voltage, 20 mV/div.

OUT

OUT

=

5V, I

=

LOAD

120 µF, C

=

400 mA

ESR=140 mΩ

OUT

Horizontal Time Base: 2 µs/div.

Load Transient Response for Continuous Mode

=

V

20V, V

IN

L=100 µH, C

OUT

OUT

=

5V, I

=

LOAD

120 µF, C

=

200 mA to 500 mA

ESR=140 mΩ

OUT

DS012439-17

Discontinuous Mode Switching Waveforms

=

V

20V, V

IN

L=33 µH, C

A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.2A/div.
C: Output Ripple Voltage, 20 mV/div.

OUT

OUT

=

5V, I

=

220 µF, C

LOAD

=

200 mA

ESR=60 mΩ

OUT

DS012439-18

Horizontal Time Base: 2 µs/div.

Load Transient Response for Discontinuous Mode

=

V

20V, V

IN

L=33 µH, C

OUT

OUT

=

5V, I

=

220 µF, C

=

100 mA to 200 mA

LOAD

OUT

ESR=60 mΩ

A: Output Voltage, 50 mV/div. (AC)
B: 200 mA to 500 mA Load Pulse

Horizontal Time Base: 50 µs/div.

DS012439-19

A: Output Voltage, 50 mV/div. (AC)
B: 100 mA to 200 mA Load Pulse

Horizontal Time Base: 200 µs/div.

DS012439-20

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Typical Circuit and Layout Guidelines

Fixed Output Voltage Versions

LM2594/LM2594HV

CIN— 68 µF, 35V, Aluminum Electrolytic Nichicon “PL Series”

— 120 µF, 25V Aluminum Electrolytic, Nichicon “PL Series”

C

OUT

D1 — 1A, 40V Schottky Rectifier, 1N5819
L1 — 100 µH, L20

DS012439-22

Select components with higher voltage ratings for designs using the LM2594HV with an input voltage between 40V and 60V.

Adjustable Output Voltage Versions

DS012439-23

CIN— 68 µF, 35V, Aluminum Electrolytic Nichicon “PL Series”

— 120 µF, 25V Aluminum Electrolytic, Nichicon “PL Series”

C

OUT

D1 — 1A, 40V Schottky Rectifier, 1N5819
L1 — 100 µH, L20
R

1

C

FF

%

—1kΩ,1

— SeeApplication Information Section

FIGURE 1. Typical Circuits and Layout Guides

As in any switching regulator, layout is very important. Rap­idly switching currents associated with wiring inductance can
generate voltage transients which can cause problems. For
minimal inductance and ground loops, the wires indicated by

heavy lines should be wide printed circuit traces and
should be kept as short as possible. For best results, ex-

ternal components should be located as close to the
switcher lC as possible using ground plane construction or
single point grounding.

If open core inductors are used, special care must be
taken as to the location and positioning of this type of induc­tor.Allowing the inductor flux to intersect sensitive feedback,
lC groundpath and C

wiring can cause problems.

OUT

When using the adjustable version, special care must be
taken as to the location of the feedback resistors and the as­sociated wiring. Physically locate both resistors near the IC,
and route the wiring away from the inductor, especially an
open core type of inductor. (See application section for more
information.)

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LM2594/LM2594HV Series Buck Regulator Design Procedure (Fixed
Output)

PROCEDURE (Fixed Output Voltage Version) EXAMPLE (Fixed Output Voltage Version)

Given:

=

V

Regulated Output Voltage (3.3V, 5V or 12V)

OUT

(max)=Maximum DC Input Voltage

V

IN

(max)=Maximum Load Current

I

LOAD

1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from

ures 4, 5

or

Figure 6

. (Output voltages of 3.3V, 5V, or 12V re-

Fig-

spectively.) For all other voltages, see the design procedure
for the adjustable version.

B. From the inductor value selection guide, identify the induc­tance region intersected by the Maximum Input Voltage line
and the Maximum Load Current line. Each region is identified
by an inductance value and an inductor code (LXX).

C. Select an appropriate inductor from the four manufactur­er’s part numbers listed in

2. Output Capacitor Selection (C

Figure 8

.

OUT

)

A. In the majority of applications, low ESR (Equivalent Series

Resistance) electrolytic capacitors between 82 µF and
220 µF and low ESR solid tantalum capacitors between 15
µF and 100 µF provide the best results. This capacitor should
be located close to the IC using short capacitor leads and
short copper traces. Do not use capacitors larger than
220 µF.

For additional information, see section on output capaci­tors in application information section.

B. To simplify the capacitor selection procedure, refer to the

quick design component selection table shown in

Figure 2

This table contains different input voltages, output voltages,
and load currents, and lists various inductors and output ca­pacitors that will provide the best design solutions.

C. The capacitor voltage rating for electrolytic capacitors
should be at least 1.5 times greater than the output voltage,
and often much higher voltage ratings are needed to satisfy
the low ESR requirements for low output ripple voltage.

D. For computer aided design software, see

Simple

version 4.1 or later.

Switchers Made

Given:

=

V

5V

OUT

(max)=12V

V

IN

(max)=0.4A

I

LOAD

1. Inductor Selection (L1)
A. Use the inductor selection guide for the 5V version shown

in

Figure 5

.

B. From the inductor value selection guide shown in
the inductance region intersected by the 12V horizontal line
and the 0.4A vertical line is 100 µH, and the inductor code is
L20.

C. The inductance value required is 100 µH. From the table
in

Figure 8

, go to the L20 line and choose an inductor part
number from any of the four manufacturers shown. (In most
instance, both through hole and surface mount inductors are
available.)

2. Output Capacitor Selection (C

OUT

)

A. See section on output capacitors in application infor­mation section.

B. From the quick design component selection table shown

in

Figure 2

, locate the 5V output voltage section. In the load
current column, choose the load current line that is closest to
the current needed in your application, for this example, use
the 0.5A line. In the maximum input voltage column, select
the line that covers the input voltage needed in your applica­tion, in this example, use the 15V line. Continuing on this line
are recommended inductors and capacitors that will provide
the best overall performance.

.

The capacitor list contains both through hole electrolytic and
surface mount tantalum capacitors from four different capaci­tor manufacturers. It is recommended that both the manufac­turers and the manufacturer’s series that are listed in the
table be used.

In this example aluminum electrolytic capacitors from several
different manufacturers are available with the range of ESR
numbers needed.

120 µF 25V Panasonic HFQ Series
120 µF 25V Nichicon PL Series

C. For a 5V output, a capacitor voltage rating at least 7.5V or
more is needed. But, in this example, even a low ESR,
switching grade, 120 µF 10V aluminum electrolytic capacitor
would exhibit approximately 400 mΩ of ESR (see the curve
in

Figure 14

for the ESR vs voltage rating). This amount of
ESR would result in relatively high output ripple voltage. To
reduce the ripple to 1%of the output voltage, or less, a ca­pacitor with a higher voltage rating (lower ESR) should be se­lected. A 16V or 25V capacitor will reduce the ripple voltage
by approximately half.

Figure 5

LM2594/LM2594HV

,

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