LM2673SX-5.0/NOPB_技术文档

LM2673

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SNVS030N –APRIL 2000–REVISED APRIL 2013

®

LM2673 SIMPLE SWITCHER 3A Step-Down Voltage Regulator with Adjustable Current

Limit

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1

FEATURES

DESCRIPTION

The LM2673 series of regulators are monolithic

integrated circuits which provide all of the active

functions for a step-down (buck) switching regulator

capable of driving up to 3A loads with excellent line

and load regulation characteristics. High efficiency

(>90%) is obtained through the use of a low ON-

resistance DMOS power switch. The series consists

of fixed output voltages of 3.3V, 5V and 12V and an

adjustable output version.

23

•

Efficiency Up to 94%

•

Simple and Easy to Design with (Using Off-

The-Shelf External Components)

•

Resistor Programmable Peak Current Limit

Over a Range of 2A to 5A

•

150 mΩ DMOS Output Switch

3.3V, 5V and 12V Fixed Output and Adjustable

(1.2V to 37V) Versions

The SIMPLE SWITCHER^®concept provides for a

complete design using a minimum number of external

•

±2% Maximum Output Tolerance Over Full

Line and Load Conditions

components.

A

high fixed frequency oscillator

•

Wide Input Voltage Range: 8V to 40V

260 KHz Fixed Frequency Internal Oscillator

Softstart Capability

(260KHz) allows the use of physically smaller sized

components. A family of standard inductors for use

with the LM2673 are available from several

manufacturers to greatly simplify the design process.

−40 to +125°C Operating Junction Temperature

Range

Other features include the ability to reduce the input

surge current at power-ON by adding a softstart

timing capacitor to gradually turn on the regulator.

The LM2673 series also has built in thermal

shutdown and resistor programmable current limit of

the power MOSFET switch to protect the device and

load circuitry under fault conditions. The output

voltage is ensured to a ±2% tolerance. The clock

frequency is controlled to within a ±11% tolerance.

APPLICATIONS

•

Simple to Design, High Efficiency (>90%) Step-

Down Switching Regulators

Efficient System Pre-Regulator for Linear

Voltage Regulators

Battery Chargers

Typical Application

Feedback

0.01 mF

Input

Voltage

V

IN

Boost

Output

LM2673 - 5.0

L

8V to 40V

Voltage

0.47 mF

+

Switch

Output

C

IN

2 x 15 mF/50V

5V/3A

33 mH

+

Softstart

8.2k

Ground

C

OUT

Current

Limit

Adjust

SR305

180 mF/16V

1 nF

37,125

I

=

CL

R

ADJ

1

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

SIMPLE SWITCHER, Switchers Made Simple are registered trademarks of Texas Instruments.

All other trademarks are the property of their respective owners.

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3

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

LM2673

SNVS030N –APRIL 2000–REVISED APRIL 2013

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Connection Diagrams

Figure 1. DDPAK Package (Top View)

See Package Number KTW0007B

Figure 2. TO-220 Package (Top View)

See Package Number NDZ0007B

V_SW

1

14

13

12

11

10

9

*

V_IN

CB

2

3

4

5

6

7

DAP**

*

CURRENT ADJ

GND

FB

SOFTSTART

8

No Connections

*

Connect to Pin 9 on PCB

**

Figure 3. VSON-14 (Top View)

See Package Number NHM0014A

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

Absolute Maximum Ratings⁽¹⁾⁽²⁾

Input Supply Voltage

Softstart Pin Voltage

Switch Voltage to Ground⁽³⁾

Boost Pin Voltage

45V

−0.1V to 6V

−1V to V_IN

V_SW+ 8V

Feedback Pin Voltage

Power Dissipation

ESD⁽⁴⁾

−0.3V to 14V

Internally Limited

2 kV

Storage Temperature Range

Soldering Temperature

−65°C to 150°C

4 sec, 260°C

10 sec, 240°C

75 sec, 219°C

Wave

Infrared

Vapor Phase

(1) Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicate conditions under

which of the device is ensured. Operating Ratings do not imply ensured performance limits. For ensured performance limits and

associated test condition, see the Electrical Characteristics tables.

(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and

specifications.

(3) The absolute maximum specification of the 'Switch Voltage to Ground' applies to DC voltage. An extended negative voltage limit of -8V

applies to a pulse of up to 20 ns, -6V of 60 ns and -3V of up to 100 ns.

(4) ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5 kΩ resistor into each pin.

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Operating Ratings

Supply Voltage

8V to 40V

Junction Temperature Range (T_J)

−40°C to 125°C

Electrical Characteristics

LM2673-3.3

Limits appearing in bold type face apply over the entire junction temperature range of operation, −40°C to 125°C.

Specifications appearing in normal type apply for T_A= T_J= 25°C. R_ADJ= 8.2KΩ

Symbol

V_OUT

η

Parameter

Output Voltage

Efficiency

Conditions

V_IN= 8V to 40V, 100mA ≤ I_OUT≤ 3A

V_IN= 12V, I_LOAD= 3A

Typ⁽¹⁾

Min⁽²⁾

Max⁽²⁾

Units

V

3.3

3.234/3.201

3.366/3.399

86

%

(1) Typical values are determined with T_A= T_J= 25°C and represent the most likely norm.

(2) All limits are ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature

limits are 100% tested during production with T_A= T_J= 25°C. All limits at temperature extremes are ensured via correlation using

standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

LM2673-5.0

Symbol

V_OUT

η

Parameter

Output Voltage

Efficiency

Conditions

V_IN= 8V to 40V, 100mA ≤ I_OUT≤ 3A

V_IN= 12V, I_LOAD= 3A

Typ⁽¹⁾

5.0

Min⁽²⁾

Max⁽²⁾

Units

V

4.900/4.850

5.100/5.150

88

%

(1) Typical values are determined with T_A= T_J= 25°C and represent the most likely norm.

(2) All limits are ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature

limits are 100% tested during production with T_A= T_J= 25°C. All limits at temperature extremes are ensured via correlation using

standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

LM2673-12

Symbol

V_OUT

η

Parameter

Output Voltage

Efficiency

Conditions

V_IN= 15V to 40V, 100mA ≤ I_OUT≤ 3A

V_IN= 24V, I_LOAD= 3A

Typ⁽¹⁾

12

Min⁽²⁾

Max⁽²⁾

Units

V

11.76/11.64

12.24/12.36

94

%

(1) Typical values are determined with T_A= T_J= 25°C and represent the most likely norm.

(2) All limits are ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature

limits are 100% tested during production with T_A= T_J= 25°C. All limits at temperature extremes are ensured via correlation using

standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

LM2673-ADJ

Symbol

Parameter

Conditions

Typ⁽¹⁾

1.21

88

Min⁽²⁾

Max⁽²⁾

Units

V

V_FB

Feedback Voltage V_IN= 8V to 40V, 100mA ≤ I_OUT≤ 3A

1.186/1.174

1.234/1.246

V_OUTProgrammed for 5V

η

Efficiency

V_IN= 12V, I_LOAD= 3A

%

(1) Typical values are determined with T_A= T_J= 25°C and represent the most likely norm.

(2) All limits are ensured at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature

limits are 100% tested during production with T_A= T_J= 25°C. All limits at temperature extremes are ensured via correlation using

standard Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).

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All Output Voltage Versions

Electrical Characteristics

Limits appearing in bold type face apply over the entire junction temperature range of operation, −40°C to 125°C.

Specifications appearing in normal type apply for T_A= T_J= 25°C. Unless otherwise specified, R_ADJ= 8.2KΩ, V_IN=12V for the

3.3V, 5V and Adjustable versions and V_IN=24V for the 12V version.

Symbol

Parameter

Conditions

Typ

Min

Max

Units

DEVICE PARAMETERS

I_Q

Quiescent Current V_FEEDBACK= 8V

4.2

6

mA

For 3.3V, 5.0V, and ADJ Versions

V_FEEDBACK= 15V

For 12V Versions

V_ADJ

Current Limit

Adjust Voltage

1.21

4.5

1.181/1.169

3.8/3.6

1.229/1.246

5.25/5.4

V

A

I_CL

I_L

Current Limit

R_ADJ= 8.2KΩ⁽¹⁾

Output Leakage

Current

V_IN= 40V, Softstart Pin = 0V

V_SWITCH= 0V

V_SWITCH= −1V

mA

1.0

6

1.5

15

R_DS(ON)

Switch On-

Resistance

I_SWITCH= 3A

0.15

0.17/0.29

Ω

f_O

D

Oscillator

Frequency

Measured at Switch Pin

260

225

280

kHz

Duty Cycle

Maximum Duty Cycle

Minimum Duty Cycle

91

0

%

I_BIAS

Feedback Bias

Current

V_FEEDBACK= 1.3V

ADJ Version Only

85

nA

V_SFST

I_SFST

Softstart Threshold

Voltage

0.63

3.7

0.53

0.74

6.9

V

Softstart Pin

Current

Softstart Pin = 0V

μA

θ_JA

θ_JC

θ_JA

θ_JC

θ_JA

Thermal

Resistance

NDZ Package, Junction to Ambient⁽²⁾

NDZ Package, Junction to Ambient⁽³⁾

NDZ Package, Junction to Case

KTW Package, Junction to Ambient⁽⁴⁾

KTW Package, Junction to Ambient⁽⁵⁾

KTW Package, Junction to Ambient⁽⁶⁾

KTW Package, Junction to Case

65

45

2

56

35

26

2

°C/W

++

NHM Package, Junction to Ambient⁽⁷⁾

NHM Package, Junction to Ambient⁽⁸⁾

55

29

°C/W

(1) The peak switch current limit is determined by the following relationship: I_CL=37,125/ R_ADJ

.

(2) Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads in a

socket, or on a PC board with minimum copper area.

(3) Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads

soldered to a PC board containing approximately 4 square inches of (1 oz.) copper area surrounding the leads.

(4) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board area of 0.136 square inches (the

same size as the DDPAK package) of 1 oz. (0.0014 in. thick) copper.

(5) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board area of 0.4896 square inches

(3.6 times the area of the DDPAK package) of 1 oz. (0.0014 in. thick) copper.

(6) Junction to ambient thermal resistance for the 7 lead DDPAK mounted horizontally against a PC board copper area of 1.0064 square

inches (7.4 times the area of the DDPAK package) of 1 oz. (0.0014 in. thick) copper. Additional copper area will reduce thermal

resistance further. See the thermal model in Switchers Made Simple^®software.

(7) Junction to ambient thermal resistance for the 14-lead VSON mounted on a PC board copper area equal to the die attach paddle.

(8) Junction to ambient thermal resistance for the 14-lead VSON mounted on a PC board copper area using 12 vias to a second layer of

copper equal to die attach paddle. Additional copper area will reduce thermal resistance further. For layout recommendations, refer to

Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.

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Typical Performance Characteristics

Normalized Output Voltage

Line Regulation

Figure 4.

Figure 5.

Efficiency vs Input Voltage

Efficiency vs I_LOAD

Figure 6.

Figure 7.

Switch Current Limit

Operating Quiescent Current

Figure 8.

Figure 9.

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Typical Performance Characteristics (continued)

Switching Frequency

Feedback Pin Bias Current

Figure 10.

Figure 11.

Load Transient Response for Continuous Mode

V_IN= 20V, V_OUT= 5V

L = 33 μH, C_OUT= 200 μF, C_OUTESR = 26 mΩ

Load Transient Response for Discontinuous Mode

V_IN= 20V, V_OUT= 5V,

L = 10 μH, C_OUT= 400 μF, C_OUTESR = 13 mΩ

A: Output Voltage, 100 mV//div, AC-Coupled.

B: Load Current: 500 mA to 3A Load Pulse

A: Output Voltage, 100 mV/div, AC-Coupled.

B: Load Current: 200 mA to 3A Load Pulse

Figure 13. Horizontal Time Base: 200 μs/div

Figure 12. Horizontal Time Base: 100 μs/div

Continuous Mode Switching Waveforms

V_IN= 20V, V_OUT= 5V, I_LOAD= 3A

L = 33 μH, C_OUT= 200 μF, C_OUTESR = 26 mΩ

Discontinuous Mode Switching Waveforms

V_IN= 20V, V_OUT= 5V, I_LOAD= 500 mA

L = 10 μH, C_OUT= 400 μF, C_OUTESR = 13 mΩ

A: V_SWPin Voltage, 10 V/div.

B: Inductor Current, 1 A/div

C: Output Ripple Voltage, 20 mV/div AC-Coupled

Figure 14. Horizontal Time Base: 1 μs/div

Figure 15. Horizontal Time Base: 1 μs//iv

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Block Diagram

* Active Inductor Patent Number 5,514,947

† Active Capacitor Patent Number 5,382,918

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APPLICATION HINTS

The LM2673 provides all of the active functions required for a step-down (buck) switching regulator. The internal

power switch is a DMOS power MOSFET to provide power supply designs with high current capability, up to 3A,

and highly efficient operation.

The LM2673 is part of the SIMPLE SWITCHER family of power converters. A complete design uses a minimum

number of external components, which have been pre-determined from a variety of manufacturers. Using either

this data sheet or a design software program called LM267X Made Simple (version 2.0) a complete switching

power supply can be designed quickly. The software is provided free of charge and can be downloaded from

Texas Instrument's Internet site located at www.ti.com.

SWITCH OUTPUT

This is the output of a power MOSFET switch connected directly to the input voltage. The switch provides energy

to an inductor, an output capacitor and the load circuitry under control of an internal pulse-width-modulator

(PWM). The PWM controller is internally clocked by a fixed 260KHz oscillator. In a standard step-down

application the duty cycle (Time ON/Time OFF) of the power switch is proportional to the ratio of the power

supply output voltage to the input voltage. The voltage on pin 1 switches between Vin (switch ON) and below

ground by the voltage drop of the external Schottky diode (switch OFF).

INPUT

The input voltage for the power supply is connected to pin 2. In addition to providing energy to the load the input

voltage also provides bias for the internal circuitry of the LM2673. For ensured performance the input voltage

must be in the range of 8V to 40V. For best performance of the power supply the input pin should always be

bypassed with an input capacitor located close to pin 2.

C BOOST

A capacitor must be connected from pin 3 to the switch output, pin 1. This capacitor boosts the gate drive to the

internal MOSFET above Vin to fully turn it ON. This minimizes conduction losses in the power switch to maintain

high efficiency. The recommended value for C Boost is 0.01μF.

GROUND

This is the ground reference connection for all components in the power supply. In fast-switching, high-current

applications such as those implemented with the LM2673, it is recommended that a broad ground plane be used

to minimize signal coupling throughout the circuit

CURRENT ADJUST

A key feature of the LM2673 is the ability to tailor the peak switch current limit to a level required by a particular

application. This alleviates the need to use external components that must be physically sized to accommodate

current levels (under shorted output conditions for example) that may be much higher than the normal circuit

operating current requirements.

A resistor connected from pin 5 to ground establishes a current (I_{(pin 5)}= 1.2V / R_ADJ) that sets the peak current

through the power switch. The maximum switch current is fixed at a level of 37,125 / R_ADJ

.

FEEDBACK

This is the input to a two-stage high gain amplifier, which drives the PWM controller. It is necessary to connect

pin 6 to the actual output of the power supply to set the dc output voltage. For the fixed output devices (3.3V, 5V

and 12V outputs), a direct wire connection to the output is all that is required as internal gain setting resistors are

provided inside the LM2673. For the adjustable output version two external resistors are required to set the dc

output voltage. For stable operation of the power supply it is important to prevent coupling of any inductor flux to

the feedback input.

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SOFTSTART

A capacitor connected from pin 7 to ground allows for a slow turn-on of the switching regulator. The capacitor

sets a time delay to gradually increase the duty cycle of the internal power switch. This can significantly reduce

the amount of surge current required from the input supply during an abrupt application of the input voltage. If

softstart is not required this pin should be left open circuited. Please see the C_ssSOFTSTART CAPACITOR

section for further information regarding softstart capacitor values.

DAP (VSON PACKAGE)

The Die Attach Pad (DAP) can and should be connected to PCB Ground plane/island. For CAD and assembly

guidelines refer to Application Note AN-1187 at www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.

DESIGN CONSIDERATIONS

Figure 16. Basic Circuit for Fixed Output Voltage Applications

Figure 17. Basic Circuit for Adjustable Output Voltage Applications

Power supply design using the LM2673 is greatly simplified by using recommended external components. A wide

range of inductors, capacitors and Schottky diodes from several manufacturers have been evaluated for use in

designs that cover the full range of capabilities (input voltage, output voltage and load current) of the LM2673. A

simple design procedure using nomographs and component tables provided in this data sheet leads to a working

design with very little effort. Alternatively, the design software, LM267X Made Simple (version 6.0), can also be

used to provide instant component selection, circuit performance calculations for evaluation, a bill of materials

component list and a circuit schematic.

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The individual components from the various manufacturers called out for use are still just a small sample of the

vast array of components available in the industry. While these components are recommended, they are not

exclusively the only components for use in a design. After a close comparison of component specifications,

equivalent devices from other manufacturers could be substituted for use in an application.

Important considerations for each external component and an explanation of how the nomographs and selection

tables were developed follows.

INDUCTOR

The inductor is the key component in a switching regulator. For efficiency the inductor stores energy during the

switch ON time and then transfers energy to the load while the switch is OFF.

Nomographs are used to select the inductance value required for a given set of operating conditions. The

nomographs assume that the circuit is operating in continuous mode (the current flowing through the inductor

never falls to zero). The magnitude of inductance is selected to maintain a maximum ripple current of 30% of the

maximum load current. If the ripple current exceeds this 30% limit the next larger value is selected.

The inductors offered have been specifically manufactured to provide proper operation under all operating

conditions of input and output voltage and load current. Several part types are offered for a given amount of

inductance. Both surface mount and through-hole devices are available. The inductors from each of the three

manufacturers have unique characteristics.

Renco: ferrite stick core inductors; benefits are typically lowest cost and can withstand ripple and transient peak

currents above the rated value. These inductors have an external magnetic field, which may generate EMI.

Pulse Engineering: powdered iron toroid core inductors; these also can withstand higher than rated currents and,

being toroid inductors, will have low EMI.

Coilcraft: ferrite drum core inductors; these are the smallest physical size inductors and are available only as

surface mount components. These inductors also generate EMI but less than stick inductors.

OUTPUT CAPACITOR

The output capacitor acts to smooth the dc output voltage and also provides energy storage. Selection of an

output capacitor, with an associated equivalent series resistance (ESR), impacts both the amount of output ripple

voltage and stability of the control loop.

The output ripple voltage of the power supply is the product of the capacitor ESR and the inductor ripple current.

The capacitor types recommended in the tables were selected for having low ESR ratings.

In addition, both surface mount tantalum capacitors and through-hole aluminum electrolytic capacitors are offered

as solutions.

Impacting frequency stability of the overall control loop, the output capacitance, in conjunction with the inductor,

creates a double pole inside the feedback loop. In addition the capacitance and the ESR value create a zero.

These frequency response effects together with the internal frequency compensation circuitry of the LM2673

modify the gain and phase shift of the closed loop system.

As a general rule for stable switching regulator circuits it is desired to have the unity gain bandwidth of the circuit

to be limited to no more than one-sixth of the controller switching frequency. With the fixed 260KHz switching

frequency of the LM2673, the output capacitor is selected to provide a unity gain bandwidth of 40KHz maximum.

Each recommended capacitor value has been chosen to achieve this result.

In some cases multiple capacitors are required either to reduce the ESR of the output capacitor, to minimize

output ripple (a ripple voltage of 1% of Vout or less is the assumed performance condition), or to increase the

output capacitance to reduce the closed loop unity gain bandwidth (to less than 40KHz). When parallel

combinations of capacitors are required it has been assumed that each capacitor is the exact same part type.

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The RMS current and working voltage (WV) ratings of the output capacitor are also important considerations. In a

typical step-down switching regulator, the inductor ripple current (set to be no more than 30% of the maximum

load current by the inductor selection) is the current that flows through the output capacitor. The capacitor RMS

current rating must be greater than this ripple current. The voltage rating of the output capacitor should be

greater than 1.3 times the maximum output voltage of the power supply. If operation of the system at elevated

temperatures is required, the capacitor voltage rating may be de-rated to less than the nominal room temperature

rating. Careful inspection of the manufacturer's specification for de-rating of working voltage with temperature is

important.

INPUT CAPACITOR

Fast changing currents in high current switching regulators place a significant dynamic load on the unregulated

power source. An input capacitor helps to provide additional current to the power supply as well as smooth out

input voltage variations.

Like the output capacitor, the key specifications for the input capacitor are RMS current rating and working

voltage. The RMS current flowing through the input capacitor is equal to one-half of the maximum dc load current

so the capacitor should be rated to handle this. Paralleling multiple capacitors proportionally increases the

current rating of the total capacitance. The voltage rating should also be selected to be 1.3 times the maximum

input voltage. Depending on the unregulated input power source, under light load conditions the maximum input

voltage could be significantly higher than normal operation and should be considered when selecting an input

capacitor.

The input capacitor should be placed very close to the input pin of the LM2673. Due to relative high current

operation with fast transient changes, the series inductance of input connecting wires or PCB traces can create

ringing signals at the input terminal which could possibly propagate to the output or other parts of the circuitry. It

may be necessary in some designs to add a small valued (0.1μF to 0.47μF) ceramic type capacitor in parallel

with the input capacitor to prevent or minimize any ringing.

CATCH DIODE

When the power switch in the LM2673 turns OFF, the current through the inductor continues to flow. The path for

this current is through the diode connected between the switch output and ground. This forward biased diode

clamps the switch output to a voltage less than ground. This negative voltage must be greater than −1V so a low

voltage drop (particularly at high current levels) Schottky diode is recommended. Total efficiency of the entire

power supply is significantly impacted by the power lost in the output catch diode. The average current through

the catch diode is dependent on the switch duty cycle (D) and is equal to the load current times (1-D). Use of a

diode rated for much higher current than is required by the actual application helps to minimize the voltage drop

and power loss in the diode.

During the switch ON time the diode will be reversed biased by the input voltage. The reverse voltage rating of

the diode should be at least 1.3 times greater than the maximum input voltage.

BOOST CAPACITOR

The boost capacitor creates a voltage used to overdrive the gate of the internal power MOSFET. This improves

efficiency by minimizing the on resistance of the switch and associated power loss. For all applications it is

recommended to use a 0.01μF/50V ceramic capacitor.

R_ADJ, ADJUSTABLE CURRENT LIMIT

A key feature of the LM2673 is the ability to control the peak switch current. Without this feature the peak switch

current would be internally set to 5A or higher to accommodate 3A load current designs. This requires that both

the inductor (which could saturate with excessively high currents) and the catch diode be able to safely handle

up to 5A which would be conducted under load fault conditions.

If an application only requires a load current of 2A or so the peak switch current can be set to a limit just over the

maximum load current with the addition of a single programming resistor. This allows the use of less powerful

and more cost effective inductors and diodes.

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The peak switch current is equal to a factor of 37,125 divided by R_ADJ. A resistance of 8.2KΩ sets the current

limit to typically 4.5A. For predictable control of the current limit it is recommended to keep the peak switch

current greater than 1A. For lower current applications 500mA and 1A switching regulators, the LM2674 and

LM2672, are available.

When the power switch reaches the current limit threshold it is immediately turned OFF and the internal switching

frequency is reduced. This extends the OFF time of the switch to prevent a steady state high current condition.

As the switch current falls below the current limit threshold, the switch will turn back ON. If a load fault continues,

the switch will again exceed the threshold and switch back OFF. This will result in a low duty cycle pulsing of the

power switch to minimize the overall fault condition power dissipation.

C_ssSOFTSTART CAPACITOR

This optional capacitor controls the rate at which the LM2673 starts up at power on. The capacitor is charged

linearly by an internal current source. This voltage ramp gradually increases the duty cycle of the power switch

until it reaches the normal operating duty cycle defined primarily by the ratio of the output voltage to the input

voltage. The softstart turn-on time is programmable by the selection of Css.

The formula for selecting a softstart capacitor is:

where

•

I_SST= Softstart Current, 3.7μA typical

t_SS= Softstart time, from design requirements

V_SST= Softstart Threshold Voltage, 0.63V typical

V_OUT= Output Voltage, from design requirements

V_SCHOTTKY= Schottky Diode Voltage Drop, typically 0.5V

V_IN= Maximum Input Voltage, from design requirements

(1)

If this feature is not desired, leave the Softstart pin (pin 7) open circuited

With certain softstart capacitor values and operating conditions, the LM2673 can exhibit an overshoot on the

output voltage during turn on. Especially when starting up into no load or low load, the softstart function may not

be effective in preventing a larger voltage overshoot on the output. With larger loads or lower input voltages

during startup this effect is minimized. In particular, avoid using softstart capacitors between 0.033µF and 1µF.

ADDITIONAL APPLICATION INFORMATION

When the output voltage is greater than approximately 6V, and the duty cycle at minimum input voltage is greater

than approximately 50%, the designer should exercise caution in selection of the output filter components. When

an application designed to these specific operating conditions is subjected to a current limit fault condition, it may

be possible to observe a large hysteresis in the current limit. This can affect the output voltage of the device until

the load current is reduced sufficiently to allow the current limit protection circuit to reset itself.

Under current limiting conditions, the LM267x is designed to respond in the following manner:

1. At the moment when the inductor current reaches the current limit threshold, the ON-pulse is immediately

terminated. This happens for any application condition.

2. However, the current limit block is also designed to momentarily reduce the duty cycle to below 50% to avoid

subharmonic oscillations, which could cause the inductor to saturate.

3. Thereafter, once the inductor current falls below the current limit threshold, there is a small relaxation time

during which the duty cycle progressively rises back above 50% to the value required to achieve regulation.

If the output capacitance is sufficiently ‘large’, it may be possible that as the output tries to recover, the output

capacitor charging current is large enough to repeatedly re-trigger the current limit circuit before the output has

fully settled. This condition is exacerbated with higher output voltage settings because the energy requirement of

the output capacitor varies as the square of the output voltage (½CV²), thus requiring an increased charging

current.

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A simple test to determine if this condition might exist for a suspect application is to apply a short circuit across

the output of the converter, and then remove the shorted output condition. In an application with properly

selected external components, the output will recover smoothly.

Practical values of external components that have been experimentally found to work well under these specific

operating conditions are C_OUT= 47µF, L = 22µH. It should be noted that even with these components, for a

device’s current limit of I_CLIM, the maximum load current under which the possibility of the large current limit

hysteresis can be minimized is I_CLIM/2. For example, if the input is 24V and the set output voltage is 18V, then for

a desired maximum current of 1.5A, the current limit of the chosen switcher must be confirmed to be at least 3A.

Under extreme over-current or short circuit conditions, the LM267X employs frequency foldback in addition to the

current limit. If the cycle-by-cycle inductor current increases above the current limit threshold (due to short circuit

or inductor saturation for example) the switching frequency will be automatically reduced to protect the IC.

Frequency below 100 KHz is typical for an extreme short circuit condition.

SIMPLE DESIGN PROCEDURE

Using the nomographs and tables in this data sheet (or use the available design software at www.ti.com) a

complete step-down regulator can be designed in a few simple steps.

Step 1: Define the power supply operating conditions:

Required output voltage

Maximum DC input voltage

Maximum output load current

Step 2: Set the output voltage by selecting a fixed output LM2673 (3.3V, 5V or 12V applications) or determine

the required feedback resistors for use with the adjustable LM2673−ADJ

Step 3: Determine the inductor required by using one of the four nomographs, Figure 18 through Figure 21.

Table 1 provides a specific manufacturer and part number for the inductor.

Step 4: Using Table 6 and Table 7 (fixed output voltage) or Table 12 and Table 13 (adjustable output voltage),

determine the output capacitance required for stable operation. Table 3 and Table 13 provide the specific

capacitor type from the manufacturer of choice.

Step 5: Determine an input capacitor from Table 6 and Table 9 for fixed output voltage applications. Use Table 3

or Table 4 to find the specific capacitor type. For adjustable output circuits select a capacitor from Table 3 or

Table 4 with a sufficient working voltage (WV) rating greater than Vin max, and an rms current rating greater than

one-half the maximum load current (2 or more capacitors in parallel may be required).

Step 6: Select a diode from Table 10. The current rating of the diode must be greater than I load max and the

Reverse Voltage rating must be greater than Vin max.

Step 7: Include a 0.01μF/50V capacitor for Cboost in the design and then determine the value of a softstart

capacitor if desired.

Step 8: Define a value for R_ADJto set the peak switch current limit to be at least 20% greater than Iout max to

allow for at least 30% inductor ripple current (±15% of Iout). For designs that must operate over the full

temperature range the switch current limit should be set to at least 50% greater than Iout max (1.5 x I_outmax).

FIXED OUTPUT VOLTAGE DESIGN EXAMPLE

A system logic power supply bus of 3.3V is to be generated from a wall adapter which provides an unregulated

DC voltage of 13V to 16V. The maximum load current is 2.5A. A softstart delay time of 50mS is desired.

Through-hole components are preferred.

Step 1: Operating conditions are:

Vout = 3.3V

Vin max = 16V

Iload max = 2.5A

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Step 2: Select an LM2673T-3.3. The output voltage will have a tolerance of

±2% at room temperature and ±3% over the full operating temperature range.

Step 3: Use the nomograph for the 3.3V device, Figure 18. The intersection of the 16V horizontal line (V_inmax)

and the 2.5A vertical line (I_loadmax) indicates that L33, a 22μH inductor, is required.

From Table 1, L33 in a through-hole component is available from Renco with part number RL-1283-22-43 or part

number PE-53933 from Pulse Engineering.

Step 4: Use Table 6 or Table 7 to determine an output capacitor. With a 3.3V output and a 33μH inductor there

are four through-hole output capacitor solutions with the number of same type capacitors to be paralleled and an

identifying capacitor code given. Table 3 or Table 4 provide the actual capacitor characteristics. Any of the

following choices will work in the circuit:

1 x 220μF/10V Sanyo OS-CON (code C5)

1 x 1000μF/35V Sanyo MV-GX (code C10)

1 x 2200μF/10V Nichicon PL (code C5)

1 x 1000μF/35V Panasonic HFQ (code C7)

Step 5: Use Table 6 or Table 9 to select an input capacitor. With 3.3V output and 22μH there are three through-

hole solutions. These capacitors provide a sufficient voltage rating and an rms current rating greater than 1.25A

(1/2 I_loadmax). Again using Table 3 or Table 4 for specific component characteristics the following choices are

suitable:

1 x 1000μF/63V Sanyo MV-GX (code C14)

1 x 820μF/63V Nichicon PL (code C24)

1 x 560μF/50V Panasonic HFQ (code C13)

Step 6: From Table 10 a 3A or more Schottky diode must be selected. The 20V rated diodes are sufficient for

the application and for through-hole components two part types are suitable:

1N5820

SR302

Step 7: A 0.01μF capacitor will be used for Cboost. For the 50mS softstart delay the following parameters are to

be used:

I_SST: 3.7μA

t_SS: 50mS

V_SST: 0.63V

V_OUT: 3.3V

V_SCHOTTKY: 0.5V

V_IN: 16V

Using Vin max ensures that the softstart delay time will be at least the desired 50mS.

Using the formula for Css a value of 0.148μF is determined to be required. Use of a standard value 0.22μF

capacitor will produce more than sufficient softstart delay.

Step 8: Determine a value for R_ADJto provide a peak switch current limit of at least 2.5A plus 50% or 3.75A.

(2)

Use a value of 10KΩ.

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ADJUSTABLE OUTPUT DESIGN EXAMPLE

In this example it is desired to convert the voltage from a two battery automotive power supply (voltage range of

20V to 28V, typical in large truck applications) to the 14.8VDC alternator supply typically used to power electronic

equipment from single battery 12V vehicle systems. The load current required is 2A maximum. It is also desired

to implement the power supply with all surface mount components. Softstart is not required.

Step 1: Operating conditions are:

Vout = 14.8V

Vin max = 28V

Iload max = 2A

Step 2: Select an LM2673S-ADJ. To set the output voltage to 14.9V two resistors need to be chosen (R1 and R2

in Figure 17). For the adjustable device the output voltage is set by the following relationship:

where

•

V_FBis the feedback voltage of typically 1.21V

(3)

(4)

A recommended value to use for R1 is 1K. In this example then R2 is determined to be:

R2 = 11.23KΩ

The closest standard 1% tolerance value to use is 11.3KΩ

This will set the nominal output voltage to 14.88V which is within 0.5% of the target value.

Step 3: To use the nomograph for the adjustable device, Figure 21, requires a calculation of the inductor

Volt•microsecond constant (E•T expressed in V•μS) from the following formula:

where

•

V_SATis the voltage drop across the internal power switch which is R_ds(ON)times I_load

(5)

In this example this would be typically 0.15Ω x 2A or 0.3V and V_Dis the voltage drop across the forward bisased

Schottky diode, typically 0.5V. The switching frequency of 260KHz is the nominal value to use to estimate the

ON time of the switch during which energy is stored in the inductor.

For this example E•T is found to be:

(6)

(7)

Using Figure 21, the intersection of 27V•μS horizontally and the 2A vertical line (I_loadmax) indicates that L38 , a

68μH inductor, should be used.

From Table 1, L38 in a surface mount component is available from Pulse Engineering with part number PE-

54038S.

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Step 4: Use Table 12 or Table 13 to determine an output capacitor. With a 14.8V output the 12.5 to 15V row is

used and with a 68μH inductor there are three surface mount output capacitor solutions. Table 3 or Table 4

provide the actual capacitor characteristics based on the C Code number. Any of the following choices can be

used:

1 x 33μF/20V AVX TPS (code C6)

1 x 47μF/20V Sprague 594 (code C8)

1 x 47μF/20V Kemet T495 (code C8)

NOTE

When using the adjustable device in low voltage applications (less than 3V output), if the

nomograph, Figure 21, selects an inductance of 22μH or less, Table 12 and Table 13 do

not provide an output capacitor solution. With these conditions the number of output

capacitors required for stable operation becomes impractical. It is recommended to use

either a 33μH or 47μH inductor and the output capacitors from Table 12 or Table 13.

Step 5: An input capacitor for this example will require at least a 35V WV rating with an rms current rating of 1A

(1/2 Iout max). From Table 3 or Table 4 it can be seen that C12, a 33μF/35V capacitor from Sprague, has the

required voltage/current rating of the surface mount components.

Step 6: From Table 10 a 3A Schottky diode must be selected. For surface mount diodes with a margin of safety

on the voltage rating one of five diodes can be used:

SK34

30BQ040

30WQ04F

MBRS340

MBRD340

Step 7: A 0.01μF capacitor will be used for Cboost.

The softstart pin will be left open circuited.

Step 8: Determine a value for R_ADJto provide a peak switch current limit of at least 2A plus 50% or 3A.

(8)

Use a value of 12.4KΩ.

VSON PACKAGE DEVICES

The LM2673 is offered in the 14 lead VSON surface mount package to allow for a significantly decreased

footprint with equivalent power dissipation compared to the DDPAK. For details on mounting and soldering

specifications,

refer

to

Application

Note

AN-1187

at

www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.

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Inductor Selection Guides

For Continuous Mode Operation

Figure 18. LM2673-3.3

Figure 19. LM2673-5.0

Figure 20. LM2673-12

Figure 21. LM2673-ADJ

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Table 1. Inductor Manufacturer Part Numbers

Inductor

Reference

Number

Renco

Pulse Engineering

Coilcraft

Inductance

(µH)

Current

(A)

Through Hole Surface Mount Through Hole Surface Mount Surface Mount

L23

L24

L25

L29

L30

L31

L32

L33

L34

L38

L39

L40

L41

L44

L45

33

22

15

100

68

47

33

22

15

68

47

33

22

68

10

1.35

1.65

2.00

1.41

1.71

2.06

2.46

3.02

3.65

2.97

3.57

4.26

5.22

3.45

4.47

RL-5471-7

RL-1283-22-43

RL-1283-15-43

RL-5471-4

RL1500-33

RL1500-22

RL1500-15

PE-53823

PE-53824

PE-53825

PE-53823S

PE-53824S

PE-53825S

PE-53829S

PE-53830S

PE-53831S

PE-53932S

PE-53933S

PE-53934S

PE-54038S

PE-54039S

PE-54040S

P0841

DO3316-333

DO3316-223

DO3316-153

DO5022P-104

DO5022P-683

DO5022P-473

DO5022P-333

DO5022P-223

DO5022P-153

—

RL-6050-100 PE-53829

RL-5471-5

RL6050-68

PE-53830

PE-53831

PE-53932

PE-53933

PE-53934

PE-54038

PE-54039

PE-54040

PE-54041

PE-54044

—

RL-5471-6

RL6050-47

RL-5471-7

RL6050-33

RL-1283-22-43

RL-1283-15-43

RL-5472-2

RL6050-22

—

RL-5472-3

—

RL-1283-33-43

RL-1283-22-43

RL-5473-3

—

RL-1283-10-43

P0845

DO5022P-103HC

Table 2. Inductor Manufacturer Contact Numbers

Coilcraft

Phone

FAX

(800) 322-2645

(708) 639-1469

+44 1236 730 595

+44 1236 730 627

(619) 674-8100

(619) 674-8262

+353 93 24 107

+353 93 24 459

(800) 645-5828

(516) 586-5562

Coilcraft, Europe

Pulse Engineering

Pulse Engineering, Europe

Renco Electronics

Phone

FAX

Phone

FAX

Phone

FAX

Phone

FAX

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Capacitor Selection Guides

Table 3. Input and Output Capacitor Codes—Surface Mount

Surface Mount

Capacitor

Reference Code

AVX TPS Series

Sprague 594D Series

Kemet T495 Series

C (µF)

330

100

220

47

WV (V)

6.3

10

Irms (A)

1.15

1.1

C (µF)

WV (V)

6.3

10

Irms (A)

C (µF)

100

220

330

100

150

220

33

WV (V)

6.3

10

Irms (A)

C1

C2

120

220

68

1.1

1.4

0.82

1.1

C3

10

1.15

0.89

1.15

0.77

0.94

0.77

0.63

0.66

1.05

1.35

1

1.1

C4

16

150

47

10

1.1

C5

100

33

16

10

1.1

C6

20

100

180

47

16

1.3

10

1.1

C7

68

20

16

1.95

1.15

1.05

1.6

20

0.78

0.94

0.63

0.66

C8

22

25

20

47

20

C9

10

35

33

25

68

20

C10

C11

C12

C13

22

35

68

25

10

35

15

35

0.75

1

22

35

33

35

4.7

50

15

50

0.9

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Table 4. Input and Output Capacitor Codes—Through Hole

Through Hole

Sanyo MV-GX Series Nichicon PL Series

Capacitor

Reference

Code

Sanyo OS-CON SA Series

Panasonic HFQ Series

C (µF)

WV (V)

Irms

(A)

C (µF)

WV (V)

Irms

(A)

C (µF)

WV (V)

Irms

(A)

C (µF)

WV (V)

Irms

(A)

C1

C2

47

6.3

10

16

20

25

1

1000

270

470

560

820

1000

150

470

680

1000

220

470

680

1000

6.3

16

35

63

0.8

0.6

680

820

10

16

25

35

50

63

0.8

82

120

220

330

560

820

1000

2200

56

35

50

63

0.4

0.44

0.76

1.01

1.4

150

330

100

220

33

1.95

2.45

1.87

2.36

0.96

1.92

2.28

2.25

2.09

0.98

1.06

1.28

1.71

2.18

2.36

2.68

0.41

0.55

0.77

1.02

1.22

1.88

0.63

0.79

1.43

2.68

0.82

1.04

1.3

C3

0.75

0.95

1.25

1.3

1000

1200

2200

3300

3900

6800

180

C4

C5

C6

1.62

1.73

2.8

C7

100

150

100

47

0.65

1.3

C8

C9

1.4

0.36

0.5

C10

C11

C12

C13

C14

C15

C16

C17

C18

C19

C20

C21

C22

C23

C24

C25

1.7

270

100

220

470

560

1200

330

1500

0.76

1.2

470

0.92

1.44

1.68

2.22

1.42

2.51

680

1.5

820

1.75

1800

220

560

2200

150

220

330

100

0.75

1.62

2.22

2.51

390

820

1200

Table 5. Capacitor Manufacturer Contact Numbers

Nichicon

Panasonic

AVX

Phone

FAX

(847) 843-7500

(847) 843-2798

(714) 373-7857

(714) 373-7102

(845) 448-9411

(845) 448-1943

(207) 324-4140

(207) 324-7223

(619) 661-6322

(619) 661-1055

(864) 963-6300

(864) 963-6521

Phone

FAX

Phone

FAX

Sprague/Vishay

Sanyo

Phone

FAX

Phone

FAX

Kemet

Phone

FAX

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Table 6. Output Capacitors for Fixed Output Voltage Application—Surface Mount⁽¹⁾⁽²⁾

Surface Mount

Output Voltage

(V)

Inductance (µH)

AVX TPS Series

Sprague 594D Series

Kemet T495 Series

No.

C Code

C2

No.

3

C Code

C1

No.

4

C Code

10

15

22

33

10

15

22

33

47

10

15

22

33

47

68

100

4

3

2

4

3

2

4

3

2

1

C4

C9

C8

C7

C8

C2

3

C1

4

3.3

C2

2

C7

3

C2

2

C6

2

C2

4

C6

4

C2

2

C7

3

5

C2

2

C7

3

C2

2

C3

2

C2

1

C7

2

C5

3

C6

5

C5

2

C7

4

C5

2

C6

3

12

C5

1

C7

2

C4

1

C6

2

C5

1

C5

2

C4

1

C5

1

(1) No. represents the number of identical capacitor types to be connected in parallel

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

Table 7. Output Capacitors for Fixed Output Voltage Application—Through Hole⁽¹⁾⁽²⁾

Through Hole

Output

Voltage (V)

Inductance

(µH)

Sanyo OS-CON SA

Series

Sanyo MV-GX Series

Nichicon PL Series

Panasonic HFQ Series

No.

1

C Code

C3

No.

1

C Code

C10

C5

No.

1

C Code

C6

No.

2

C Code

C6

10

15

22

33

10

15

22

33

47

10

15

22

33

47

68

100

1

C3

1

C6

2

C5

3.3

1

C5

1

C5

1

C7

1

C2

1

C13

C6

1

C5

2

C4

1

2

C5

1

C5

1

C5

1

C6

5

1

C5

1

C5

1

C5

1

C4

1

C5

1

C13

C18

C17

C13

C11

C10

C9

1

C5

1

C4

1

C4

1

2

C3

2

C7

2

C5

1

2

C5

1

C8

1

C5

1

C5

1

C7

1

C5

1

C5

12

1

C7

1

C3

1

C4

1

C7

1

C3

1

C3

1

C7

1

C2

1

C3

1

C7

1

C2

1

C1

(1) No. represents the number of identical capacitor types to be connected in parallel

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

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Table 8. Input Capacitors for Fixed Output Voltage Application—Surface Mount^(1)(2)(3)

Surface Mount

Output Voltage

(V)

Inductance (µH)

AVX TPS Series

Sprague 594D Series

Kemet T495 Series

No.

C Code

C5

No.

1

C Code

C7

No.

2

C Code

C8

10

15

22

33

10

15

22

33

47

10

15

22

33

47

68

100

2

3

See⁽⁴⁾

2

C9

1

C10

C13

C7

3

C10

C12

C8

3.3

See⁽⁴⁾

C5

2

3

2

1

2

C5

1

C7

2

C8

5

3

C10

2

C12

C13

C10

C12

C13

3

C11

C12

C7

See⁽⁴⁾

2

See⁽⁴⁾

C7

2

3

1

2

C7

2

C7

3

C10

2

3

C10

C12

12

3

C10

2

3

See⁽⁴⁾

2

3

2

1

2

(1) Assumes worst case maximum input voltage and load current for a given inductance value

(2) No. represents the number of identical capacitor types to be connected in parallel

(3) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

(4) Check voltage rating of capacitors to be greater than application input voltage.

Table 9. Input Capacitors for Fixed Output Voltage Application—Through Hole^(1)(2)(3)

Through Hole

Output

Voltage (V)

Inductance

(µH)

Sanyo OS-CON SA

Series

Sanyo MV-GX Series

Nichicon PL Series

Panasonic HFQ Series

No.

1

C Code

C7

No.

2

C Code

C4

No.

1

C Code

C5

No.

1

C Code

C6

10

15

22

33

10

15

22

33

47

10

15

22

33

47

68

100

1

C10

1

C10

C14

C12

C4

1

C18

C24

C20

C14

C18

C23

C20

C18

C23

C21

C22

1

C6

3.3

See⁽⁴⁾

1

See⁽⁴⁾

C7

1

C13

C12

C6

1

2

1

C7

2

C4

1

C6

5

See⁽⁴⁾

1

See⁽⁴⁾

C9

1

C10

C14

C12

C10

C13

C12

C11

1

C13

C12

C6

1

C10

1

C6

1

C10

1

C6

12

See⁽⁴⁾

1

C6

1

C13

C12

C11

1

(1) Assumes worst case maximum input voltage and load current for a given inductance value

(2) No. represents the number of identical capacitor types to be connected in parallel

(3) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

(4) Check voltage rating of capacitors to be greater than application input voltage.

22

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SNVS030N –APRIL 2000–REVISED APRIL 2013

Table 10. Schottky Diode Selection Table

Reverse

Voltage (V)

Surface Mount

5A or More

Through Hole

5A or More

3A

20V

30V

40V

SK32

1N5820

SR302

SK33

MBRD835L

1N5821

31DQ03

1N5822

MBR340

31DQ04

SR403

30WQ03F

SK34

MBRB1545CT

6TQ045S

30BQ040

30WQ04F

MBRS340

MBRD340

SK35

MBR745

80SQ045

6TQ045

50V or More

MBR350

31DQ05

SR305

30WQ05F

Table 11. Diode Manufacturer Contact Numbers

International Rectifier

Phone

FAX

(310) 322-3331

(310) 322-3332

(800) 521-6274

(602) 244-6609

(516) 847-3000

(516) 847-3236

(805) 446-4800

(805) 446-4850

Motorola

Phone

FAX

General Semiconductor

Diodes, Inc.

Phone

FAX

Phone

FAX

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SNVS030N –APRIL 2000–REVISED APRIL 2013

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Table 12. Output Capacitors for Adjustable Output Voltage Applications—Surface Mount⁽¹⁾⁽²⁾

Surface Mount

Output Voltage (V)

Inductance (µH)

AVX TPS Series

No. C Code

Sprague 594D Series

Kemet T495 Series

No.

6

4

3

2

3

2

3

2

1

2

1

4

3

2

1

C Code

C2

No.

7

5

4

3

4

3

2

3

2

1

3

2

1

2

1

2

1

2

1

2

1

8

5

4

3

2

C Code

C3

33⁽³⁾

47⁽³⁾

33⁽³⁾

47⁽³⁾

22

7

5

4

3

4

3

2

3

2

1

3

2

1

2

1

2

1

C1

C2

C3

C2

C5

C4

C5

C6

C8

C9

C10

C9

1.21 to 2.50

2.5 to 3.75

C2

C3

C2

C3

C2

C3

C2

C3

3.75 to 5

5 to 6.25

33

C2

C3

47

C2

C3

22

C3

C4

33

C3

C4

47

C3

C4

68

C3

C4

22

C4

33

C3

C4

6.25 to 7.5

7.5 to 10

10 to 12.5

12.5 to 15

15 to 20

47

C4

C6

68

C3

C4

33

C6

C8

47

C6

C8

68

C6

C8

100

33

C5

C8

C6

C8

47

C6

C8

68

C6

C8

100

33

C6

C8

47

C8

68

C8

100

33

C8

C10

C9

C10

C11

C12

47

68

C9

100

33

C9

C11

C12

C13

47

20 to 30

68

100

10

15

22

30 to 37

No Values Available

33

47

68

(1) No. represents the number of identical capacitor types to be connected in parallel

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

(3) Set to a higher value for a practical design solution. See Application Hints section

24

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SNVS030N –APRIL 2000–REVISED APRIL 2013

Table 13. Output Capacitors for Adjustable Output Voltage Applications—Through Hole⁽¹⁾⁽²⁾

Through Hole

Inductance

(µH)

Sanyo OS-CON SA

Series

Output Voltage (V)

Sanyo MV-GX Series

Nichicon PL Series

Panasonic HFQ Series

No.

2

1

C Code

C3

No.

5

4

3

2

3

2

1

C Code

C1

No.

5

3

2

3

2

1

2

1

2

1

C Code

C3

No.

3

2

1

2

1

2

1

C Code

C

33⁽³⁾

47⁽³⁾

33⁽³⁾

47⁽³⁾

22

1.21 to 2.50

2.5 to 3.75

C2

C1

C3

C5

C2

C5

C2

C10

C11

C10

C3

C1

C2

C1

C3

C1

3.75 to 5

5 to 6.25

33

C2

C1

47

C2

C1

C3

22

C5

C6

C3

33

C4

C6

C1

47

C4

C6

C3

68

C4

C6

C1

22

C5

C6

C1

33

C4

C6

C3

6.25 to 7.5

7.5 to 10

10 to 12.5

12.5 to 15

15 to 20

47

C4

C6

C1

68

C4

C2

C1

33

C7

C6

C14

C9

47

C7

C6

68

C7

C2

100

33

C7

C2

C7

C6

47

C7

C2

68

C7

C2

100

33

C7

C2

C9

C10

C7

C15

C16

C20

47

C9

68

C9

100

33

C9

C10

47

C7

68

C7

100

33

C7

47

C7

20 to 30

No Values Available

68

C7

100

10

C7

C12

C11

15

22

30 to 37

No Values Available

33

47

68

(1) No. represents the number of identical capacitor types to be connected in parallel

(2) C Code indicates the Capacitor Reference number in Table 3 and Table 4 for identifying the specific component from the manufacturer.

(3) Set to a higher value for a practical design solution. See Application Hints section

Submit Documentation Feedback

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SNVS030N –APRIL 2000–REVISED APRIL 2013

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REVISION HISTORY

Changes from Revision M (April 2013) to Revision N

Page

•

Changed layout of National Data Sheet to TI format .......................................................................................................... 25

26

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PACKAGE MATERIALS INFORMATION

www.ti.com

11-Oct-2013

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device

Package Package Pins

Type Drawing

SPQ

Reel

A0

B0

K0

P1

W

Pin1

Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant

(mm) W1 (mm)

LM2673SD-12/NOPB

LM2673SD-3.3/NOPB

LM2673SD-5.0/NOPB

LM2673SD-ADJ/NOPB

LM2673SDX-3.3/NOPB

LM2673SDX-5.0/NOPB

VSON

NHM

KTW

14

7

250

178.0

330.0

16.4

24.4

5.3

6.3

1.5

5.0

12.0

16.0

24.0

Q1

Q2

250

2500

500

LM2673SDX-ADJ/NOPB VSON

LM2673SX-12/NOPB

LM2673SX-3.3/NOPB

LM2673SX-5.0

DDPAK/

TO-263

10.75 14.85

DDPAK/

TO-263

KTW

7

500

330.0

24.4

5.0

16.0

24.0

Q2

DDPAK/

TO-263

LM2673SX-5.0/NOPB

LM2673SX-ADJ

DDPAK/

TO-263

DDPAK/

TO-263

LM2673SX-ADJ/NOPB DDPAK/

TO-263

Pack Materials-Page 1

PACKAGE MATERIALS INFORMATION

www.ti.com

11-Oct-2013

*All dimensions are nominal

Device

Package Type Package Drawing Pins

SPQ

Length (mm) Width (mm) Height (mm)

LM2673SD-12/NOPB

LM2673SD-3.3/NOPB

LM2673SD-5.0/NOPB

LM2673SD-ADJ/NOPB

LM2673SDX-3.3/NOPB

LM2673SDX-5.0/NOPB

LM2673SDX-ADJ/NOPB

LM2673SX-12/NOPB

LM2673SX-3.3/NOPB

LM2673SX-5.0

VSON

NHM

KTW

14

7

250

2500

500

210.0

367.0

185.0

367.0

35.0

45.0

VSON

DDPAK/TO-263

7

LM2673SX-5.0/NOPB

LM2673SX-ADJ

7

LM2673SX-ADJ/NOPB

7

Pack Materials-Page 2

MECHANICAL DATA

NDZ0007B

TA07B (Rev E)

www.ti.com

MECHANICAL DATA

NHM0014A

SRC14A (Rev A)

www.ti.com

MECHANICAL DATA

KTW0007B

TS7B (Rev E)

BOTTOM SIDE OF PACKAGE

www.ti.com

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型号：	LM2673SX-5.0/NOPB
厂家：	TEXAS INSTRUMENTS
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LM2673SX-5.0/NOPB [TI]

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