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

April 1998

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 additional supervisory and performance features added.

Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation², 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. External 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

n3.3V, 5V, 12V, and adjustable output versions

nAdjustable version output voltage range, 1.2V to 37V

±4% max over line and load conditions

nGuaranteed 3A output current

nAvailable in 7-pin TO-220 and TO-263 (surface mount) Package

nInput voltage range up to 40V

n150 kHz fixed frequency internal oscillator

nShutdown/Soft-start

nOut of regulation error flag

nError output delay

nLow power standby mode, IQ typically 80 µA

nHigh Efficiency

nUses readily available standard inductors

nThermal shutdown and current limit protection

Applications

nSimple high-efficiency step-down (buck) regulator

nEfficient pre-regulator for linear regulators

nOn-card switching regulators

nPositive to Negative converter

Note: ² Patent Number 5,382,918.

Typical Application (Fixed Output Voltage Versions)

DS012582-1

SIMPLE SWITCHER® and Switchers Made Simple® are registered trademarks of National Semiconductor Corporation.

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

Features

© 2000 National Semiconductor Corporation

DS012582

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LM2599

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 (VIN)			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		−65ÊC to +150ÊC

ESD Susceptibility
Human Body Model (Note 3)	2 kV
Lead Temperature
S Package
Vapor Phase (60 sec.)	+215ÊC
Infrared (10 sec.)	+245ÊC
T Package (Soldering, 10 sec.)	+260ÊC
Maximum Junction Temperature	+150ÊC

Operating Conditions

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

LM2599-3.3

Electrical Characteristics

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

Symbol	Parameter	Conditions	LM2599-3.3		Units
					(Limits)
			Typ	Limit
			(Note 4)	(Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit Figure 1
VOUT	Output Voltage	4.75V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 3A	3.3		V
				3.168/3.135	V(min)
				3.432/3.465	V(max)
η	Efficiency	VIN = 12V, ILOAD = 3A	73		%

LM2599-5.0

Electrical Characteristics

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

Symbol	Parameter	Conditions		LM2599-5.0		Units
						(Limits)
			Typ		Limit
			(Note 4)		(Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit Figure 1
VOUT	Output Voltage	7V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 3A	5			V
					4.800/4.750	V(min)
					5.200/5.250	V(max)
η	Efficiency	VIN = 12V, ILOAD = 3A	80			%

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LM2599-12

Electrical Characteristics

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

Symbol	Parameter	Conditions		LM2599-12		Units
						(Limits)
			Typ		Limit
			(Note 4)		(Note 5)
SYSTEM PARAMETERS (Note 6) Test Circuit Figure 1
VOUT	Output Voltage	15V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 3A	12			V
					11.52/11.40	V(min)
					12.48/12.60	V(max)
η	Efficiency	VIN = 25V, ILOAD = 3A	90			%

LM2599-ADJ

Electrical Characteristics

Specifications with standard type face are for TJ = 25ÊC, 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
VFB	Feedback Voltage	4.5V ≤ VIN ≤ 40V, 0.2A ≤ ILOAD ≤ 3A	1.230		V
		VOUT programmed for 3V. Circuit of Figure 1.		1.193/1.180	V(min)
				1.267/1.280	V(max)
η	Efficiency	VIN = 12V, VOUT = 3V, ILOAD = 3A	73		%

All Output Voltage Versions Electrical Characteristics

Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the 12V version. ILOAD = 500 mA

Symbol	Parameter			Conditions		LM2599-XX		Units
								(Limits)
						Typ	Limit
						(Note	(Note 5)
						4)
DEVICE PARAMETERS
Ib	Feedback Bias Current		Adjustable Version Only, VFB = 1.3V			10		nA
							50/100	nA (max)
fO	Oscillator Frequency		(Note 7)			150		kHz
							127/110	kHz(min)
							173/173	kHz(max)
VSAT	Saturation Voltage		IOUT = 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
ICL	Current Limit		Peak Current, (Note 8) (Note 9)			4.5		A
							3.6/3.4	A(min)
							6.9/7.5	A(max)
IL	Output Leakage Current		(Note 8) (Note 10) (Note 11)		Output = 0V		50	µA(max)
					Output = −1V	2		mA
							30	mA(max)
IQ	Operating Quiescent					5		mA
			SD	/SS Pin Open (Note 10)
	Current						10	mA(max)

LM2599

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LM2599

All Output Voltage Versions

Electrical Characteristics (Continued)

Specifications with standard type face are for TJ = 25ÊC, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable version and VIN = 24V for the 12V version. ILOAD = 500 mA

Symbol	Parameter					Conditions		LM2599-XX		Units
										(Limits)
								Typ	Limit
								(Note	(Note 5)
								4)
DEVICE PARAMETERS
ISTBY	Standby Quiescent		SD		/SS pin = 0V		(Note 11)	80		µA
	Current								200/250	µA(max)
θJC	Thermal Resistance		TO220 or TO263 Package, Junction to Case					2		ÊC/W
θJA			TO220 Package, Juncton to Ambient (Note 12)					50		ÊC/W
θJA			TO263 Package, Juncton to Ambient (Note 13)					50		ÊC/W
θJA			TO263 Package, Juncton to Ambient (Note 14)					30		ÊC/W
θJA			TO263 Package, Juncton to Ambient (Note 15)					20		ÊC/W
SHUTDOWN/SOFT-START CONTROL Test Circuit of Figure 1
VSD	Shutdown Threshold							1.3		V
	Voltage	Low, (Shutdown Mode)							0.6	V(max)
		High, (Soft-start Mode)							2	V(min)
VSS	Soft-start Voltage		VOUT = 20% of Nominal Output Voltage					2		V
			VOUT = 100% of Nominal Output Voltage					3
ISD	Shutdown Current		V			= 0.5V		5		µA
				SHUTDOWN
									10	µA(max)
ISS	Soft-start Current		VSoft-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)
VFSAT	Flag Output Saturation		ISINK = 3 mA					0.3		V
	Voltage		VDELAY = 0.5V						0.7/1.0	V(max)
IFL	Flag Output Leakage Current		VFLAG = 40V					0.3		µA
	Delay Pin Threshold							1.25		V
	Voltage		Low (Flag ON)						1.21	V(min)
			High (Flag OFF) and VOUT Regulated						1.29	V(max)
	Delay Pin Source Current		VDELAY = 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 25ÊC 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 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.

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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: VIN = 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 in2.

Note 13: Junction to ambient thermal resistance with the TO-263 package tab soldered to a single sided printed circuit board with 0.5 in2 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 in2 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 in2 of (1 oz.) copper area on the LM2599S side of the board, and approximately 16 in2 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	Line Regulation	Efficiency
Output Voltage

	DS012582-3	DS012582-4
	DS012582-2
Switch Saturation	Switch Current Limit	Dropout Voltage
Voltage

	DS012582-6	DS012582-7
	DS012582-5
Operating	Shutdown	Minimum Operating
Quiescent Current	Quiescent Current	Supply Voltage

DS012582-8	DS012582-9	DS012582-10

LM2599

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LM2599

Typical Performance Characteristics (Circuit of Figure 1) (Continued)

Feedback Pin	Flag Saturation	Switching Frequency
Bias Current	Voltage

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DS012582-11	DS012582-12

Soft-start	Shutdown /Soft-start	Daisy Pin Current
	Current

	DS012582-14
			DS012582-16
		DS012582-15
Soft-start Response
	Shutdown/Soft-start
	Threshold Voltage

DS012582-18

DS012582-53

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Typical Performance Characteristics (Circuit of Figure 1) (Continued)

Continuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 2A	Discontinuous Mode Switching Waveforms
L = 32 µH, C OUT = 220 µF, C OUT ESR = 50 mΩ	VIN = 20V, VOUT = 5V, ILOAD = 500 mA
	L = 10 µH, C OUT = 330 µF, C OUT ESR = 45 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.

Load Transient Response for Continuous Mode

VIN = 20V, VOUT = 5V, ILOAD = 500 mA to 2A

L = 32 µH, C OUT = 220 µF, C OUT ESR = 50 mΩ

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A:Output Voltage, 100 mV/div. (AC)

B:500 mA to 2A Load Pulse

Horizontal Time Base: 50 µs/div.

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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 Discontinuous Mode

VIN = 20V, VOUT = 5V, ILOAD = 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.

Connection Diagrams and Order Information

Bent and Staggered Leads, Through Hole Package

7-Lead TO-220 (T) Surface Mount Package 7-Lead TO-263 (S)

	DS012582-50
	Order Number LM2599T-3.3, LM2599T-5.0,	DS012582-23
		Order Number LM2599S-3.3, LM2599S-5.0,
	LM2599T-12 or LM2599T-ADJ
		LM2599S-12 or LM2599S-ADJ
	See NS Package Number TA07B
		See NS Package Number TS7B

LM2599

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LM2599

Test Circuit and Layout Guidelines

Fixed Output Voltage Versions

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Component Values shown are for VIN = 15V,

VOUT = 5V, ILOAD = 3A.

CIN	Ð	470	µF, 50V, Aluminum Electrolytic Nichicon ªPL Seriesº
COUT		Ð 220 µF, 25V Aluminum Electrolytic, Nichicon ªPL Seriesº
D1	Ð	5A, 40V Schottky Rectifier, 1N5825
L1	Ð	68 µH, L38
Typical Values
CSS	Ð	0.1	µF
CDELAY		Ð	0.1 µF
RPull Up		Ð	4.7k

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Test Circuit and Layout Guidelines (Continued)

Adjustable Output Voltage Versions

DS012582-25

where VREF = 1.23V

Select R1 to be approximately 1 kΩ, use a 1% resistor for best stability.

Component Values shown are for VIN = 20V,

VOUT = 10V, ILOAD = 3A.

CIN: Ð 470 µF, 35V, Aluminum Electrolytic Nichicon ªPL Seriesº

COUT: Ð 220 µF, 35V Aluminum Electrolytic, Nichicon ªPL Seriesº

D1 Ð 5A, 30V Schottky Rectifier, 1N5824

L1 Ð 68 µH, L38

R1 Ð 1 k Ω, 1%

R2 Ð 7.15k, 1 %

CFF Ð 3.3 nF, See Application Information Section

RFF Ð 3 k Ω, See Application Information Section

Typical Values

CSS Ð 0.1 µF

CDELAY Ð 0.1 µF

RPULL UP Ð 4.7k

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 COUT 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.)

LM2599

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LM2599

LM2599 Series Buck Regulator Design Procedure (Fixed Output)

	PROCEDURE (Fixed Output Voltage Version)	EXAMPLE (Fixed Output Voltage Version)
	Given:	Given:
	VOUT = Regulated Output Voltage (3.3V, 5V or 12V)	VOUT = 5V
	VIN(max) = Maximum DC Input Voltage	VIN(max) = 12V
	ILOAD(max) = Maximum Load Current	ILOAD(max) = 3A
	1. Inductor Selection (L1)	1. Inductor Selection (L1)
	A. Select the correct inductor value selection guide from Fig-	A. Use the inductor selection guide for the 5V version shown
	ure 4, Figure 5, or 6. (Output voltages of 3.3V, 5V, or 12V re-	in Figure 5.
	spectively.) For all other voltages, see the design procedure	B. From the inductor value selection guide shown in Figure 5,
	for the adjustable version.	the inductance region intersected by the 12V horizontal line
	B. From the inductor value selection guide, identify the induc-	and the 3A vertical line is 33 µH, and the inductor code is
	tance region intersected by the Maximum Input Voltage line	L40.
	and the Maximum Load Current line. Each region is identified	C. The inductance value required is 33 µH. From the table in
	by an inductance value and an inductor code (LXX).	Figure 8, go to the L40 line and choose an inductor part num-
	C. Select an appropriate inductor from the four manufactur-	ber from any of the four manufacturers shown. (In most in-
	er's part numbers listed in Figure 8.	stance, both through hole and surface mount inductors are
		available.)
	2. Output Capacitor Selection (COUT)	2. Output Capacitor Selection (COUT)
	A. In the majority of applications, low ESR (Equivalent Series	A. See section on output capacitors in application infor-
	Resistance) electrolytic capacitors between 82 µF and 820	mation section.
	µF and low ESR solid tantalum capacitors between 10 µF	B. From the quick design component selection table shown
	and 470 µF provide the best results. This capacitor should be	in Figure 2, locate the 5V output voltage section. In the load
	located close to the IC using short capacitor leads and short	current column, choose the load current line that is closest to
	copper traces. Do not use capacitors larger than 820 µF.
		the current needed in your application, for this example, use
	For additional information, see section on output capaci-	the 3A line. In the maximum input voltage column, select the
	tors in application information section.	line that covers the input voltage needed in your application,
	B. To simplify the capacitor selection procedure, refer to the	in this example, use the 15V line. Continuing on this line are
	quick design component selection table shown in Figure 2.	recommended inductors and capacitors that will provide the
	This table contains different input voltages, output voltages,	best overall performance.
	and load currents, and lists various inductors and output ca-	The capacitor list contains both through hole electrolytic and
	pacitors that will provide the best design solutions.	surface mount tantalum capacitors from four different capaci-
	C. The capacitor voltage rating for electrolytic capacitors	tor manufacturers. It is recommended that both the manufac-
	should be at least 1.5 times greater than the output voltage,	turers and the manufacturer's series that are listed in the
		table be used.
	and often much higher voltage ratings are needed to satisfy
	the low ESR requirements for low output ripple voltage.	In this example aluminum electrolytic capacitors from several
	D. For computer aided design software, see Switchers	different manufacturers are available with the range of ESR
	Made Simple (version 4.2.1 or later).	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 ap-
		proximately 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 volt-
		age by approximately half.

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