National Semiconductor LM2599 Technical data

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LM2599
SIMPLE SWITCHER

®

Power Converter 150 kHz 3A

Step-Down Voltage Regulator, with Features

December 2000

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
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
put voltage under all conditions of input voltage and output
load conditions, and
ternal shutdown is included, featuring typically 80 µA

†

, improved line and load specifications,

±

4% tolerance on out-

±

15% on the oscillator frequency. Ex-

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

typically 80 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 converter

Note:†Patent Number 5,382,918.

Typical Application (Fixed Output Voltage Versions)

DS012582-1

SIMPLE SWITCHER®and

© 2001 National Semiconductor Corporation DS012582 www.national.com

Switchers Made Simple

®

are registered trademarks of National Semiconductor Corporation.

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

LM2599

please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Maximum Supply Voltage (V
SD /SS Pin Input Voltage (Note 2)
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

) 45V

IN

6V

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 TJ= 25˚C, and those with boldface type apply over full Operating Tempera­ture Range.

Symbol Parameter Conditions LM2599-3.3 Units

Typ Limit

(Note 4) (Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit
V

OUT

η Efficiency V

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

IN

= 12V, I

Figure 1

≤ 3A 3.3 V

LOAD

3.168/3.135 V(min)

3.432/3.465 V(max)

=3A 73 %

LOAD

(Limits)

LM2599-5.0
Electrical Characteristics

Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Tempera­ture Range.

Symbol Parameter Conditions LM2599-5.0 Units

Typ Limit

(Note 4) (Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit
V

OUT

η Efficiency V

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

IN

= 12V, I

Figure 1

≤ 3A 5 V

LOAD

4.800/4.750 V(min)

5.200/5.250 V(max)

=3A 80 %

LOAD

(Limits)

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LM2599-12
Electrical Characteristics

Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Tempera­ture Range.

Symbol Parameter Conditions LM2599-12 Units

Typ Limit

(Limits)

(Note 4) (Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit
V

OUT

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

Figure 1

≤ 3A 12 V

LOAD

11.52/11.40 V(min)

12.48/12.60 V(max)

η Efficiency V

= 25V, I

IN

=3A 90 %

LOAD

LM2599-ADJ
Electrical Characteristics

Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Tempera­ture Range.

Symbol Parameter Conditions LM2599-ADJ Units

Typ Limit

(Note 4) (Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit
V

FB

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

V

programmed for 3V. Circuit of

OUT

Figure 1

≤ 3A 1.230 V

LOAD

Figure 1

. 1.193/1.180 V(min)

1.267/1.280 V(max)

η Efficiency V

= 12V, V

IN

OUT

= 3V, I

=3A 73 %

LOAD

(Limits)

LM2599

All Output Voltage Versions
Electrical Characteristics

Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Tempera­ture Range. Unless otherwise specified, V

sion. I

LOAD

= 500 mA

Symbol Parameter Conditions LM2599-XX Units

DEVICE PARAMETERS

I

b

f

O

V

SAT

Feedback Bias Current Adjustable Version Only, VFB= 1.3V 10 nA

Oscillator Frequency (Note 7) 150 kHz

Saturation Voltage I

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

Min Duty Cycle (OFF) (Note 10) 0

I

CL

I

L

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

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

= 12V for the 3.3V, 5V, and Adjustable version and VIN= 24V for the 12V ver-

IN

Typ Limit

(Note4)(Note 5)

50/100 nA (max)

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

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

OUT

1.4/1.5 V(max)

3.6/3.4 A(min)

6.9/7.5 A(max)

Output = −1V 2 mA

30 mA(max)

(Limits)

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All Output Voltage Versions
Electrical Characteristics

LM2599

Specifications with standard type face are for TJ= 25˚C, and those with boldface type apply over full Operating Tempera­ture Range. Unless otherwise specified, V

sion. I

LOAD

= 500 mA

Symbol Parameter Conditions LM2599-XX Units

DEVICE PARAMETERS

I

Q

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

I

STBY

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

θ

JC

θ

JA

θ

JA

θ

JA

θ

JA

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

SHUTDOWN/SOFT-START CONTROL Test Circuit of
V

SD

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

V

SS

I

SD

I

SS

Soft-start Voltage V

Shutdown Current V

Soft-start Current V

FLAG/DELAY CONTROL Test Circuit of

Regulator Dropout Detector Low (Flag ON) 96 %
Threshold Voltage 92 %(min)

VF

SAT

Flag Output Saturation I
Voltage V

IF

L

Flag Output Leakage Current V
Delay Pin Threshold 1.25 V
Voltage Low (Flag ON) 1.21 V(min)

Delay Pin Source Current V

Delay Pin Saturation Low (Flag ON) 55 mV

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%

production 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

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.

Figure 1

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

(Continued)

= 12V for the 3.3V, 5V, and Adjustable version and VIN= 24V for the 12V ver-

IN

Typ Limit

(Note4)(Note 5)

TO220 Package, Juncton to Ambient (Note 12) 50 ˚C/W
TO263 Package, Juncton to Ambient (Note 13) 50 ˚C/W
TO263 Package, Juncton to Ambient (Note 14) 30 ˚C/W
TO263 Package, Juncton to Ambient (Note 15) 20 ˚C/W

Figure 1

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

= 20% of Nominal Output Voltage 2 V

OUT

V

= 100% of Nominal Output Voltage 3

OUT
SHUTDOWN

= 0.5V 5µA

10 µA(max)

Soft-start

= 2.5V 1.6 µA

5 µA(max)

Figure 1

98 %(max)

= 3 mA 0.3 V

SINK

= 0.5V 0.7/1.0 V(max)

DELAY

= 40V 0.3 µA

FLAG

High (Flag OFF) and V

= 0.5V 3 µA

DELAY

Regulated 1.29 V(max)

OUT

6 µA(max)

350/400 mV(max)

(Limits)

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All Output Voltage Versions
Electrical Characteristics

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.
Note 10: Feedback pin removed from output and connected to12Vfor the 3.3V, 5V, and the ADJ. version,and 15V for the 12V version, to force the output transistor

switch OFF.

Note 11: V
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

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

the LM2599S side of the board, and approximately 16 in
in Switchers Made Simple version 4.2.1 (or later) software.

IN

= 40V.

(Continued)

2

.

2

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

2

of (1 oz.) copper area.

2

of (1 oz.) copper area.

2

of (1 oz.) copper area on

LM2599

Typical Performance Characteristics (Circuit of

Normalized
Output Voltage

DS012582-2

Switch Saturation
Voltage

Line Regulation

Switch Current Limit

Figure 1

DS012582-3

)

Efficiency

DS012582-4

Dropout Voltage

Operating
Quiescent Current

DS012582-5

DS012582-8

Shutdown
Quiescent Current

DS012582-6

DS012582-9

DS012582-7

Minimum Operating
Supply Voltage

DS012582-10

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Typical Performance Characteristics (Circuit of

LM2599

Feedback Pin
Bias Current

Flag Saturation
Voltage

Figure 1

) (Continued)

Switching Frequency

Soft-start

Soft-start Response

DS012582-11

DS012582-14

Shutdown /Soft-start
Current

Shutdown/Soft-start
Threshold Voltage

DS012582-12

DS012582-13

Daisy Pin Current

DS012582-16

DS012582-15

DS012582-18

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DS012582-53

LM2599

Typical Performance Characteristics (Circuit of

Continuous Mode Switching Waveforms
V

= 20V, V

IN

L = 32 µH, C

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

OUT

OUT

=5V,I

LOAD

= 220 µF, C

=2A

ESR=50mΩ

OUT

Horizontal Time Base: 2 µs/div.

Load Transient Response for Continuous Mode
V

= 20V, V

IN

L = 32 µH, C

OUT

OUT

=5V,I

LOAD

= 220 µF, C

= 500 mA to 2A

ESR=50mΩ

OUT

DS012582-20

Discontinuous Mode Switching Waveforms

= 20V, V

V

IN

L = 10 µH, C

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

Load Transient Response for Discontinuous Mode

= 20V, V

V

IN

L = 10 µH, C

Figure 1

OUT

OUT

=5V,I

) (Continued)

LOAD

= 330 µF, C

= 500 mA

ESR=45mΩ

OUT

Horizontal Time Base: 2 µs/div.

OUT

OUT

=5V,I

= 330 µF, C

= 500 mA to 2A

LOAD

OUT

ESR=45mΩ

DS012582-19

DS012582-21

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

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

Horizontal Time Base: 50 µs/div.

Connection Diagrams and Order Information

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

Order Number LM2599S-3.3, LM2599S-5.0,

DS012582-22

Horizontal Time Base: 200 µs/div.

Surface Mount Package

7-Lead TO-263 (S)

DS012582-23

LM2599S-12 or LM2599S-ADJ

See NS Package Number TS7B

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Test Circuit and Layout Guidelines

LM2599

Component Values shown are for VIN= 15V,

=5V,I

V

OUT

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

C

IN

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

C

OUT

D1 — 5A, 40V Schottky Rectifier, 1N5825
L1 — 68 µH, L38

Typical Values

CSS— 0.1 µF
C

DELAY

R

Pull Up

= 3A.

LOAD

— 0.1 µF
— 4.7k

Fixed Output Voltage Versions

DS012582-24

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Test Circuit and Layout Guidelines (Continued)

Adjustable Output Voltage Versions

LM2599

DS012582-25

where V

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

OUT

C

IN

C

OUT

D1 — 5A, 30V Schottky Rectifier, 1N5824
L1 — 68 µH, L38
R

1

R

2

C

FF

R

FF

Typical Values

CSS—0.1 µF
C

DELAY

R

PULL UP

= 1.23V

REF

= 20V,

= 10V, I

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

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

—1kΩ,1%
— 7.15k, 1%

— 3.3 nF, See Application Information Section
—3kΩ, See Application Information Section

—0.1 µF

—4.7k

LOAD

= 3A.

IN

FIGURE 1. Standard Test 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,

external 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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LM2599 Series Buck Regulator Design Procedure (Fixed Output)

LM2599

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

Given:

V

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

OUT

V

(max) = Maximum DC Input Voltage

IN

I

(max) = Maximum Load Current

LOAD

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

Figure 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

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 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

Made Simple

(version 4.2.1 or later).

Switchers

Given:

=5V

V

OUT

V

(max) = 12V

IN

I

(max) = 3A

LOAD

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

Figure 5

in

.

B. From the inductor value selection guide shown in
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
A. See section on output capacitors in application infor-

mation 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
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.

OUT

Figure 5

,

)

Figure 17

for

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