LM2672M-5.0/NOPB [TI]
LM2672 SIMPLE SWITCHER® Power Converter High Efficiency 1-A Step-Down Voltage Regulator with Features;
| 型号： | LM2672M-5.0/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | LM2672 SIMPLE SWITCHER® Power Converter High Efficiency 1-A Step-Down Voltage Regulator with Features 开关 光电二极管 |
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LM2672
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SNVS136K –SEPTEMBER 1998–REVISED APRIL 2013
®
LM2672 SIMPLE SWITCHER Power Converter High Efficiency 1A Step-Down Voltage
Regulator with Features
Check for Samples: LM2672
1
FEATURES
DESCRIPTION
The LM2672 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 1A 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.
234
•
Efficiency up to 96%
•
•
Available in SOIC-8 and 8-pin PDIP 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 LM2672 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.
•
•
•
•
•
Specified 1A 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
LM2672 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
TYPICAL 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 LM2672 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
LM2672
SNVS136K –SEPTEMBER 1998–REVISED APRIL 2013
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Typical Application
(Fixed Output Voltage Versions)
Connection Diagram
Figure 1. 8-Lead Package
SOIC-8/PDIP Package
See Package Drawing Numbers D (R-PDSO-G8)/P (R-PDIP-T8)
Top View
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
See Package Drawing Number NHN0016A
Top View
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.
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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
2 kV
Human Body Model(3)
Power Dissipation
Internally Limited
−65°C to +150°C
Storage Temperature Range
Lead Temperature
D Package
Vapor Phase (60s)
Infrared (15s)
+215°C
+220°C
+260°C
+150°C
PDIP Package (Soldering, 10s)
Maximum Junction Temperature
(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
specific 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
LM2672-3.3 Electrical Characteristics
Specifications with standard type face are for TJ = 25°C, and those in bold type face apply over full Operating Temperature
Range.
Symbol
Parameter
Conditions
Typ(1)
Min(2)
Max(2)
Units
SYSTEM PARAMETERS Test Circuit Figure 22(3)
VOUT
VOUT
η
Output Voltage
Output Voltage
Efficiency
VIN = 8V to 40V, ILOAD = 20 mA to 1A
VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA
VIN = 12V, ILOAD = 1A
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 specified 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 specified 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 LM2672 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.
LM2672-5.0 Electrical Characteristics
Symbol
Parameter
Conditions
Typ(1)
Min(2)
Max(2)
Units
SYSTEM PARAMETERS Test Circuit Figure 22(3)
VOUT
VOUT
η
Output Voltage
Output Voltage
Efficiency
VIN = 8V to 40V, ILOAD = 20 mA to 1A
VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA
VIN = 12V, ILOAD = 1A
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 specified 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 specified 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 LM2672 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.
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Max(2)
Units
LM2672-12 Electrical Characteristics
Symbol
Parameter
Conditions
Typ(1)
Min(2)
SYSTEM PARAMETERS Test Circuit Figure 22(3)
VOUT
Output Voltage
Efficiency
VIN = 15V to 40V, ILOAD = 20 mA to 1A
VIN = 24V, ILOAD = 1A
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 specified 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 specified 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 LM2672 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.
LM2672-ADJ Electrical Characteristics
Symbol
Parameter
Conditions
Typ(1)
Min(2)
Max(2)
Units
SYSTEM PARAMETERS Test Circuit Figure 23(3)
VFB
VFB
η
Feedback Voltage VIN = 8V to 40V, ILOAD = 20 mA to 1A
VOUT Programmed for 5V
1.210
1.192/1.174
1.228/1.246
V
(see Circuit of Figure 23)
Feedback Voltage VIN = 6.5V to 40V, ILOAD = 20 mA to 500 mA
VOUT Programmed for 5V
1.210
90
1.192/1.174
1.228/1.246
V
(see Circuit of Figure 23)
Efficiency
VIN = 12V, ILOAD = 1A
%
(1) Typical numbers are at 25°C and represent the most likely norm.
(2) All limits specified 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 specified 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 LM2672 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.
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
2.5
2.5
Min
Max
Units
DEVICE PARAMETERS
IQ
Quiescent Current
VFEEDBACK = 8V
3.6
mA
For 3.3V, 5.0V, and ADJ Versions
VFEEDBACK = 15V
mA
For 12V Versions
ISTBY
ICL
Standby Quiescent Current
Current Limit
ON/OFF Pin = 0V
50
1.55
1
100/150
2.1/2.2
25
μA
A
1.25/1.2
IL
Output Leakage Current
VIN = 40V, ON/OFF Pin = 0V
VSWITCH = 0V
μA
VSWITCH = −1V, ON/OFF Pin = 0V
ISWITCH = 1A
6
0.25
260
95
15
0.30/0.50
275
mA
Ω
RDS(ON)
Switch On-Resistance
Oscillator Frequency
Maximum Duty Cycle
Minimum Duty Cycle
Feedback Bias
fO
D
Measured at Switch Pin
225
kHz
%
0
%
IBIAS
VFEEDBACK = 1.3V
ADJ Version Only
85
nA
Current
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All Output Voltage Versions (continued)
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
ON/OFF Pin
Conditions
Typ
Min
0.8
Max
2.0
Units
VS/D
1.4
V
Voltage Thesholds
IS/D
ON/OFF Pin Current
Synchronization Frequency
ON/OFF Pin = 0V
20
7
37
μA
FSYNC
VSYNC
VSYNC = 3.5V, 50% duty cycle
400
kHz
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
θJA
PDIP Package, Junction to Ambient(1)
D Package, Junction to Ambient(1)
°C/W
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.
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Typical Performance Characteristics
Normalized Output Voltage
Line Regulation
Figure 3.
Figure 4.
Drain-to-Source
Resistance
Efficiency
Figure 5.
Figure 6.
Switch Current Limit
Operating Quiescent Current
Figure 7.
Figure 8.
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Typical Performance Characteristics (continued)
Standby Quiescent Current
ON/OFF Threshold Voltage
Figure 9.
Figure 10.
ON/OFF Pin Current (Sourcing)
Switching Frequency
Figure 11.
Figure 12.
Feedback Pin Bias Current
Peak Switch Current
Figure 13.
Figure 14.
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Typical Performance Characteristics (continued)
Dropout Voltage—3.3V Option
Dropout Voltage—5.0V Option
Figure 15.
Figure 16.
* Patent Number 5,514,947
† Patent Number 5,382,918
Figure 17. Block Diagram
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Typical Performance Characteristics
(Circuit of Figure 22)
Continuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 1A
L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ
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, 0.5 A/div
A: VSW Pin Voltage, 10 V/div.
B: Inductor Current, 0.5 A/div
C: Output Ripple Voltage, 20 mV/div AC-Coupled
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, ILOAD = 1A
L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ
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
A: Output Voltage, 100 mV/div, AC-Coupled
B: Load Current: 200 mA to 1A Load Pulse
B: Load Current: 100 mA to 300 mA Load Pulse
Figure 20. Horizontal Time Base: 50 μs/div
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
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Applications Hints
The LM2672 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 1A,
and highly efficient operation.
The LM2672 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 LM2672. 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 LM2672, 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 LM2672 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 LM2672.
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 SNAO401 at http://www.ti.com/lit/an/snoa401/snoa401.pdf.
LM2672 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) = 1A
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 1A
vertical line is 33 μH, and the inductor code is L23.
C. Select an appropriate inductor from the four manufacturer's part
C. The inductance value required is 33 μH. From the table in
numbers listed in Table 1. Each manufacturer makes a different style Table 1, go to the L23 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.
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PROCEDURE (Fixed Output Voltage Version)
2. Output Capacitor Selection (COUT
A. Select an output capacitor from the output capacitor table in
EXAMPLE (Fixed Output Voltage Version)
)
2. Output Capacitor Selection (COUT
)
A. Use the 5.0V section in the output capacitor table in Table 3.
Table 3. 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 33 μH. The capacitance and
value and voltage rating.
voltage rating values corresponding to the 33 μH
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.
220 μF/35V Sanyo MV-GX Series.
220 μF/35V Nichicon PL Series.
220 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 LM2672. 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 LM2672 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 1A load, a capacitor with a RMS current rating of at least 500
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 500 mA.
For a through hole design, a 330 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 Table 7 show the recommended application voltage for capacitors can be used provided the RMS ripple current ratings are
AVX TPS and Sprague 594D tantalum capacitors. It is also
adequate. Additionally, for a complete surface mount design,
recommended that they be surge current tested by the manufacturer. electrolytic capacitors such as the Sanyo CV-C or CV-BS and the
The TPS series available from AVX, and the 593D and 594D series Nichicon WF or UR and the NIC Components NACZ series could be
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.
Use caution when using ceramic capacitors for input bypassing,
because it may cause severe ringing at the VIN pin.
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 Table 7,
and the Sprague 594D series datasheet, a Sprague 594D 15 μF,
25V capacitor is adequate.
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.
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PROCEDURE (Fixed Output Voltage Version)
EXAMPLE (Fixed Output Voltage Version)
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)
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 LM2672 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 LM2672 (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 LM2672 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. LM2672-3.3
Figure 25. LM2672-5.0
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Figure 26. LM2672-12
Figure 27. LM2672-ADJ
Table 1. Inductor Manufacturers' Part Numbers
Schott
Renco
Pulse Engineering
Coilcraft
Surface
Ind.
Ref.
Desg.
Inductance Current
Through
Hole
Surface
Mount
Through
Hole
Surface
Mount
Through
Hole
Surface
Mount
(μH)
(A)
Mount
L4
68
47
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
1.17
1.40
1.70
1.00
1.20
1.47
1.78
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
67144080 67144460
67144090 67144470
67148370 67148480
67144110 67144490
67144120 67144500
67144130 67144510
67144140 67144520
RL-1284-68-43
RL-1284-47-43
RL-1284-33-43
RL-1284-22-43
RL-5470-3
RL1500-68 PE-53804 PE-53804-S
RL1500-47 PE-53805 PE-53805-S
RL1500-33 PE-53806 PE-53806-S
RL1500-22 PE-53807 PE-53807-S
RL1500-220 PE-53809 PE-53809-S
RL1500-150 PE-53810 PE-53810-S
RL1500-100 PE-53811 PE-53811-S
RL1500-68 PE-53812 PE-53812-S
RL1500-47 PE-53813 PE-53813-S
RL1500-33 PE-53814 PE-53814-S
RL1500-22 PE-53815 PE-53815-S
RL1500-220 PE-53818 PE-53818-S
RL1500-150 PE-53819 PE-53819-S
RL1500-100 PE-53820 PE-53820-S
RL1500-68 PE-53821 PE-53821-S
DO1608-683
DO1608-473
DO1608-333
DO1608-223
DO3308-224
DO3308-154
DO3308-104
DO3308-683
DO3308-473
DO3308-333
DO3308-223
DO3316-224
DO3316-154
DO3316-104
DO3316-683
DO3316-473
DO3316-333
DO3316-223
DO5022P-224
DO5022P-154
DO5022P-104
DO5022P-683
L5
L6
33
L7
22
L9
220
150
100
68
L10
L11
L12
L13
L14
L15
L18
L19
L20
L21
L22
L23
L24
L27
L28
L29
L30
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
47
RL-5471-6
—
—
—
—
—
—
—
PE-53822 PE-53822-S
PE-53823 PE-53823-S
PE-53824 PE-53824-S
PE-53827 PE-53827-S
PE-53828 PE-53828-S
PE-53829 PE-53829-S
PE-53830 PE-53830-S
33
RL-5471-7
22
RL-1283-22-43
RL-5471-2
220
150
100
68
RL-5471-3
RL-5471-4
RL-5471-5
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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
Pulse Engineering Inc.
Phone
FAX
Phone
FAX
Pulse Engineering Inc.,
Europe
Phone
FAX
Renco Electronics Inc.
Phone
FAX
Schott Corp.
Phone
FAX
Table 3. Output Capacitor Table
Output Capacitor
Surface Mount
Sprague
Through Hole
Sanyo MV-GX
Output
Voltage
(V)
Inductance
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
Nichicon
PL Series
(μF/V)
Panasonic
(μH)
594D Series
(μF/V)
120/6.3
120/6.3
68/10
SA Series
(μF/V)
100/10
68/10
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
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Table 4. Capacitor Manufacturers' Phone Numbers
Phone
FAX
(847) 843-7500
Nichicon Corp.
Panasonic
(847) 843-2798
(714) 373-7857
(714) 373-7102
(803) 448-9411
(803) 448-1943
(207) 324-4140
(207) 324-7223
(619) 661-6322
(619) 661-1055
Phone
FAX
Phone
FAX
AVX Corp.
Phone
FAX
Sprague/Vishay
Sanyo Corp.
Phone
FAX
Table 5. Schottky Diode Selection Table
1A Diodes
3A Diodes
VR
Surface
Mount
SK12
Through
Hole
Surface
Mount
SK32
Through
Hole
20V
30V
1N5817
SR102
1N5818
11DQ03
SR103
1N5819
11DQ04
SR104
1N5820
SR302
1N5821
31DQ03
B120
SK13
SK33
B130
30WQ03F
MBRS130
SK14
40V
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
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Figure 28. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)
Table 7. Recommended Application Voltage for AVX TPS and
Sprague 594D Tantalum Chip Capacitors Derated for 85°C.
Recommended
Application Voltage
Voltage
Rating
+85°C Rating
3.3
5
6.3
10
20
25
35
10
12
15
Table 8. Sprague 594D
Recommended
Application Voltage
Voltage
Rating
+85°C Rating
2.5
3.3
5
4
6.3
10
16
20
25
35
50
8
12
18
24
29
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LM2672 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 Instruments
is making available computer design software to be used with the
SIMPLE SWITCHERline of switching regulators.LM267X Made
Simple version 6.0 is available onWindows3.1, 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) = 1A
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)
C. ILOAD(max) = 1A
C. On the horizontal axis, select the maximum load current.
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 1A vertical line is 68 μH, and the inductor code is L30.
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 L30, 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 68 μH is C20.
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PROCEDURE (Adjustable Output Voltage Version)
EXAMPLE (Adjustable Output Voltage Version)
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 (Table 10).
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 LM2672. 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 2.2A) 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 LM2672 using short
leads and short printed circuit traces.
5. 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 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
)
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
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 1A load, a capacitor with a RMS current rating of at least 500
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.
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 500 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 330 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 Table 7 show the recommended application voltage for adequate. Additionally, for a complete surface mount design,
AVX TPS and Sprague 594D tantalum capacitors. It is also
electrolytic capacitors such as the Sanyo CV-C or CV-BS and the
recommended that they be surge current tested by the manufacturer. Nichicon WF or UR and the NIC Components NACZ series could be
The TPS series available from AVX, and the 593D and 594D series considered.
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.
Use caution when using ceramic capacitors for input bypassing,
because it may cause severe ringing at the VIN pin.
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 Table 7,
and the Sprague 594D series datasheet, a Sprague 594D 15 μF,
50V capacitor is adequate.
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.
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Table 9. Capacitor Code Selection Guide
Inductance (μH)
Case
Output
Voltage (V)
Style(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)
100/10
100/10
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
Sanyo OS-CON
SA Series
(μF/V)
100/10
100/10
100/35
68/10
Nichicon
Panasonic
HFQ Series
(μF/V)
594D Series
(μF/V)
120/6.3
120/6.3
120/6.3
68/10
Series
(μF/V)
220/35
150/35
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
PL Series
(μF/V)
220/35
150/35
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
C1
C2
220/35
150/35
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
C3
C4
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
68/25
(2×) 33/25
33/25
47/25(1)
33/25(1)
33/25(1)
See(2)
See(2)
See(2)
33/25
33/25
33/25
33/35
(2×) 22/25
22/35
33/35
See(2)
See(2)
See(2)
See(2)
See(2)
See(2)
See(2)
See(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.
Copyright © 1998–2013, Texas Instruments Incorporated
Submit Documentation Feedback
21
Product Folder Links: LM2672
LM2672
SNVS136K –SEPTEMBER 1998–REVISED APRIL 2013
www.ti.com
Application Information
TYPICAL SURFACE MOUNT PC BOARD LAYOUT, FIXD OUTPUT (4X SIZE)
CIN - 15 μF, 50V, Solid Tantalum Sprague, “594D series”
COUT - 68 μF, 16V, Solid Tantalum Sprague, “594D series”
D1 - 1A, 40V Schottky Rectifier, Surface Mount
L1 - 33 μH, L23, Coilcraft DO3316
CB - 0.01 μF, 50V, Ceramic
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 - 68 μH, L30, 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.
22
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Copyright © 1998–2013, Texas Instruments Incorporated
Product Folder Links: LM2672
LM2672
www.ti.com
SNVS136K –SEPTEMBER 1998–REVISED APRIL 2013
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.
WSON PACKAGE DEVICES
The LM2672 is offered in the 16 lead WSON surface mount package to allow for increased power dissipation
compared to the SOIC-8 and PDIP.
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
http://www.ti.com/lsds/ti/analog/powermanagement/power_portal.page.
Copyright © 1998–2013, Texas Instruments Incorporated
Submit Documentation Feedback
23
Product Folder Links: LM2672
LM2672
SNVS136K –SEPTEMBER 1998–REVISED APRIL 2013
www.ti.com
REVISION HISTORY
Changes from Revision J (April 2013) to Revision K
Page
•
Changed layout of National Data Sheet to TI format .......................................................................................................... 23
24
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Copyright © 1998–2013, Texas Instruments Incorporated
Product Folder Links: LM2672
PACKAGE OPTION ADDENDUM
www.ti.com
1-Nov-2013
PACKAGING INFORMATION
Orderable Device
LM2672LD-ADJ/NOPB
LM2672M-12
Status Package Type Package Pins Package
Eco Plan
Lead/Ball Finish
MSL Peak Temp
Op Temp (°C)
-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
-40 to 125
-40 to 125
Device Marking
Samples
Drawing
Qty
(1)
(2)
(6)
(3)
(4/5)
ACTIVE
WSON
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
PDIP
NHN
16
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
8
1000
Green (RoHS
& no Sb/Br)
CU SN
Level-3-260C-168 HR
S0004B
NRND
ACTIVE
NRND
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
P
95
95
TBD
Call TI
Call TI
2672
M-12
LM2672M-12/NOPB
LM2672M-3.3
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
Call TI
2672
M-12
95
TBD
Call TI
2672
M3.3
LM2672M-3.3/NOPB
LM2672M-5.0
ACTIVE
NRND
95
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
Call TI
2672
M3.3
95
TBD
Call TI
2672
M5.0
LM2672M-5.0/NOPB
LM2672M-ADJ
ACTIVE
NRND
95
Green (RoHS
& no Sb/Br)
SN | CU SN
Call TI
Level-1-260C-UNLIM
Call TI
2672
M5.0
95
TBD
2672
MADJ
LM2672M-ADJ/NOPB
LM2672MX-12/NOPB
LM2672MX-3.3
ACTIVE
ACTIVE
NRND
95
Green (RoHS
& no Sb/Br)
SN | CU SN
CU SN
Level-1-260C-UNLIM
Level-1-260C-UNLIM
Call TI
2672
MADJ
2500
2500
2500
2500
2500
2500
2500
40
Green (RoHS
& no Sb/Br)
2672
M-12
TBD
Call TI
2672
M3.3
LM2672MX-3.3/NOPB
LM2672MX-5.0
ACTIVE
NRND
Green (RoHS
& no Sb/Br)
CU SN
Level-1-260C-UNLIM
Call TI
2672
M3.3
TBD
Call TI
2672
M5.0
LM2672MX-5.0/NOPB
LM2672MX-ADJ
ACTIVE
NRND
Green (RoHS
& no Sb/Br)
SN | CU SN
Call TI
Level-1-260C-UNLIM
Call TI
2672
M5.0
TBD
2672
MADJ
LM2672MX-ADJ/NOPB
LM2672N-12/NOPB
ACTIVE
ACTIVE
Green (RoHS
& no Sb/Br)
SN | CU SN
SN | CU SN
Level-1-260C-UNLIM
Level-1-NA-UNLIM
2672
MADJ
Green (RoHS
& no Sb/Br)
LM2672
N-12
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
1-Nov-2013
Orderable Device
Status Package Type Package Pins Package
Eco Plan
Lead/Ball Finish
MSL Peak Temp
Op Temp (°C)
-40 to 125
-40 to 125
-40 to 125
-40 to 125
Device Marking
Samples
Drawing
Qty
(1)
(2)
(6)
(3)
(4/5)
LM2672N-3.3/NOPB
LM2672N-5.0/NOPB
LM2672N-ADJ
ACTIVE
PDIP
PDIP
PDIP
PDIP
P
8
8
8
8
40
Green (RoHS
& no Sb/Br)
CU SN
SN | CU SN
Call TI
Level-1-NA-UNLIM
Level-1-NA-UNLIM
Call TI
LM2672
N-3.3
ACTIVE
NRND
P
P
P
40
40
40
Green (RoHS
& no Sb/Br)
LM2672
N-5.0
TBD
LM2672
N-ADJ
LM2672N-ADJ/NOPB
ACTIVE
Green (RoHS
& no Sb/Br)
SN | CU SN
Level-1-NA-UNLIM
LM2672
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
Addendum-Page 2
PACKAGE OPTION ADDENDUM
www.ti.com
1-Nov-2013
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 3
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)
LM2672LD-ADJ/NOPB
LM2672MX-12/NOPB
LM2672MX-3.3
WSON
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
NHN
D
16
8
1000
2500
2500
2500
2500
2500
2500
2500
178.0
330.0
330.0
330.0
330.0
330.0
330.0
330.0
12.4
12.4
12.4
12.4
12.4
12.4
12.4
12.4
5.3
6.5
6.5
6.5
6.5
6.5
6.5
6.5
5.3
5.4
5.4
5.4
5.4
5.4
5.4
5.4
1.3
2.0
2.0
2.0
2.0
2.0
2.0
2.0
8.0
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
12.0
Q1
Q1
Q1
Q1
Q1
Q1
Q1
Q1
D
8
LM2672MX-3.3/NOPB
LM2672MX-5.0
D
8
D
8
LM2672MX-5.0/NOPB
LM2672MX-ADJ
D
8
D
8
LM2672MX-ADJ/NOPB
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)
LM2672LD-ADJ/NOPB
LM2672MX-12/NOPB
LM2672MX-3.3
WSON
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
NHN
D
16
8
1000
2500
2500
2500
2500
2500
2500
2500
213.0
367.0
367.0
367.0
367.0
367.0
367.0
367.0
191.0
367.0
367.0
367.0
367.0
367.0
367.0
367.0
55.0
35.0
35.0
35.0
35.0
35.0
35.0
35.0
D
8
LM2672MX-3.3/NOPB
LM2672MX-5.0
D
8
D
8
LM2672MX-5.0/NOPB
LM2672MX-ADJ
D
8
D
8
LM2672MX-ADJ/NOPB
D
8
Pack Materials-Page 2
MECHANICAL DATA
NHN0016A
LDA16A (REV A)
www.ti.com
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