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LM2671MX-5.0 [TI]

LM2671 SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage; LM2671 SIMPLE SWITCHER电源转换器高效率路500mA降压电压
LM2671MX-5.0
型号： LM2671MX-5.0
厂家： TEXAS INSTRUMENTS    TEXAS INSTRUMENTS
描述：

LM2671 SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage
LM2671 SIMPLE SWITCHER电源转换器高效率路500mA降压电压

转换器
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LM2671  
www.ti.com  
SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
®
LM2671 SIMPLE SWITCHER Power Converter High Efficiency 500mA Step-Down Voltage  
Regulator with Features  
Check for Samples: LM2671  
1
FEATURES  
234  
•
Efficiency up to 96%  
DESCRIPTION  
The LM2671 series of regulators are monolithic  
integrated circuits built with a LMDMOS process.  
These regulators provide all the active functions for a  
step-down (buck) switching regulator, capable of  
driving a 500mA load current with excellent line and  
load regulation. These devices are available in fixed  
output voltages of 3.3V, 5.0V, 12V, and an adjustable  
output version.  
•
•
Available in SOIC, 8-pin PDIP and WSON  
Packages  
Computer Design Software LM267X Made  
Simple (version 6.0)  
•
•
•
•
Simple and Easy to Design With  
Requires Only 5 external Components  
Uses Readily Available Standard Inductors  
Requiring  
a
minimum number of external  
3.3V, 5.0V, 12V, and Adjustable Output  
Versions  
components, these regulators are simple to use and  
include patented internal frequency compensation  
(Patent Nos. 5,382,918 and 5,514,947), fixed  
frequency oscillator, external shutdown, soft-start,  
and frequency synchronization.  
•
•
Adjustable Version Output Voltage Range:  
1.21V to 37V  
±1.5% Max Output Voltage Tolerance Over  
Line and Load Conditions  
The LM2671 series operates at a switching frequency  
of 260 kHz, thus allowing smaller sized filter  
components than what would be needed with lower  
frequency switching regulators. Because of its very  
high efficiency (>90%), the copper traces on the  
printed circuit board are the only heat sinking needed.  
•
•
•
•
•
Ensured 500mA Output Load Current  
0.25Ω DMOS Output Switch  
Wide Input Voltage Range: 8V to 40V  
260 kHz Fixed Frequency Internal Oscillator  
TTL Shutdown Capability, Low Power Standby  
Mode  
A family of standard inductors for use with the  
LM2671 are available from several different  
manufacturers. This feature greatly simplifies the  
design of switch-mode power supplies using these  
advanced ICs. Also included in the datasheet are  
selector guides for diodes and capacitors designed to  
work in switch-mode power supplies.  
•
•
Soft-Start and Frequency Synchronization  
Thermal Shutdown and Current Limit  
Protection  
APPLICATIONS  
Other features include a ensured ±1.5% tolerance on  
output voltage within specified input voltages and  
output load conditions, and ±10% on the oscillator  
frequency. External shutdown is included, featuring  
typically 50 μA stand-by current. The output switch  
includes current limiting, as well as thermal shutdown  
for full protection under fault conditions.  
•
Simple High Efficiency (>90%) Step-Down  
(Buck) Regulator  
•
Efficient Pre-Regulator for Linear Regulators  
To simplify the LM2671 buck regulator design  
procedure, there exists computer design software,  
LM267X Made Simple (version 6.0).  
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.  
2
3
4
SIMPLE SWITCHER, WEBENCH are registered trademarks of Texas Instruments.  
Windows is a registered trademark of Microsoft Corporation.  
All other trademarks are the property of their respective owners.  
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.  
Copyright © 1998–2013, Texas Instruments Incorporated  
LM2671  
SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
www.ti.com  
Typical Application  
Figure 1. Fixed Output Voltage Versions  
Connection Diagram  
CB  
1
2
3
16  
15  
14  
13  
12  
11  
10  
9
VSW  
VSW  
VIN  
*
*
SS  
DAP**  
4
5
6
7
8
*
GND  
*
SYNC  
GND  
*
FB  
*
ON/OFF  
* No Connections  
**Connect to Pins 11, 12 on PCB  
Figure 2. 16-Lead WSON Surface Mount Package  
Top View  
See Package Drawing Number NHN0016A  
Figure 3. SOIC/PDIP Package  
8-Lead Package  
Top View  
See Package Drawing Number D0008A/P0008E  
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.  
2
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SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
Absolute Maximum Ratings(1)(2)  
Supply Voltage  
45V  
−0.1V ≤ VSH ≤ 6V  
−1V  
ON/OFF Pin Voltage  
Switch Voltage to Ground  
Boost Pin Voltage  
VSW + 8V  
Feedback Pin Voltage  
ESD Susceptibility  
−0.3V ≤ VFB ≤ 14V  
(3)  
Human Body Model  
2 kV  
Internally Limited  
−65°C to +150°C  
Power Dissipation  
Storage Temperature Range  
Lead Temperature  
D Package  
Vapor Phase (60s)  
+215°C  
+220°C  
+260°C  
Infrared (15s)  
P Package (Soldering, 10s)  
WSON Package (See AN-1187)  
Maximum Junction Temperature  
+150°C  
(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 device parameter specifications may not be ensured under these conditions. For  
ensured specifications and test conditions, see the Electrical Characteristics.  
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and  
specifications.  
(3) The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.  
Operating Ratings  
Supply Voltage  
6.5V to 40V  
Temperature Range  
−40°C ≤ TJ ≤ +125°C  
Electrical Characteristics LM2671-3.3  
Specifications with standard type face are for TJ = 25°C, and those in bold type face apply over full Operating Temperature  
Range.  
(2)  
(2)  
Typical  
Min  
Max  
Symbol  
Parameter  
Conditions  
Units  
(1)  
(3)  
SYSTEM PARAMETERS Test Circuit Figure 22  
VOUT  
VOUT  
η
Output Voltage  
Output Voltage  
Efficiency  
VIN = 8V to 40V, ILOAD = 20 mA to 500 mA  
VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA  
VIN = 12V, ILOAD = 500 mA  
3.3  
3.3  
86  
3.251/3.201  
3.251/3.201  
3.350/3.399  
3.350/3.399  
V
V
%
(1) Typical numbers are at 25°C and represent the most likely norm.  
(2) All limits ensured 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 ensured via correlation using standard Statistical Quality Control  
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).  
(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect  
switching regulator performance. When the LM2671 is used as shown in Figure 22 and Figure 23 test circuits, system performance will  
be as specified by the system parameters section of the Electrical Characteristics.  
Copyright © 1998–2013, Texas Instruments Incorporated  
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Units  
Electrical Characteristics LM2671-5.0  
(1)  
(2)  
(2)  
Symbol  
Parameter  
Conditions  
Typical  
Min  
Max  
(3)  
SYSTEM PARAMETERS Test Circuit Figure 22  
VOUT  
VOUT  
η
Output Voltage  
Output Voltage  
Efficiency  
VIN = 8V to 40V, ILOAD = 20 mA to 500 mA  
VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA  
VIN = 12V, ILOAD = 500 mA  
5.0  
5.0  
90  
4.925/4.850  
4.925/4.850  
5.075/5.150  
5.075/5.150  
V
V
%
(1) Typical numbers are at 25°C and represent the most likely norm.  
(2) All limits ensured 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 ensured via correlation using standard Statistical Quality Control  
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).  
(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect  
switching regulator performance. When the LM2671 is used as shown in Figure 22 and Figure 23 test circuits, system performance will  
be as specified by the system parameters section of the Electrical Characteristics.  
Electrical Characteristics LM2671-12  
(1)  
(2)  
(2)  
Symbol  
Parameter  
Conditions  
Typical  
Min  
Max  
Units  
(3)  
SYSTEM PARAMETERS Test Circuit Figure 22  
VOUT  
Output Voltage  
Efficiency  
VIN = 15V to 40V, ILOAD = 20 mA to 500 mA  
VIN = 24V, ILOAD = 500 mA  
12  
94  
11.82/11.64  
12.18/12.36  
V
η
%
(1) Typical numbers are at 25°C and represent the most likely norm.  
(2) All limits ensured 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 ensured via correlation using standard Statistical Quality Control  
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).  
(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect  
switching regulator performance. When the LM2671 is used as shown in Figure 22 and Figure 23 test circuits, system performance will  
be as specified by the system parameters section of the Electrical Characteristics.  
Electrical Characteristics LM2671-ADJ  
(1)  
(2)  
(2)  
Symbol  
Parameter  
Conditions  
Typ  
Min  
Max  
Units  
(3)  
SYSTEM PARAMETERS Test Circuit Figure 23  
VFB  
VFB  
η
Feedback Voltage VIN = 8V to 40V, ILOAD = 20 mA to 500 mA  
VOUT Programmed for 5V  
1.210  
1.192/1.174  
1.192/1.174  
1.228/1.246  
1.228/1.246  
V
(see Circuit of Figure 23)  
Feedback Voltage VIN = 6.5V to 40V, ILOAD = 20 mA to 250 mA  
VOUT Programmed for 5V  
1.210  
90  
V
(see Circuit of Figure 23)  
Efficiency  
VIN = 12V, ILOAD = 500 mA  
%
(1) Typical numbers are at 25°C and represent the most likely norm.  
(2) All limits ensured 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 ensured via correlation using standard Statistical Quality Control  
(SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).  
(3) External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect  
switching regulator performance. When the LM2671 is used as shown in Figure 22 and Figure 23 test circuits, system performance will  
be as specified by the system parameters section of the Electrical Characteristics.  
4
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LM2671  
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SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
All Output Voltage Versions  
Specifications with standard type face are for TJ = 25°C, and those in bold type face apply over full Operating Temperature  
Range. Unless otherwise specified, VIN = 12V for the 3.3V, 5V, and Adjustable versions and VIN = 24V for the 12V version,  
and ILOAD = 100 mA.  
Symbol  
Parameters  
Conditions  
Typ  
Min  
Max  
Units  
DEVICE PARAMETERS  
IQ  
Quiescent Current  
VFEEDBACK = 8V  
For 3.3V, 5.0V, and ADJ Versions  
2.5  
2.5  
3.6  
mA  
mA  
VFEEDBACK = 15V  
For 12V Versions  
ISTBY  
ICL  
Standby Quiescent Current  
Current Limit  
ON/OFF Pin = 0V  
50  
100/150  
1.2/1.25  
μA  
0.8  
0.62/0.575  
A
IL  
Output Leakage Current  
VIN = 40V, ON/OFF Pin = 0V  
VSWITCH = 0V  
1
25  
μA  
VSWITCH = −1V, ON/OFF Pin = 0V  
ISWITCH = 500 mA  
6
0.25  
260  
95  
15  
0.40/0.60  
275  
mA  
Ω
RDS(ON)  
Switch On-Resistance  
Oscillator Frequency  
fO  
D
Measured at Switch Pin  
225  
kHz  
%
Maximum Duty Cycle  
Minimum Duty Cycle  
0
%
IBIAS  
VS/D  
Feedback Bias Current  
ON/OFF Pin Voltage Thesholds  
ON/OFF Pin Current  
VFEEDBACK = 1.3V ADJ Version Only  
85  
nA  
V
1.4  
20  
0.8  
7
2.0  
37  
IS/D  
ON/OFF Pin = 0V  
μA  
kHz  
FSYNC  
VSYNC  
Synchronization Frequency  
VSYNC = 3.5V, 50% duty cycle  
400  
Synchronization Threshold  
Voltage  
1.4  
V
VSS  
ISS  
Soft-Start Voltage  
Soft-Start Current  
Thermal Resistance  
0.63  
4.5  
95  
0.53  
1.5  
0.73  
6.9  
V
μA  
(1)  
θJA  
P Package, Junction to Ambient  
°C/W  
(1)  
D Package, Junction to Ambient  
105  
(1) Junction to ambient thermal resistance with approximately 1 square inch of printed circuit board copper surrounding the leads. Additional  
copper area will lower thermal resistance further. See Application Information section in the application note accompanying this  
datasheet and the thermal model in LM267X Made Simple version 6.0 software. The value θJ−A for the WSON (NHN) package is  
specifically dependent on PCB trace area, trace material, and the number of layers and thermal vias. For improved thermal resistance  
and power dissipation for the WSON package, refer to Application Note AN-1187 SNOA401.  
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Typical Performance Characteristics  
Normalized  
Output Voltage  
Line Regulation  
Figure 4.  
Figure 5.  
Drain-to-Source  
Resistance  
Efficiency  
Figure 6.  
Figure 7.  
Operating  
Quiescent Current  
Switch Current Limit  
Figure 8.  
Figure 9.  
6
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SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
Typical Performance Characteristics (continued)  
Standby  
Quiescent Current  
ON/OFF Threshold  
Voltage  
Figure 10.  
Figure 11.  
ON/OFF Pin  
Current (Sourcing)  
Switching Frequency  
Figure 12.  
Figure 13.  
Feedback Pin  
Bias Current  
Peak Switch Current  
Figure 14.  
Figure 15.  
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Typical Performance Characteristics (continued)  
Dropout Voltage—3.3V Option  
Dropout Voltage—5.0V Option  
Figure 16.  
Figure 17.  
BLOCK DIAGRAM  
* Patent Number 5,514,947  
† Patent Number 5,382,918  
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SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
Typical Performance Characteristics  
(Circuit of Figure 22)  
Continuous Mode Switching Waveforms  
VIN = 20V, VOUT = 5V, ILOAD = 500 mA  
L = 100 μH, COUT = 100 μF, COUTESR = 0.1Ω  
Discontinuous Mode Switching Waveforms  
VIN = 20V, VOUT = 5V, ILOAD = 300 mA  
L = 15 μH, COUT = 68 μF (2×), COUTESR = 25 mΩ  
A: VSW Pin Voltage, 10 V/div.  
B: Inductor Current, 0.2 A/div  
C: Output Ripple Voltage, 50 mV/div AC-Coupled  
A: VSW Pin Voltage, 10 V/div.  
B: Inductor Current, 0.5 A/div  
C: Output Ripple Voltage, 20 mV/div AC-Coupled  
Figure 18. Horizontal Time Base: 1 μs/div  
Figure 19. Horizontal Time Base: 1 μs/div  
Load Transient Response for Continuous Mode  
VIN = 20V, VOUT = 5V  
L = 100 μH, COUT = 100 μF, COUTESR = 0.1Ω  
Load Transient Response for Discontinuous Mode  
VIN = 20V, VOUT = 5V,  
L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ  
A: Output Voltage, 100 mV/div, AC-Coupled  
B: Load Current: 100 mA to 500 mA Load Pulse  
Figure 20. Horizontal Time Base: 50 μs/div  
A: Output Voltage, 100 mV/div, AC-Coupled  
B: Load Current: 100 mA to 400 mA Load Pulse  
Figure 21. Horizontal Time Base: 200 μs/div  
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TEST CIRCUIT AND LAYOUT GUIDELINES  
CIN - 22 μF, 50V Tantalum, Sprague “199D Series”  
COUT - 47 μF, 25V Tantalum, Sprague “595D Series”  
D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F  
L1 - 68 μH Sumida #RCR110D-680L  
CB - 0.01 μF, 50V Ceramic  
Figure 22. Standard Test Circuits and Layout Guides  
Fixed Output Voltage Versions  
CIN - 22 μF, 50V Tantalum, Sprague “199D Series”  
COUT - 47 μF, 25V Tantalum, Sprague “595D Series”  
D1 - 3.3A, 50V Schottky Rectifier, IR 30WQ05F  
L1 - 68 μH Sumida #RCR110D-680L  
R1 - 1.5 kΩ, 1%  
CB - 0.01 μF, 50V Ceramic  
For a 5V output, select R2 to be 4.75 kΩ, 1%  
where VREF = 1.21V  
Use a 1% resistor for best stability.  
Figure 23. Standard Test Circuits and Layout Guides  
Adjustable Output Voltage Versions  
Application Hints  
The LM2671 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  
0.5A, and highly efficient operation.  
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LM2671  
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SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
The LM2671 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 TI's WEBENCH® design tool, a complete switching power supply can be designed quickly.  
Also, refer to the LM2670 data sheet for additional applications information.  
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 the VSW pin cycles 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 the VIN pin. In addition to providing energy to the load the  
input voltage also provides bias for the internal circuitry of the LM2671. For ensured performance the input  
voltage must be in the range of 6.5V to 40V. For best performance of the power supply the VIN pin should always  
be bypassed with an input capacitor located close to this pin and GND.  
C BOOST  
A capacitor must be connected from the CB pin to the VSW pin. 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 LM2671, it is recommended that a broad ground plane be used  
to minimize signal coupling throughout the circuit  
SYNC  
This input allows control of the switching clock frequency. If left open-circuited the regulator will be switched at  
the internal oscillator frequency, typically 260 kHz. An external clock can be used to force the switching  
frequency and thereby control the output ripple frequency of the regulator. This capability provides for consistent  
filtering of the output ripple from system to system as well as precise frequency spectrum positioning of the ripple  
frequency which is often desired in communications and radio applications. This external frequency must be  
greater than the LM2671 internal oscillator frequency, which could be as high as 275 kHz, to prevent an  
erroneous reset of the internal ramp oscillator and PWM control of the power switch. The ramp oscillator is reset  
on the positive going edge of the sync input signal. It is recommended that the external TTL or CMOS compatible  
clock (between 0V and a level greater than 3V) be ac coupled to the SYNC pin through a 100pF capacitor and a  
1KΩ resistor to ground.  
When the SYNC function is used, current limit frequency foldback is not active. Therefore, the device may not be  
fully protected against extreme output short circuit conditions.  
FEEDBACK  
This is the input to a two-stage high gain amplifier, which drives the PWM controller. Connect the FB pin directly  
to the output for proper regulation. 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 LM2671.  
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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ON/OFF  
This input provides an electrical ON/OFF control of the power supply. Connecting this pin to ground or to any  
voltage less than 0.8V will completely turn OFF the regulator. The current drain from the input supply when OFF  
is only 50μA. The ON/OFF input has an internal pull-up current source of approximately 20μA and a protection  
clamp zener diode of 7V to ground. When electrically driving the ON/OFF pin the high voltage level for the ON  
condition should not exceed the 6V absolute maximum limit. When ON/OFF control is not required this pin  
should be left open.  
DAP (WSON PACKAGE)  
The Die Attach Pad (DAP) can and should be connected to the PCB Ground plane/island. For CAD and  
assembly guidelines refer to Application Note SNOA401.  
LM2671 Series Buck Regulator Design Procedure (Fixed Output)  
PROCEDURE (Fixed Output Voltage Version)  
EXAMPLE (Fixed Output Voltage Version)  
To simplify the buck regulator design procedure, Texas Instruments  
is making available computer design software to be used with the  
SIMPLE SWITCHER line of switching regulators.LM267X Made  
Simple (version 6.0) is available on Windows® 3.1, NT, or 95  
operating systems.  
Given:  
Given:  
VOUT = 5V  
VOUT = Regulated Output Voltage (3.3V, 5V, or 12V)  
VIN(max) = Maximum DC Input Voltage  
ILOAD(max) = Maximum Load Current  
VIN(max) = 12V  
ILOAD(max) = 500 mA  
1. Inductor Selection (L1)  
1. Inductor Selection (L1)  
A. Select the correct inductor value selection guide from Figure 24  
and Figure 25 or Figure 26 (output voltages of 3.3V, 5V, or 12V  
respectively). For all other voltages, see the design procedure for the  
adjustable version.  
A. Use the inductor selection guide for the 5V version shown in  
Figure 25.  
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).  
B. From the inductor value selection guide shown in Figure 25, the  
inductance region intersected by the 12V horizontal line and the 500  
mA vertical line is 47 μH, and the inductor code is L13.  
C. Select an appropriate inductor from the four manufacturer's part  
C. The inductance value required is 47 μH. From the table in  
numbers listed in Table 1. Each manufacturer makes a different style Table 1, go to the L13 line and choose an inductor part number from  
of inductor to allow flexibility in meeting various design requirements. any of the four manufacturers shown. (In most instances, both  
Listed below are some of the differentiating characteristics of each  
manufacturer's inductors:  
through hole and surface mount inductors are available.)  
Schott: ferrite EP core inductors; these have very low leakage  
magnetic fields to reduce electro-magnetic interference (EMI) and  
are the lowest power loss inductors  
Renco: ferrite stick core inductors; benefits are typically lowest cost  
inductors and can withstand E•T and transient peak currents above  
rated value. Be aware that these inductors have an external  
magnetic field which may generate more EMI than other types of  
inductors.  
Pulse: powered iron toroid core inductors; these can also be low cost  
and can withstand larger than normal E•T and transient peak  
currents. Toroid inductors have low EMI.  
Coilcraft: ferrite drum core inductors; these are the smallest physical  
size inductors, available only as SMT components. Be aware that  
these inductors also generate EMI—but less than stick inductors.  
Complete specifications for these inductors are available from the  
respective manufacturers. A table listing the manufacturers' phone  
numbers is located in Table 2.  
2. Output Capacitor Selection (COUT  
)
2. Output Capacitor Selection (COUT  
)
A. Select an output capacitor from the output capacitor table in  
A. Use the 5.0V section in the output capacitor table in Table 10.  
Table 10. Using the output voltage and the inductance value found in Choose a capacitor value and voltage rating from the line that  
the inductor selection guide, step 1, locate the appropriate capacitor contains the inductance value of 47 μH. The capacitance and  
value and voltage rating.  
voltage rating values corresponding to the 47 μH inductor are the:  
12  
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PROCEDURE (Fixed Output Voltage Version)  
EXAMPLE (Fixed Output Voltage Version)  
The capacitor list contains through-hole electrolytic capacitors from  
four different capacitor manufacturers and surface mount tantalum  
capacitors from two different capacitor manufacturers. It is  
recommended that both the manufacturers and the manufacturer's  
series that are listed in the table be used. A table listing the  
manufacturers' phone numbers is located in Table 4.  
Surface Mount:  
68 μF/10V Sprague 594D Series.  
100 μF/10V AVX TPS Series.  
Through Hole:  
68 μF/10V Sanyo OS-CON SA Series.  
150 μF/35V Sanyo MV-GX Series.  
150 μF/35V Nichicon PL Series.  
150 μF/35V Panasonic HFQ Series.  
3. Catch Diode Selection (D1)  
3. Catch Diode Selection (D1)  
A. In normal operation, the average current of the catch diode is the A. Refer to the table shown in Table 5. In this example, a 1A, 20V  
load current times the catch diode duty cycle, 1-D (D is the switch  
duty cycle, which is approximately the output voltage divided by the  
input voltage). The largest value of the catch diode average current  
occurs at the maximum load current and maximum input voltage  
(minimum D). For normal operation, the catch diode current rating  
must be at least 1.3 times greater than its maximum average  
current. However, if the power supply design must withstand a  
continuous output short, the diode should have a current rating equal  
to the maximum current limit of the LM2671. The most stressful  
condition for this diode is a shorted output condition.  
Schottky diode will provide the best performance. If the circuit must  
withstand a continuous shorted output, a higher current Schottky  
diode is recommended.  
B. The reverse voltage rating of the diode should be at least 1.25  
times the maximum input voltage.  
C. Because of their fast switching speed and low forward voltage  
drop, Schottky diodes provide the best performance and efficiency.  
This Schottky diode must be located close to the LM2671 using  
short leads and short printed circuit traces.  
4. Input Capacitor (CIN  
A low ESR aluminum or tantalum bypass capacitor is needed  
between the input pin and ground to prevent large voltage transients voltage rating and the RMS current rating. With a maximum input  
from appearing at the input. This capacitor should be located close voltage of 12V, an aluminum electrolytic capacitor with a voltage  
to the IC using short leads. In addition, the RMS current rating of the rating greater than 15V (1.25 × VIN) would be needed. The next  
)
4. Input Capacitor (CIN  
)
The important parameters for the input capacitor are the input  
input capacitor should be selected to be at least ½ the DC load  
current. The capacitor manufacturer data sheet must be checked to  
higher capacitor voltage rating is 16V.  
The RMS current rating requirement for the input capacitor in a buck  
assure that this current rating is not exceeded. The curves shown in regulator is approximately ½ the DC load current. In this example,  
Figure 28 show typical RMS current ratings for several different  
aluminum electrolytic capacitor values. A parallel connection of two  
or more capacitors may be required to increase the total minimum  
RMS current rating to suit the application requirements.  
For an aluminum electrolytic capacitor, the voltage rating should be  
at least 1.25 times the maximum input voltage. Caution must be  
exercised if solid tantalum capacitors are used. The tantalum  
with a 500 mA load, a capacitor with a RMS current rating of at least  
250 mA is needed. The curves shown in Figure 28 can be used to  
select an appropriate input capacitor. From the curves, locate the  
16V line and note which capacitor values have RMS current ratings  
greater than 250 mA.  
For a through hole design, a 100 μF/16V electrolytic capacitor  
(Panasonic HFQ series, Nichicon PL, Sanyo MV-GX series or  
capacitor voltage rating should be twice the maximum input voltage. equivalent) would be adequate. Other types or other manufacturers'  
The tables in Recommended Application Voltage for AVX TPS and  
Sprague 594D Tantalum Chip Capacitors Derated for 85°C. show  
the recommended application voltage for AVX TPS and Sprague  
capacitors can be used provided the RMS ripple current ratings are  
adequate. Additionally, for a complete surface mount design,  
electrolytic capacitors such as the Sanyo CV-C or CV-BS and the  
594D tantalum capacitors. It is also recommended that they be surge Nichicon WF or UR and the NIC Components NACZ series could be  
current tested by the manufacturer. The TPS series available from  
AVX, and the 593D and 594D series from Sprague are all surge  
current tested. Another approach to minimize the surge current  
stresses on the input capacitor is to add a small inductor in series  
with the input supply line.  
considered.  
For surface mount designs, solid tantalum capacitors can be used,  
but caution must be exercised with regard to the capacitor surge  
current rating and voltage rating. In this example, checking  
Recommended Application Voltage for AVX TPS and Sprague 594D  
Tantalum Chip Capacitors Derated for 85°C., and the Sprague 594D  
series datasheet, a Sprague 594D 15 μF, 25V capacitor is adequate.  
Use caution when using ceramic capacitors for input bypassing,  
because it may cause severe ringing at the VIN pin.  
5. Boost Capacitor (CB)  
5. Boost Capacitor (CB)  
This capacitor develops the necessary voltage to turn the switch  
gate on fully. All applications should use a 0.01 μF, 50V ceramic  
capacitor.  
For this application, and all applications, use a 0.01 μF, 50V ceramic  
capacitor.  
6. Soft-Start Capacitor (CSS - optional)  
6. Soft-Start Capacitor (CSS - optional)  
This capacitor controls the rate at which the device starts up. The  
formula for the soft-start capacitor CSS is:  
For this application, selecting a start-up time of 10 ms and using the  
formula for CSS results in a value of:  
(1)  
(2)  
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PROCEDURE (Fixed Output Voltage Version)  
EXAMPLE (Fixed Output Voltage Version)  
where:  
ISS = Soft-Start Current :4.5 μA typical.  
tSS = Soft-Start Time :Selected.  
VSSTH = Soft-Start Threshold Voltage :0.63V typical.  
VOUT = Output Voltage :Selected.  
VSCHOTTKY = Schottky Diode Voltage Drop :0.4V typical.  
VIN = Input Voltage :Selected.  
If this feature is not desired, leave this pin open. With certain  
softstart capacitor values and operating conditions, the LM2671 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.  
7. Frequency Synchronization (optional)  
7. Frequency Synchronization (optional)  
The LM2671 (oscillator) can be synchronized to run with an external For all applications, use a 1 kΩ resistor and a 100 pF capacitor for  
oscillator, using the sync pin (pin 3). By doing so, the LM2671 can  
be operated at higher frequencies than the standard frequency of  
260 kHz. This allows for a reduction in the size of the inductor and  
output capacitor.  
the RC filter.  
As shown in the drawing below, a signal applied to a RC filter at the  
sync pin causes the device to synchronize to the frequency of that  
signal. For a signal with a peak-to-peak amplitude of 3V or greater, a  
1 kΩ resistor and a 100 pF capacitor are suitable values.  
INDUCTOR VALUE SELECTION GUIDES  
(For Continuous Mode Operation)  
Figure 24. LM2671-3.3  
Figure 25. LM2671-5.0  
14  
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Figure 26. LM2671-12  
Figure 27. LM2671-ADJ  
Table 1. Inductor Manufacturers' Part Numbers  
Schott  
Through  
Hole  
Renco  
Pulse Engineering  
Coilcraft  
Surface  
Mount  
Ind.  
Ref.  
Desg.  
Inductan  
ce  
(μH)  
Current  
(A)  
Surface  
Mount  
Through  
Hole  
Surface  
Mount  
Through  
Hole  
Surface  
Mount  
L2  
L3  
150  
100  
68  
0.21  
0.26  
0.32  
0.37  
0.44  
0.52  
0.32  
0.39  
0.48  
0.58  
0.70  
0.83  
0.99  
0.55  
0.66  
0.82  
0.99  
67143920 67144290  
67143930 67144300  
67143940 67144310  
67148310 67148420  
67148320 67148430  
67148330 67148440  
67143960 67144330  
67143970 67144340  
67143980 67144350  
67143990 67144360  
67144000 67144380  
67148340 67148450  
67148350 67148460  
67144040 67144420  
67144050 67144430  
67144060 67144440  
67144070 67144450  
RL-5470-4  
RL-5470-5  
RL1500-150 PE-53802 PE-53802-S DO1608-154  
RL1500-100 PE-53803 PE-53803-S DO1608-104  
RL1500-68 PE-53804 PE-53804-S DO1608-683  
RL1500-47 PE-53805 PE-53805-S DO1608-473  
RL1500-33 PE-53806 PE-53806-S DO1608-333  
RL1500-22 PE-53807 PE-53807-S DO1608-223  
RL1500-220 PE-53809 PE-53809-S DO3308-224  
RL1500-150 PE-53810 PE-53810-S DO3308-154  
RL1500-100 PE-53811 PE-53811-S DO3308-104  
RL1500-68 PE-53812 PE-53812-S DO3308-683  
RL1500-47 PE-53813 PE-53813-S DO3308-473  
RL1500-33 PE-53814 PE-53814-S DO3308-333  
RL1500-22 PE-53815 PE-53815-S DO3308-223  
RL1500-220 PE-53818 PE-53818-S DO3316-224  
RL1500-150 PE-53819 PE-53819-S DO3316-154  
RL1500-100 PE-53820 PE-53820-S DO3316-104  
RL1500-68 PE-53821 PE-53821-S DO3316-683  
L4  
RL-1284-68-43  
RL-1284-47-43  
RL-1284-33-43  
RL-1284-22-43  
RL-5470-3  
L5  
47  
L6  
33  
L7  
22  
L9  
220  
150  
100  
68  
L10  
L11  
L12  
L13  
L14  
L15  
L18  
L19  
L20  
L21  
RL-5470-4  
RL-5470-5  
RL-5470-6  
47  
RL-5470-7  
33  
RL-1284-33-43  
RL-1284-22-43  
RL-5471-2  
22  
220  
150  
100  
68  
RL-5471-3  
RL-5471-4  
RL-5471-5  
Table 2. Inductor Manufacturers' Phone Numbers  
Coilcraft Inc.  
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  
(612) 475-1173  
(612) 475-1786  
Coilcraft Inc., Europe  
Phone  
FAX  
Pulse Engineering Inc.  
Pulse Engineering Inc., Europe  
Renco Electronics Inc.  
Schott Corp.  
Phone  
FAX  
Phone  
FAX  
Phone  
FAX  
Phone  
FAX  
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Table 3. Output Capacitor Table  
Output Capacitor  
Surface Mount  
Through Hole  
Sanyo MV-GX  
Output  
Voltage  
(V)  
Inductance  
Sprague  
594D Series  
(μF/V)  
120/6.3  
120/6.3  
68/10  
AVX TPS  
Series  
(μF/V)  
100/10  
100/10  
100/10  
100/10  
100/10  
100/10  
100/10  
10010  
100/10  
100/10  
100/10  
100/10  
(2×) 68/20  
68/20  
Sanyo OS-CON  
SA Series  
(μF/V)  
100/10  
68/10  
Nichicon  
PL Series  
(μF/V)  
Panasonic  
(μH)  
Series  
(μF/V)  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
120/35  
HFQ Series  
(μF/V)  
22  
33  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
120/35  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
330/35  
220/35  
150/35  
120/35  
120/35  
120/35  
120/35  
47  
68/10  
3.3  
5.0  
68  
120/6.3  
120/6.3  
120/6.3  
100/16  
68/10  
100/10  
100/10  
100/10  
100/10  
68/10  
100  
150  
22  
33  
47  
68/10  
68/10  
68  
100/16  
100/16  
100/16  
120/20  
68/25  
100/10  
100/10  
100/10  
68/20  
100  
150  
22  
33  
68/20  
47  
47/20  
68/20  
47/20  
12  
68  
47/20  
68/20  
47/20  
100  
150  
220  
47/20  
68/20  
47/20  
47/20  
68/20  
47/20  
47/20  
68/20  
47/20  
Table 4. Capacitor Manufacturers' Phone Numbers  
Nichicon Corp.  
Panasonic  
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  
Phone  
FAX  
AVX Corp.  
Phone  
FAX  
Sprague/Vishay  
Sanyo Corp.  
Phone  
FAX  
Phone  
FAX  
Table 5. Schottky Diode Selection Table  
1A Diodes  
3A Diodes  
VR  
Surface  
Through  
Hole  
Surface  
Mount  
SK32  
Through  
Mount  
SK12  
Hole  
20V  
30V  
1N5817  
SR102  
1N5818  
11DQ03  
SR103  
1N5820  
SR302  
1N5821  
31DQ03  
B120  
SK13  
SK33  
B130  
30WQ03F  
MBRS130  
16  
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Table 5. Schottky Diode Selection Table (continued)  
1A Diodes  
3A Diodes  
VR  
Surface  
Mount  
Through  
Hole  
Surface  
Mount  
Through  
Hole  
40V  
SK14  
1N5819  
11DQ04  
SR104  
SK34  
1N5822  
MBR340  
31DQ04  
SR304  
B140  
30BQ040  
30WQ04F  
MBRS340  
MBRD340  
MBRS140  
10BQ040  
10MQ040  
15MQ040  
SK15  
50V  
MBR150  
11DQ05  
SR105  
SK35  
MBR350  
31DQ05  
SR305  
B150  
30WQ05F  
10BQ050  
Table 6. Diode Manufacturers' Phone Numbers  
International Rectifier Corp.  
Motorola, Inc.  
Phone  
FAX  
(310) 322-3331  
(310) 322-3332  
Phone  
FAX  
(800) 521-6274  
(602) 244-6609  
(516) 847-3000  
(516) 847-3236  
(805) 446-4800  
(805) 446-4850  
General Instruments Corp.  
Diodes, Inc.  
Phone  
FAX  
Phone  
FAX  
Figure 28. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)  
Recommended Application Voltage for AVX TPS and Sprague 594D Tantalum Chip Capacitors Derated  
for 85°C.  
Table 7. AVX TPS  
Recommended  
Application Voltage  
Voltage  
Rating  
+85°C Rating  
3.3  
5
6.3  
10  
20  
25  
10  
12  
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Table 7. AVX TPS (continued)  
Recommended  
Voltage  
Application Voltage  
Rating  
+85°C Rating  
Table 8. Sprague 594D  
+85°C Rating  
15  
35  
Recommended  
Application Voltage  
Voltage  
Rating  
2.5  
3.3  
5
4
6.3  
10  
16  
20  
25  
35  
50  
8
12  
18  
24  
29  
LM2671 Series Buck Regulator Design Procedure (Adjustable Output)  
PROCEDURE (Adjustable Output Voltage Version)  
EXAMPLE (Adjustable Output Voltage Version)  
To simplify the buck regulator design procedure, Texas Instrumnets  
is making available computer design software to be used with the  
SIMPLE SWITCHER line of switching regulators.LM267X Made  
Simple is available on (version 6.0) Windows®3.1, NT, or 95  
operating systems.  
Given:  
Given:  
VOUT = 20V  
VOUT = Regulated Output Voltage  
VIN(max) = Maximum Input Voltage  
ILOAD(max) = Maximum Load Current  
F = Switching Frequency (Fixed at a nominal 260 kHz).  
VIN(max) = 28V  
ILOAD(max) = 500 mA  
F = Switching Frequency (Fixed at a nominal 260 kHz).  
1. Programming Output Voltage (Selecting R1 and R2, as shown in 1. Programming Output Voltage (Selecting R1 and R2, as shown in  
Figure 23)  
Figure 23)  
Use the following formula to select the appropriate resistor values.  
Select R1 to be 1 kΩ, 1%. Solve for R2.  
where VREF = 1.21V  
(3)  
(4)  
Select a value for R1 between 240Ω and 1.5 kΩ. The lower resistor  
R2 = 1 kΩ (16.53 − 1) = 15.53 kΩ, closest 1% value is 15.4 kΩ.  
values minimize noise pickup in the sensitive feedback pin. (For the R2 = 15.4 kΩ.  
lowest temperature coefficient and the best stability with time, use  
1% metal film resistors.)  
(5)  
2. Inductor Selection (L1)  
2. Inductor Selection (L1)  
A. Calculate the inductor Volt • microsecond constant E • T (V • μs), A. Calculate the inductor Volt • microsecond constant (E • T),  
from the following formula:  
(6)  
(7)  
where VSAT=internal switch saturation voltage=0.25V and VD = diode  
forward voltage drop = 0.5V  
B. Use the E • T value from the previous formula and match it with  
the E • T number on the vertical axis of the Inductor Value Selection  
Guide shown in Figure 27.  
B. E • T = 21.6 (V • μs)  
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PROCEDURE (Adjustable Output Voltage Version)  
EXAMPLE (Adjustable Output Voltage Version)  
C. On the horizontal axis, select the maximum load current.  
C. ILOAD(max) = 500 mA  
D. Identify the inductance region intersected by the E • T value and  
the Maximum Load Current value. Each region is identified by an  
inductance value and an inductor code (LXX).  
D. From the inductor value selection guide shown in Figure 27, the  
inductance region intersected by the 21.6 (V • μs) horizontal line and  
the 500 mA vertical line is 100 μH, and the inductor code is L20.  
E. Select an appropriate inductor from the four manufacturer's part  
numbers listed in Table 1. For information on the different types of  
inductors, see the inductor selection in the fixed output voltage  
design procedure.  
E. From the table in Table 1, locate line L20, and select an inductor  
part number from the list of manufacturers' part numbers.  
3. Output Capacitor SeIection (COUT  
)
3. Output Capacitor SeIection (COUT)  
A. Select an output capacitor from the capacitor code selection guide A. Use the appropriate row of the capacitor code selection guide, in  
in Table 9. Using the inductance value found in the inductor  
selection guide, step 1, locate the appropriate capacitor code  
corresponding to the desired output voltage.  
Table 9. For this example, use the 15–20V row. The capacitor code  
corresponding to an inductance of 100 μH is C20.  
B. Select an appropriate capacitor value and voltage rating, using  
the capacitor code, from the output capacitor selection table in  
Table 10. There are two solid tantalum (surface mount) capacitor  
manufacturers and four electrolytic (through hole) capacitor  
manufacturers to choose from. It is recommended that both the  
manufacturers and the manufacturer's series that are listed in the  
table be used. A table listing the manufacturers' phone numbers is  
located in Table 4.  
B. From the output capacitor selection table in Table 10, choose a  
capacitor value (and voltage rating) that intersects the capacitor  
code(s) selected in section A, C20.  
The capacitance and voltage rating values corresponding to the  
capacitor code C20 are the:  
Surface Mount:  
33 μF/25V Sprague 594D Series.  
33 μF/25V AVX TPS Series.  
Through Hole:  
33 μF/25V Sanyo OS-CON SC Series.  
120 μF/35V Sanyo MV-GX Series.  
120 μF/35V Nichicon PL Series.  
120 μF/35V Panasonic HFQ Series.  
Other manufacturers or other types of capacitors may also be used,  
provided the capacitor specifications (especially the 100 kHz ESR)  
closely match the characteristics of the capacitors listed in the output  
capacitor table. Refer to the capacitor manufacturers' data sheet for  
this information.  
4. Catch Diode Selection (D1)  
4. Catch Diode Selection (D1)  
A. In normal operation, the average current of the catch diode is the A. Refer to the table shown in Table 5. Schottky diodes provide the  
load current times the catch diode duty cycle, 1-D (D is the switch  
duty cycle, which is approximately VOUT/VIN). The largest value of  
the catch diode average current occurs at the maximum input  
voltage (minimum D). For normal operation, the catch diode current  
rating must be at least 1.3 times greater than its maximum average  
current. However, if the power supply design must withstand a  
continuous output short, the diode should have a current rating  
greater than the maximum current limit of the LM2671. The most  
stressful condition for this diode is a shorted output condition.  
best performance, and in this example a 1A, 40V Schottky diode  
would be a good choice. If the circuit must withstand a continuous  
shorted output, a higher current (at least 1.2A) Schottky diode is  
recommended.  
B. The reverse voltage rating of the diode should be at least 1.25  
times the maximum input voltage.  
C. Because of their fast switching speed and low forward voltage  
drop, Schottky diodes provide the best performance and efficiency.  
The Schottky diode must be located close to the LM2671 using short  
leads and short printed circuit traces.  
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PROCEDURE (Adjustable Output Voltage Version)  
EXAMPLE (Adjustable Output Voltage Version)  
5. Input Capacitor (CIN  
The important parameters for the input capacitor are the input  
between the input pin and ground to prevent large voltage transients voltage rating and the RMS current rating. With a maximum input  
from appearing at the input. This capacitor should be located close voltage of 28V, an aluminum electrolytic capacitor with a voltage  
to the IC using short leads. In addition, the RMS current rating of the rating of at least 35V (1.25 × VIN) would be needed.  
5. Input Capacitor (CIN  
)
)
A low ESR aluminum or tantalum bypass capacitor is needed  
input capacitor should be selected to be at least ½ the DC load  
current. The capacitor manufacturer data sheet must be checked to  
The RMS current rating requirement for the input capacitor in a buck  
regulator is approximately ½ the DC load current. In this example,  
assure that this current rating is not exceeded. The curves shown in with a 500 mA load, a capacitor with a RMS current rating of at least  
Figure 28 show typical RMS current ratings for several different  
aluminum electrolytic capacitor values. A parallel connection of two  
or more capacitors may be required to increase the total minimum  
RMS current rating to suit the application requirements.  
250 mA is needed. The curves shown in Figure 28 can be used to  
select an appropriate input capacitor. From the curves, locate the  
35V line and note which capacitor values have RMS current ratings  
greater than 250 mA.  
For an aluminum electrolytic capacitor, the voltage rating should be  
at least 1.25 times the maximum input voltage. Caution must be  
exercised if solid tantalum capacitors are used. The tantalum  
For a through hole design, a 68 μF/35V electrolytic capacitor  
(Panasonic HFQ series, Nichicon PL, Sanyo MV-GX series or  
equivalent) would be adequate. Other types or other manufacturers'  
capacitor voltage rating should be twice the maximum input voltage. capacitors can be used provided the RMS ripple current ratings are  
The tables in Recommended Application Voltage for AVX TPS and  
Sprague 594D Tantalum Chip Capacitors Derated for 85°C. show  
the recommended application voltage for AVX TPS and Sprague  
adequate. Additionally, for a complete surface mount design,  
electrolytic capacitors such as the Sanyo CV-C or CV-BS and the  
Nichicon WF or UR and the NIC Components NACZ series could be  
594D tantalum capacitors. It is also recommended that they be surge considered.  
current tested by the manufacturer. The TPS series available from  
AVX, and the 593D and 594D series from Sprague are all surge  
current tested. Another approach to minimize the surge current  
stresses on the input capacitor is to add a small inductor in series  
with the input supply line.  
For surface mount designs, solid tantalum capacitors can be used,  
but caution must be exercised with regard to the capacitor surge  
current rating and voltage rating. In this example, checking  
Recommended Application Voltage for AVX TPS and Sprague 594D  
Tantalum Chip Capacitors Derated for 85°C., and the Sprague 594D  
series datasheet, a Sprague 594D 15 μF, 50V capacitor is adequate.  
Use caution when using ceramic capacitors for input bypassing,  
because it may cause severe ringing at the VIN pin.  
6. Boost Capacitor (CB)  
6. Boost Capacitor (CB)  
This capacitor develops the necessary voltage to turn the switch  
gate on fully. All applications should use a 0.01 μF, 50V ceramic  
capacitor.  
For this application, and all applications, use a 0.01 μF, 50V ceramic  
capacitor.  
If the soft-start and frequency synchronization features are desired,  
look at steps 6 and 7 in the fixed output design procedure.  
Table 9. Capacitor Code Selection Guide  
Inductance (μH)  
Case  
Style  
Output  
Voltage (V)  
(1)  
22  
—
33  
—
47  
—
68  
—
100  
C1  
150  
C2  
220  
C3  
SM and TH  
SM and TH  
SM and TH  
SM and TH  
SM and TH  
SM and TH  
SM and TH  
SM and TH  
SM and TH  
SM and TH  
TH  
1.21–2.50  
2.50–3.75  
3.75–5.0  
5.0–6.25  
6.25–7.5  
7.5–10.0  
10.0–12.5  
12.5–15.0  
15.0–20.0  
20.0–30.0  
30.0–37.0  
—
—
—
C1  
C2  
C3  
C3  
—
—
C4  
C5  
C6  
C6  
C6  
—
C4  
C7  
C6  
C6  
C6  
C6  
C8  
C4  
C7  
C6  
C6  
C6  
C6  
C9  
C10  
C11  
C16  
C19  
C22  
C24  
C11  
C12  
C17  
C20  
C22  
C24  
C12  
C12  
C17  
C20  
C22  
C25  
C13  
C13  
C17  
C20  
C22  
C25  
C13  
C13  
C17  
C20  
C22  
C25  
C13  
C13  
C17  
C20  
C22  
C25  
C14  
C15  
C18  
C21  
C23  
(1) SM - Surface Mount, TH - Through Hole  
Table 10. Output Capacitor Selection Table  
Output Capacitor  
Surface Mount  
Sprague  
Through Hole  
Sanyo MV-GX  
Cap.  
Ref.  
Desg.  
#
AVX TPS  
Series  
(μF/V)  
Sanyo OS-CON  
SA Series  
(μF/V)  
Nichicon  
Panasonic  
HFQ Series  
(μF/V)  
594D Series  
(μF/V)  
Series  
(μF/V)  
220/35  
150/35  
PL Series  
(μF/V)  
C1  
C2  
120/6.3  
100/10  
100/10  
100/10  
220/35  
220/35  
120/6.3  
100/10  
150/35  
150/35  
20  
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SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
Table 10. Output Capacitor Selection Table (continued)  
Output Capacitor  
Surface Mount  
Sprague  
Through Hole  
Sanyo MV-GX  
Cap.  
Ref.  
Desg.  
#
AVX TPS  
Series  
(μF/V)  
Sanyo OS-CON  
SA Series  
(μF/V)  
Nichicon  
PL Series  
(μF/V)  
Panasonic  
HFQ Series  
(μF/V)  
594D Series  
(μF/V)  
120/6.3  
68/10  
Series  
(μF/V)  
120/35  
220/35  
150/35  
120/35  
150/35  
330/35  
330/35  
220/35  
150/35  
120/35  
120/35  
220/35  
220/35  
150/35  
120/35  
220/35  
150/35  
120/35  
150/35  
120/35  
220/50  
150/50  
150/50  
C3  
C4  
100/10  
100/10  
100/10  
100/10  
100/10  
100/10  
100/16  
100/16  
100/16  
100/16  
100/16  
100/16  
68/20  
100/35  
68/10  
120/35  
220/35  
150/35  
120/35  
150/35  
330/35  
330/35  
220/35  
150/35  
120/35  
120/35  
220/35  
220/35  
150/35  
120/35  
220/35  
150/35  
120/35  
150/35  
120/35  
100/50  
100/50  
82/50  
120/35  
220/35  
150/35  
120/35  
150/35  
330/35  
330/35  
220/35  
150/35  
120/35  
120/35  
220/35  
220/35  
150/35  
120/35  
220/35  
150/35  
120/35  
150/35  
120/35  
120/50  
120/50  
82/50  
C5  
100/16  
100/16  
68/10  
100/10  
100/10  
68/10  
C6  
C7  
C8  
100/16  
100/16  
100/16  
100/16  
100/16  
100/16  
100/16  
47/20  
100/10  
100/16  
68/16  
C9  
C10  
C11  
C12  
C13  
C14  
C15  
C16  
C17  
C18  
C19  
C20  
C21  
C22  
C23  
C24  
C25  
68/16  
68/16  
100/16  
100/16  
47/20  
47/20  
68/20  
47/20  
47/20  
68/20  
47/20  
(1)  
68/25  
(2×) 33/25  
33/25  
47/25  
(1)  
33/25  
33/25  
(1)  
33/25  
33/25  
33/25  
(2)  
(2)  
(2)  
(2)  
(2)  
33/35  
(2×) 22/25  
33/35  
(2)  
22/35  
(2)  
(2)  
(2)  
(2)  
(2)  
(1) The SC series of Os-Con capacitors (others are SA series)  
(2) The voltage ratings of the surface mount tantalum chip and Os-Con capacitors are too low to work at these voltages.  
Application Information  
TYPICAL SURFACE MOUNT PC BOARD LAYOUT, FIXED OUTPUT (4X SIZE)  
CIN - 15 μF, 25V, Solid Tantalum Sprague, “594D series”  
COUT - 68 μF, 10V, Solid Tantalum Sprague, “594D series”  
D1 - 1A, 40V Schottky Rectifier, Surface Mount  
L1 - 47 μH, L13, Coilcraft DO3308  
CB - 0.01 μF, 50V, Ceramic  
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SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
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TYPICAL SURFACE MOUNT PC BOARD LAYOUT, ADJUSTABLE OUTPUT (4X SIZE)  
CIN - 15 μF, 50V, Solid Tantalum Sprague, “594D series”  
COUT - 33 μF, 25V, Solid Tantalum Sprague, “594D series”  
D1 - 1A, 40V Schottky Rectifier, Surface Mount  
L1 - 100 μH, L20, Coilcraft DO3316  
CB - 0.01 μF, 50V, Ceramic  
R1 - 1k, 1%  
R2 - Use formula in Design Procedure  
Figure 29. PC Board Layout  
Layout is very important in switching regulator designs. 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 (in Figure 22 and Figure 23) 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 IC 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, IC ground path, 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.  
22  
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LM2671  
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SNVS008K –SEPTEMBER 1998–REVISED APRIL 2013  
REVISION HISTORY  
Changes from Revision J (April 2013) to Revision K  
Page  
•
Changed layout of National Data Sheet to TI format .......................................................................................................... 22  
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PACKAGE OPTION ADDENDUM  
www.ti.com  
1-Nov-2013  
PACKAGING INFORMATION  
Orderable Device  
Status Package Type Package Pins Package  
Eco Plan  
Lead/Ball Finish  
MSL Peak Temp  
Op Temp (°C)  
Device Marking  
Samples  
Drawing  
Qty  
1000  
1000  
(1)  
(2)  
(6)  
(3)  
(4/5)  
LM2671LD-ADJ  
NRND  
ACTIVE  
WSON  
WSON  
NHN  
16  
16  
TBD  
Call TI  
CU SN  
Call TI  
-40 to 125  
-40 to 125  
S0008B  
LM2671LD-ADJ/NOPB  
NHN  
Green (RoHS  
& no Sb/Br)  
Level-3-260C-168 HR  
S0008B  
LM2671M-12/NOPB  
LM2671M-3.3/NOPB  
LM2671M-5.0  
ACTIVE  
ACTIVE  
NRND  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
PDIP  
PDIP  
PDIP  
PDIP  
D
D
D
D
D
D
D
D
D
D
D
P
P
P
P
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
95  
95  
Green (RoHS  
& no Sb/Br)  
CU SN  
CU SN  
Level-1-260C-UNLIM  
Level-1-260C-UNLIM  
Call TI  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
-40 to 125  
2671  
M-12  
Green (RoHS  
& no Sb/Br)  
2671  
M3.3  
95  
TBD  
Call TI  
2671  
M5.0  
LM2671M-5.0/NOPB  
LM2671M-ADJ  
ACTIVE  
NRND  
95  
Green (RoHS  
& no Sb/Br)  
SN | CU SN  
Call TI  
Level-1-260C-UNLIM  
Call TI  
2671  
M5.0  
95  
TBD  
2671  
MADJ  
LM2671M-ADJ/NOPB  
LM2671MX-12/NOPB  
LM2671MX-3.3/NOPB  
LM2671MX-5.0  
ACTIVE  
ACTIVE  
ACTIVE  
NRND  
95  
Green (RoHS  
& no Sb/Br)  
SN | CU SN  
CU SN  
Level-1-260C-UNLIM  
Level-1-260C-UNLIM  
Level-1-260C-UNLIM  
Call TI  
2671  
MADJ  
2500  
2500  
2500  
2500  
2500  
40  
Green (RoHS  
& no Sb/Br)  
2671  
M-12  
Green (RoHS  
& no Sb/Br)  
CU SN  
2671  
M3.3  
TBD  
Call TI  
2671  
M5.0  
LM2671MX-5.0/NOPB  
LM2671MX-ADJ/NOPB  
LM2671N-12/NOPB  
LM2671N-3.3/NOPB  
LM2671N-5.0  
ACTIVE  
ACTIVE  
ACTIVE  
ACTIVE  
NRND  
Green (RoHS  
& no Sb/Br)  
SN | CU SN  
SN | CU SN  
CU SN  
Level-1-260C-UNLIM  
Level-1-260C-UNLIM  
Level-1-NA-UNLIM  
Level-1-NA-UNLIM  
Call TI  
2671  
M5.0  
Green (RoHS  
& no Sb/Br)  
2671  
MADJ  
Green (RoHS  
& no Sb/Br)  
LM2671  
N-12  
40  
Green (RoHS  
& no Sb/Br)  
CU SN  
LM2671  
N-3.3  
40  
TBD  
Call TI  
LM2671  
N-5.0  
LM2671N-5.0/NOPB  
ACTIVE  
40  
Green (RoHS  
& no Sb/Br)  
SN | CU SN  
Level-1-NA-UNLIM  
LM2671  
N-5.0  
Addendum-Page 1  
PACKAGE OPTION ADDENDUM  
www.ti.com  
1-Nov-2013  
Orderable Device  
LM2671N-ADJ/NOPB  
Status Package Type Package Pins Package  
Eco Plan  
Lead/Ball Finish  
MSL Peak Temp  
Op Temp (°C)  
Device Marking  
Samples  
Drawing  
Qty  
(1)  
(2)  
(6)  
(3)  
(4/5)  
ACTIVE  
PDIP  
P
8
40  
Green (RoHS  
& no Sb/Br)  
SN | CU SN  
Level-1-NA-UNLIM  
-40 to 125  
LM2671  
N-ADJ  
(1) The marketing status values are defined as follows:  
ACTIVE: Product device recommended for new designs.  
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.  
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.  
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.  
OBSOLETE: TI has discontinued the production of the device.  
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability  
information and additional product content details.  
TBD: The Pb-Free/Green conversion plan has not been defined.  
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that  
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.  
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between  
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.  
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight  
in homogeneous material)  
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.  
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.  
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation  
of the previous line and the two combined represent the entire Device Marking for that device.  
(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish  
value exceeds the maximum column width.  
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information  
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and  
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.  
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.  
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.  
Addendum-Page 2  
PACKAGE MATERIALS INFORMATION  
www.ti.com  
23-Sep-2013  
TAPE AND REEL INFORMATION  
*All dimensions are nominal  
Device  
Package Package Pins  
Type Drawing  
SPQ  
Reel  
Reel  
A0  
B0  
K0  
P1  
W
Pin1  
Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant  
(mm) W1 (mm)  
LM2671LD-ADJ  
LM2671LD-ADJ/NOPB  
LM2671MX-12/NOPB  
LM2671MX-3.3/NOPB  
LM2671MX-5.0  
WSON  
WSON  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
NHN  
NHN  
D
16  
16  
8
1000  
1000  
2500  
2500  
2500  
2500  
2500  
178.0  
178.0  
330.0  
330.0  
330.0  
330.0  
330.0  
12.4  
12.4  
12.4  
12.4  
12.4  
12.4  
12.4  
5.3  
5.3  
6.5  
6.5  
6.5  
6.5  
6.5  
5.3  
5.3  
5.4  
5.4  
5.4  
5.4  
5.4  
1.3  
1.3  
2.0  
2.0  
2.0  
2.0  
2.0  
8.0  
8.0  
8.0  
8.0  
8.0  
8.0  
8.0  
12.0  
12.0  
12.0  
12.0  
12.0  
12.0  
12.0  
Q1  
Q1  
Q1  
Q1  
Q1  
Q1  
Q1  
D
8
D
8
LM2671MX-5.0/NOPB  
LM2671MX-ADJ/NOPB  
D
8
D
8
Pack Materials-Page 1  
PACKAGE MATERIALS INFORMATION  
www.ti.com  
23-Sep-2013  
*All dimensions are nominal  
Device  
Package Type Package Drawing Pins  
SPQ  
Length (mm) Width (mm) Height (mm)  
LM2671LD-ADJ  
LM2671LD-ADJ/NOPB  
LM2671MX-12/NOPB  
LM2671MX-3.3/NOPB  
LM2671MX-5.0  
WSON  
WSON  
SOIC  
SOIC  
SOIC  
SOIC  
SOIC  
NHN  
NHN  
D
16  
16  
8
1000  
1000  
2500  
2500  
2500  
2500  
2500  
210.0  
213.0  
367.0  
367.0  
367.0  
367.0  
367.0  
185.0  
191.0  
367.0  
367.0  
367.0  
367.0  
367.0  
35.0  
55.0  
35.0  
35.0  
35.0  
35.0  
35.0  
D
8
D
8
LM2671MX-5.0/NOPB  
LM2671MX-ADJ/NOPB  
D
8
D
8
Pack Materials-Page 2  
MECHANICAL DATA  
NHN0016A  
LDA16A (REV A)  
www.ti.com  
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supplied at the time of order acknowledgment.  
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