NSC LM2599T-12, LM2599SX-ADJ, LM2599SX-5.0, LM2599SX-3.3, LM2599SX-12 Datasheet

LM2599
SIMPLE SWITCHER

®

Power Converter 150 kHz 3A

Step-Down Voltage Regulator, with Features

General Description

The LM2599 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving a 3A 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.

This series of switching regulators is similar to the LM2596
series, with additionalsupervisory and performance features
added.

Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation

†

, improved line and load specifications,
fixed-frequency oscillator, Shutdown/Soft-start, error flag de­lay and error flag output.

The LM2599 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.
Available in a standard 7-lead TO-220 package with several
different lead bend options, and a 7-lead TO-263 Surface
mount package.

A standard series of inductors (both through hole and sur­face mount types) are available from several different manu­facturers optimized for use with the LM2599 series. This fea­ture greatly simplifies the design of switch-mode power
supplies.

Other features include a guaranteed

±

4%tolerance on out­put voltage under all conditions of input voltage and output
load conditions, and

±

15%on the oscillator frequency. Ex-

ternal shutdown is included, featuring typically 80 µA

standby current. Self protection features include a two stage
current limit for the output switch and an over temperature
shutdown for complete protection under fault conditions.

Features

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

±

4%max over line and load conditions

n Guaranteed 3A output current
n Available in 7-pin TO-220 and TO-263 (surface mount)

Package

n Input voltage range up to 40V
n 150 kHz fixed frequency internal oscillator
n Shutdown/Soft-start
n Out of regulation error flag
n Error output delay
n Low power standby mode, I

Q

typically 80 µA

n High Efficiency
n Uses readily available standard inductors
n Thermal shutdown and current limit protection

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 converter

Note:†Patent Number 5,382,918.

Typical Application (Fixed Output Voltage Versions)

SIMPLE SWITCHER®and

Switchers Made Simple

®

are registered trademarks of National Semiconductor Corporation.

DS012582-1

April 1998

LM2599 SIMPLE SWITCHER Power Converter 150 kHz 3A Step-Down Voltage Regulator, with

Features

© 2000 National Semiconductor Corporation DS012582 www.national.com

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 (V

IN

) 45V

SD /SS Pin Input Voltage (Note 2)

6V
Delay Pin Voltage (Note 2) 1.5V
Flag Pin Voltage −0.3 ≤ V ≤45V
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

Human Body Model (Note 3) 2 kV

Lead Temperature

S Package

Vapor Phase (60 sec.) +215˚C
Infrared (10 sec.) +245˚C

T Package (Soldering, 10 sec.) +260˚C

Maximum Junction Temperature +150˚C

Operating Conditions

Temperature Range −40˚C ≤ TJ≤ +125˚C
Supply Voltage 4.5V to 40V

LM2599-3.3
Electrical Characteristics

Specifications with standard type face are for T

J

=

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

ture Range.

Symbol Parameter Conditions LM2599-3.3 Units

(Limits)

Typ Limit

(Note 4) (Note 5)

SYSTEM PARAMETERS (Note 6) Test Circuit

Figure 1

V

OUT

Output Voltage 4.75V ≤ VIN≤ 40V, 0.2A ≤ I

LOAD

≤ 3A 3.3 V

3.168/3.135 V(min)

3.432/3.465 V(max)

η Efficiency V

IN

=

12V, I

LOAD

=

3A 73

%

LM2599-5.0
Electrical Characteristics

Specifications with standard type face are for T

J

=

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

ture Range.

Symbol Parameter Conditions LM2599-5.0 Units

(Limits)

Typ Limit

(Note 4) (Note 5)

SYSTEM PARAMETERS (Note 6) Test Circuit

Figure 1

V

OUT

Output Voltage 7V ≤ VIN≤ 40V, 0.2A ≤ I

LOAD

≤ 3A 5 V

4.800/4.750 V(min)

5.200/5.250 V(max)

η Efficiency V

IN

=

12V, I

LOAD

=

3A 80

%

LM2599

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LM2599-12
Electrical Characteristics

Specifications with standard type face are for T

J

=

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

ture Range.

Symbol Parameter Conditions LM2599-12 Units

(Limits)

Typ Limit

(Note 4) (Note 5)

SYSTEM PARAMETERS (Note 6) Test Circuit

Figure 1

V

OUT

Output Voltage 15V ≤ VIN≤ 40V, 0.2A ≤ I

LOAD

≤ 3A 12 V

11.52/11.40 V(min)

12.48/12.60 V(max)

η Efficiency V

IN

=

25V, I

LOAD

=

3A 90

%

LM2599-ADJ
Electrical Characteristics

Specifications with standard type face are for T

J

=

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

Range.

Symbol Parameter Conditions LM2599-ADJ Units

(Limits)

Typ Limit

(Note 4) (Note 5)

SYSTEM PARAMETERS (Note 6) Test Circuit

Figure 1

V

FB

Feedback Voltage 4.5V ≤ VIN≤ 40V, 0.2A ≤ I

LOAD

≤ 3A 1.230 V

V

OUT

programmed for 3V. Circuit of

Figure 1

. 1.193/1.180 V(min)

1.267/1.280 V(max)

η Efficiency V

IN

=

12V, V

OUT

=

3V, I

LOAD

=

3A 73

%

All Output Voltage Versions
Electrical Characteristics

Specifications with standard type face are for T

J

=

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

ture Range. Unless otherwise specified, V

IN

=

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

IN

=

24V for the 12V ver-

sion. I

LOAD

=

500 mA

Symbol Parameter Conditions LM2599-XX Units

(Limits)

Typ Limit

(Note4)(Note 5)

DEVICE PARAMETERS

I

b

Feedback Bias Current Adjustable Version Only, V

FB

=

1.3V 10 nA
50/100 nA (max)

f

O

Oscillator Frequency (Note 7) 150 kHz

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

V

SAT

Saturation Voltage I

OUT

=

3A (Note 8) (Note 9) 1.16 V

1.4/1.5 V(max)

DC Max Duty Cycle (ON) (Note 9) 100

%

Min Duty Cycle (OFF) (Note 10) 0

I

CL

Current Limit Peak Current, (Note 8) (Note 9) 4.5 A

3.6/3.4 A(min)

6.9/7.5 A(max)

I

L

Output Leakage Current (Note 8) (Note 10) (Note 11) Output=0V 50 µA(max)

Output=−1V 2 mA

30 mA(max)

I

Q

Operating Quiescent SD /SS Pin Open (Note 10) 5mA
Current 10 mA(max)

LM2599

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All Output Voltage Versions
Electrical Characteristics

(Continued)

Specifications with standard type face are for T

J

=

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

ture Range. Unless otherwise specified, V

IN

=

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

IN

=

24V for the 12V ver-

sion. I

LOAD

=

500 mA

Symbol Parameter Conditions LM2599-XX Units

(Limits)

Typ Limit

(Note4)(Note 5)

DEVICE PARAMETERS

I

STBY

Standby Quiescent SD /SS pin=0V (Note 11) 80 µA
Current 200/250 µA(max)

θ

JC

Thermal Resistance TO220 or TO263 Package, Junction to Case 2 ˚C/W

θ

JA

TO220 Package, Juncton to Ambient (Note 12) 50 ˚C/W

θ

JA

TO263 Package, Juncton to Ambient (Note 13) 50 ˚C/W

θ

JA

TO263 Package, Juncton to Ambient (Note 14) 30 ˚C/W

θ

JA

TO263 Package, Juncton to Ambient (Note 15) 20 ˚C/W

SHUTDOWN/SOFT-START CONTROL Test Circuit of

Figure 1

V

SD

Shutdown Threshold 1.3 V
Voltage Low, (Shutdown Mode) 0.6 V(max)

High, (Soft-start Mode) 2 V(min)

V

SS

Soft-start Voltage V

OUT

=

20%of Nominal Output Voltage 2 V

V

OUT

=

100%of Nominal Output Voltage 3

I

SD

Shutdown Current V

SHUTDOWN

=

0.5V

5µA

10 µA(max)

I

SS

Soft-start Current V

Soft-start

=

2.5V 1.6 µA
5 µA(max)

FLAG/DELAY CONTROL Test Circuit of

Figure 1

Regulator Dropout Detector Low (Flag ON) 96

%

Threshold Voltage 92

%

(min)

98

%

(max)

VF

SAT

Flag Output Saturation I

SINK

=

3 mA 0.3 V

Voltage V

DELAY

=

0.5V 0.7/1.0 V(max)

IF

L

Flag Output Leakage Current V

FLAG

=

40V 0.3 µA
Delay Pin Threshold 1.25 V
Voltage Low (Flag ON) 1.21 V(min)

High (Flag OFF) and V

OUT

Regulated 1.29 V(max)

Delay Pin Source Current V

DELAY

=

0.5V 3 µA
6 µA(max)

Delay Pin Saturation Low (Flag ON) 55 mV

350/400 mV(max)

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.

Note 2: Voltage internally clamped. If clamp voltage is exceeded, limit current to a maximum of 1 mA.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.
Note 4: Typical numbers are at 25˚C and represent the most likely norm.
Note 5: All limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%pro-

duction 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 6: External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the LM2599
is used as shown in the

Figure 1

test circuit, system performance will be as shown in system parameters section of Electrical Characteristics.

Note 7: 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 8: No diode, inductor or capacitor connected to output pin.
Note 9: Feedback pin removed from output and connected to 0V to force the output transistor switch ON.

LM2599

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All Output Voltage Versions
Electrical Characteristics

(Continued)

Note 10: 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 11: V

IN

=

40V.

Note 12: Junction to ambient thermal resistance (no external heat sink) for the package mounted TO-220 package mounted vertically, with the leads soldered to a
printed circuit board with (1 oz.) copper area of approximately 1 in

2

.

Note 13: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 0.5 in

2

of (1 oz.) copper area.

Note 14: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 2.5 in

2

of (1 oz.) copper area.

Note 15: Junction to ambient thermal resistance with the TO-263 package tab soldered to a double sided printed circuit board with 3 in

2

of (1 oz.) copper area on

the LM2599S side of the board, and approximately 16 in

2

of copper on the other side of the p-c board. See application hints in this data sheet and the thermal model

in Switchers Made Simple version 4.2.1 (or later) software.

Typical Performance Characteristics (Circuit of

Figure 1

)

Normalized
Output Voltage

DS012582-2

Line Regulation

DS012582-3

Efficiency

DS012582-4

Switch Saturation
Voltage

DS012582-5

Switch Current Limit

DS012582-6

Dropout Voltage

DS012582-7

Operating
Quiescent Current

DS012582-8

Shutdown
Quiescent Current

DS012582-9

Minimum Operating
Supply Voltage

DS012582-10

LM2599

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Typical Performance Characteristics (Circuit of

Figure 1

) (Continued)

Feedback Pin
Bias Current

DS012582-11

Flag Saturation
Voltage

DS012582-12

Switching Frequency

DS012582-13

Soft-start

DS012582-14

Shutdown /Soft-start
Current

DS012582-15

Daisy Pin Current

DS012582-16

Soft-start Response

DS012582-18

Shutdown/Soft-start
Threshold Voltage

DS012582-53

LM2599

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Typical Performance Characteristics (Circuit of

Figure 1

) (Continued)

Connection Diagrams and Order Information

Continuous Mode Switching Waveforms
V

IN

=

20V, V

OUT

=

5V, I

LOAD

=

2A

L=32 µH, C

OUT

=

220 µF, C

OUT

ESR=50 mΩ

DS012582-20

A: Output Pin Voltage, 10V/div.
B: Inductor Current 1A/div.
C: Output Ripple Voltage, 50 mV/div.

Horizontal Time Base: 2 µs/div.

Discontinuous Mode Switching Waveforms
V

IN

=

20V, V

OUT

=

5V, I

LOAD

=

500 mA

L=10 µH, C

OUT

=

330 µF, C

OUT

ESR=45 mΩ

DS012582-19

A: Output Pin Voltage, 10V/div.
B: Inductor Current 0.5A/div.
C: Output Ripple Voltage, 100 mV/div.

Horizontal Time Base: 2 µs/div.

Load Transient Response for Continuous Mode
V

IN

=

20V, V

OUT

=

5V, I

LOAD

=

500 mA to 2A

L=32 µH, C

OUT

=

220 µF, C

OUT

ESR=50 mΩ

DS012582-21

A: Output Voltage, 100 mV/div. (AC)
B: 500 mA to 2A Load Pulse

Horizontal Time Base: 50 µs/div.

Load Transient Response for Discontinuous Mode
V

IN

=

20V, V

OUT

=

5V, I

LOAD

=

500 mA to 2A

L=10 µH, C

OUT

=

330 µF, C

OUT

ESR=45 mΩ

DS012582-22

A: Output Voltage, 100 mV/div. (AC)
B: 500 mA to 2A Load Pulse

Horizontal Time Base: 200 µs/div.

Bent and Staggered Leads, Through Hole Package

7-Lead TO-220 (T)

DS012582-50

Order Number LM2599T-3.3, LM2599T-5.0,

LM2599T-12 or LM2599T-ADJ

See NS Package Number TA07B

Surface Mount Package

7-Lead TO-263 (S)

DS012582-23

Order Number LM2599S-3.3, LM2599S-5.0,

LM2599S-12 or LM2599S-ADJ

See NS Package Number TS7B

LM2599

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Test Circuit and Layout Guidelines

Fixed Output Voltage Versions

DS012582-24

Component Values shown are for V

IN

=

15V,

V

OUT

=

5V, I

LOAD

=

3A.

C

IN

— 470 µF, 50V,Aluminum Electrolytic Nichicon “PL Series”

C

OUT

— 220 µF, 25V Aluminum Electrolytic, Nichicon “PL Series”
D1 — 5A, 40V Schottky Rectifier, 1N5825
L1 — 68 µH, L38

Typical Values

CSS— 0.1 µF
C

DELAY

— 0.1 µF

R

Pull Up

— 4.7k

LM2599

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Test Circuit and Layout Guidelines (Continued)

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

OUT

wiring can cause problems.

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.)

Adjustable Output Voltage Versions

DS012582-25

where V

REF

=

1.23V

Select R1to be approximately 1 kΩ,usea1%resistor for best stability.
Component Values shown are for V

IN

=

20V,

V

OUT

=

10V, I

LOAD

=

3A.

C

IN

: — 470 µF, 35V,Aluminum Electrolytic Nichicon “PL Series”

C

OUT

: — 220 µF, 35V Aluminum Electrolytic, Nichicon “PL Series”
D1 — 5A, 30V Schottky Rectifier, 1N5824
L1 — 68 µH, L38
R

1

—1kΩ,1

%

R

2

— 7.15k, 1

%

C

FF

— 3.3 nF, See Application Information Section

R

FF

—3kΩ, See Application Information Section

Typical Values

CSS— 0.1 µF
C

DELAY

— 0.1 µF

R

PULL UP

— 4.7k

FIGURE 1. Standard Test Circuits and Layout Guides

LM2599

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LM2599 Series Buck Regulator Design Procedure (Fixed Output)

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

Given:

V

OUT

=

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

V

IN

(max)=Maximum DC Input Voltage

I

LOAD

(max)=Maximum Load Current

Given:

V

OUT

=

5V

V

IN

(max)=12V

I

LOAD

(max)=3A

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

Fig-

ure 4

,

Figure 5

,or6.(Output voltages of 3.3V, 5V, or 12V re­spectively.) 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

Figure 8

.

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

Figure 5

,
the inductance region intersected by the 12V horizontal line
and the 3A vertical line is 33 µH, and the inductor code is
L40.

C. The inductance value required is 33 µH. From the table in

Figure 8

, go to the L40 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. In the majority of applications, low ESR (Equivalent Series

Resistance) electrolytic capacitors between 82 µF and 820
µF and low ESR solid tantalum capacitors between 10 µF
and 470 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 820 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

Switchers

Made Simple

(version 4.2.1 or later).

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 3A 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.

330 µF 35V Panasonic HFQ Series
330 µF 35V Nichicon PL Series

C. For a 5V output, a capacitor voltage rating at least 7.5V or
more is needed. But even a low ESR, switching grade, 220
µF 10V aluminum electrolytic capacitor would exhibit ap­proximately 225 mΩ of ESR (see the curve in

Figure 16

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
value or with a higher voltage rating (lower ESR) should be
selected. A 16V or 25V capacitor will reduce the ripple volt­age by approximately half.

LM2599

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