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LM2674
SNVS007G – SEPTEMBER 1998 – REVISED JUNE 2016
LM2674 SIMPLE SWITCHER® Power Converter High Efficiency
500-mA Step-Down Voltage Regulator
1 Features
3 Description
•
•
The LM2674 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 500-mA load current with excellent line and
load regulation. These devices are available in fixed
output voltages of 3.3 V, 5 V, 12 V, and an adjustable
output version.
1
•
•
•
•
•
•
•
•
•
•
•
•
Efficiency up to 96%
Available in 8-Pin SOIC, PDIP, and 16-Pin WSON
Packages
Simple and Easy to Design With
Requires Only 5 External Components
Uses Readily Available Standard Inductors
3-V, 5-V, 12-V, and Adjustable Output Versions
Adjustable Version Output Voltage Range: 1.21 V
to 37 V
±1.5% Maximum Output Voltage Tolerance Over
Line and Load Conditions
Ensured 500-mA Output Load Current
0.25-Ω DMOS Output Switch
Wide Input Voltage Range: 8 V to 40 V
260-kHz Fixed Frequency Internal Oscillator
TTL Shutdown Capability, Low Power Standby
Mode
Thermal Shutdown and Current Limit Protection
2 Applications
•
•
•
Simple High Efficiency (>90%) Step-Down (Buck)
Regulators
Efficient Preregulator for Linear Regulators
Positive-to-Negative Converters
Requiring a minimum number of external
components, these regulators are simple to use and
include patented internal frequency compensation
and a fixed frequency oscillator.
The LM2674 series operates at a switching frequency
of 260 kHz, thus allowing smaller sized filter
components than what is required 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
required.
A family of standard inductors for use with the
LM2674 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 data sheet are
selector guides for diodes and capacitors designed to
work in switch-mode power supplies.
Device Information(1)
PART NUMBER
LM2674
PACKAGE
BODY SIZE (NOM)
SOIC (8)
4.90 mm × 3.91 mm
PDIP (8)
9.81 mm × 6.35 mm
WSON (16)
5.00 mm × 5.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Typical Application
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM2674
SNVS007G – SEPTEMBER 1998 – REVISED JUNE 2016
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Description (continued).........................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
4
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
4
4
4
4
5
5
5
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics – 3.3-V Version.................
Electrical Characteristics – 5-V Version....................
Electrical Characteristics – 12-V Version..................
Electrical Characteristics – Adjustable Voltage
Version .......................................................................
7.9 Electrical Characteristics – All Output Voltage
Versions .....................................................................
7.10 Typical Characteristics ............................................
8
6
6
7
Detailed Description ............................................ 10
8.1
8.2
8.3
8.4
9
Overview .................................................................
Functional Block Diagram .......................................
Feature Description.................................................
Device Functional Modes........................................
10
10
10
11
Application and Implementation ........................ 12
9.1 Application Information............................................ 12
9.2 Typical Applications ................................................ 13
10 Power Supply Recommendations ..................... 24
11 Layout................................................................... 25
11.1 Layout Guidelines ................................................. 25
11.2 Layout Examples................................................... 25
12 Device and Documentation Support ................. 27
12.1
12.2
12.3
12.4
12.5
12.6
Documentation Support ........................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
27
27
27
27
27
27
13 Mechanical, Packaging, and Orderable
Information ........................................................... 27
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision F (April 2013) to Revision G
Page
•
Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section .................................................................................................. 1
•
Removed all references to Computer Design Software LM267X Made Simple (Version 6.0).............................................. 1
Changes from Revision E (April 2013) to Revision F
•
2
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 25
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5 Description (continued)
Other features include an 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
standby current. The output switch includes current limiting, as well as thermal shutdown for full protection under
fault conditions.
6 Pin Configuration and Functions
D or P Package
8-Pin SOIC or PDIP
Top View
CB
1
NC
2
8
7
NHN Package
16-Pin WSON
Top View
VSW
VIN
NC
3
6
GND
FB
4
5
ON/OFF
CB
1
16
VSW
NC
2
15
VSW
NC
3
14
VIN
NC
4
13
NC
NC
5
12
GND
NC
6
11
GND
NC
7
10
NC
FB
8
9
DAP
ON/OFF
Not to scale
Not to scale
Connect DAP to pin 11 and 12.
Pin Functions
PIN
NAME
I/O
DESCRIPTION
SOIC, PDIP
WSON
CB
1
1
I
Bootstrap capacitor connection for high-side driver. Connect a high-quality, 470-nF
capacitor from CB to VSW Pin.
FB
4
8
I
Feedback sense input pin. Connect to the midpoint of feedback divider to set VOUT
for ADJ version or connect this pin directly to the output capacitor for a fixed output
version.
ON/OFF
5
9
I
Enable input to the voltage regulator. High = ON and low = OFF. Pull this pin high or
float to enable the regulator
VSW
8
15, 16
O
Source pin of the internal high-side FET. This is a switching node. Attached this pin
to an inductor and the cathode of the external diode
GND
6
11, 12
—
Power ground pins. Connect to system ground. Ground pins of CIN and COUT. Path
to CIN must be as short as possible.
VIN
7
14
I
NC
2, 3
2, 3, 4, 5, 6,
7, 10, 13
—
Supply input pin to collector pin of high-side FET. Connect to power supply and
input bypass capacitors CIN. Path from VIN pin to high frequency bypass CIN and
GND must be as short as possible.
No connect pins
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2)
MIN
MAX
UNIT
45
V
Supply voltage
ON/OFF pin voltage, VSH
–0.1
6
V
–1
V
VSW + 8
V
14
V
Switch voltage to ground
Boost pin voltage
Feedback pin voltage, VFB
–0.3
Power dissipation
Internally Limited
D package
Lead temperature
Vapor phase (60 s)
215
Infrared (15 s)
220
P package (soldering, 10 s)
WSON package
See AN-1187
Maximum junction temperature
Storage temperature, Tstg
(1)
(2)
°C
260
–65
150
°C
150
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
7.2 ESD Ratings
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) (2)
VALUE
UNIT
±2000
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
The human-body model is a 100-pF capacitor discharged through a 1.5-kΩ resistor into each pin.
7.3 Recommended Operating Conditions
MIN
MAX
Supply voltage
6.5
40
UNIT
V
Junction temperature, TJ
–40
125
°C
7.4 Thermal Information
LM2674
THERMAL METRIC
RθJA
(1)
(2)
4
(1)
Junction-to-ambient thermal resistance (2)
D (SOIC)
P (PDIP)
NHN (WSON)
8 PINS
8 PINS
16 PINS
105
95
—
UNIT
°C/W
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
Junction to ambient thermal resistance with approximately 1 square inch of printed-circuit board copper surrounding the leads. Additional
copper area lowers thermal resistance further. The value RθJA 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, see AN-1187 Leadless Leadframe Package (LLP).
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7.5 Electrical Characteristics – 3.3-V Version
TJ = 25°C (unless otherwise noted)
PARAMETER
SYSTEM PARAMETERS (see Figure 15)
Output voltage
VIN = 6.5 V to 40 V, ILOAD = 20 mA to 250 mA
Efficiency
η
(1)
(2)
(3)
MAX (1)
UNIT
(3)
VIN = 8 V to 40 V, ILOAD = 20 mA to 500 mA
VOUT
MIN (1) TYP (2)
TEST CONDITIONS
TJ = 25°C
3.251
TJ = –40°C to 125°C
3.201
TJ = 25°C
3.251
TJ = –40°C to 125°C
3.201
VIN = 12 V, ILOAD = 500 mA
3.3
3.35
3.399
3.3
3.35
V
3.399
86%
All limits are used to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator performance. When the LM2674 is used as shown in Figure 15 and Figure 19, system performance is as specified
by the system parameters section of the Electrical Characteristics.
7.6 Electrical Characteristics – 5-V Version
TJ = 25°C (unless otherwise noted)
PARAMETER
TEST CONDITIONS
SYSTEM PARAMETERS (see Figure 15)
VIN = 8 V to 40 V, ILOAD = 20 mA to 500 mA
VOUT
Output voltage
VIN = 6.5 V to 40 V, ILOAD = 20 mA to 250 mA
Efficiency
η
(1)
(2)
(3)
MIN (1)
TYP (2)
MAX (1)
4.925
5
5.075
5
5.075
UNIT
(3)
TJ = 25°C
TJ = –40°C to 125°C
TJ = 25°C
TJ = –40°C to 125°C
4.85
4.925
5.15
4.85
VIN = 12 V, ILOAD = 500 mA
V
5.15
90%
All limits are used to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator performance. When the LM2674 is used as shown in Figure 15 and Figure 19, system performance is as specified
by the system parameters section of the Electrical Characteristics.
7.7 Electrical Characteristics – 12-V Version
TJ = 25°C (unless otherwise noted)
PARAMETER
SYSTEM PARAMETERS (see Figure 15)
VOUT
Output voltage
VIN = 15 V to 40 V, ILOAD = 20 mA to 500 mA
η
Efficiency
VIN = 24 V, ILOAD = 500 mA
(1)
(2)
(3)
MIN (1)
TYP (2)
MAX (1)
TJ = 25°C
11.82
12
12.18
TJ = –40°C to 125°C
11.64
TEST CONDITIONS
UNIT
(3)
12.36
V
94%
All limits are used to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator performance. When the LM2674 is used as shown in Figure 15 and Figure 19, system performance is as specified
by the system parameters section of the Electrical Characteristics.
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7.8 Electrical Characteristics – Adjustable Voltage Version
TJ = 25°C (unless otherwise noted)
MIN (1)
TYP (2)
MAX (1)
TJ = 25°C
1.192
1.21
1.228
TJ = –40°C to 125°C
1.174
VIN = 6.5 V to 40 V, ILOAD = 20 mA to 250 mA, TJ = 25°C
VOUT programmed for 5 V (see Figure 19)
TJ = –40°C to 125°C
1.192
PARAMETER
TEST CONDITIONS
SYSTEM PARAMETERS (see Figure 19)
VIN = 8 V to 40 V, ILOAD = 20 mA to 500 mA,
VOUT programmed for 5 V (see Figure 19)
VFB
Feedback voltage
η
Efficiency
(1)
(2)
(3)
UNIT
(3)
1.246
1.21
1.174
VIN = 12 V, ILOAD = 500 mA
V
1.228
1.246
90%
All limits are used to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator performance. When the LM2674 is used as shown in Figure 15 and Figure 19, system performance is as specified
by the system parameters section of the Electrical Characteristics.
7.9 Electrical Characteristics – All Output Voltage Versions
TJ = 25°C, VIN = 12 V for the 3.3-V, 5-V, and adjustable versions and VIN = 24 V for the 12-V version, and ILOAD = 100 mA
(unless otherwise noted)
PARAMETERS
TEST CONDITIONS
MIN
TYP
MAX
VFEEDBACK = 8 V for 3.3-V, 5-V, and adjustable
voltage versions
2.5
3.6
VFEEDBACK = 15 V for 12-V versions
2.5
UNIT
DEVICE PARAMETERS
IQ
Quiescent current
ISTBY
Standby quiescent current
ICL
Current limit
IL
Output leakage current
ON/OFF pin = 0 V
1
TJ = 25°C
μA
6
15
mA
0.25
0.4
Ω
TJ = –40°C to 125°C
0.6
TJ = 25°C
260
TJ = –40°C to 125°C
225
VFEEDBACK = 1.3 V (adjustable version only)
IS/D
ON/OFF pin current
ON/OFF pin = 0 V
kHz
275
0%
Turnon threshold, rising (1)
85
TJ = 25°C
nA
1.4
TJ = –40°C to 125°C
0.8
TJ = 25°C
2
20
TJ = –40°C to 125°C
A
25
Minimum duty cycle
Feedback bias current
1.2
μA
1.25
95%
ON/OFF pin voltage threshold
6
0.8
Maximum duty cycle
VS/D
(1)
0.62
0.575
VSWITCH = −1 V, ON/OFF pin = 0 V
Measured at switch pin
mA
100
150
VIN = 40 V, ON/OFF pin = 0 V, VSWITCH = 0 V
fO
IBIAS
TJ = –40°C to 125°C
TJ = –40°C to 125°C
ISWITCH = 500 mA
D
50
TJ = 25°C
RDS(ON) Switch ON-resistance
Oscillator frequency
TJ = 25°C
mA
7
37
V
μA
The ON/OFF pin is internally pulled up to 7 V and can be left floating for always-on operation.
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7.10 Typical Characteristics
Figure 1. Normalized Output Voltage
Figure 2. Line Regulation
Figure 3. Efficiency
Figure 4. Drain-to-Source Resistance
Figure 5. Switch Current Limit
Figure 6. Operating Quiescent Current
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Typical Characteristics (continued)
8
Figure 7. Standby Quiescent Current
Figure 8. ON/OFF Threshold Voltage
Figure 9. ON/OFF Pin Current (Sourcing)
Figure 10. Switching Frequency
Figure 11. Feedback Pin Bias Current
Figure 12. Peak Switch Current
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Typical Characteristics (continued)
Figure 13. Dropout Voltage, 3.3-V Version
Figure 14. Dropout Voltage, 5-V Version
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8 Detailed Description
8.1 Overview
The LM2674 SIMPLE SWITCHER® regulator is an easy-to-use non-synchronous step-down DC-DC converter
with a wide input voltage range up to 40 V. It is capable of delivering up to 0.5-A DC load current with excellent
line and load regulation. These devices are available in fixed output voltages of 3.3 V, 5 V, 12 V, and an
adjustable output version. The family requires few external components and the pin arrangement was designed
for simple, optimum PCB layout.
8.2 Functional Block Diagram
8.3 Feature Description
8.3.1 Adjustable Output Voltage
The voltage regulation loop in the LM2674 regulates output voltage by maintaining the voltage on FB pin (VFB)
to be the same as the internal REF voltage (VREF). A resistor divider pair is required to program the ratio from
output voltage VOUT to VFB. The resistor is connected from the VOUT of the LM2674 to ground with the midpoint connecting to the FB pin. The voltage reference system produces a precise voltage reference over
temperature. The internal REF voltage is 1.21 V typically. To program the output voltage of the LM2674 to be a
certain value VOUT, R1 can be calculated with a selected R2 (see Adjustable Output Voltage Typical
Application). R2 is in the range from 10 kΩ to 100 kΩ is recommended for most applications. If the resistor
10
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Feature Description (continued)
divider is not connected properly, output voltage cannot be regulated because the feedback loop is broken. If the
FB pin is shorted to ground, the output voltage is driven close to VIN, because the regulator sees very low
voltage on the FB pin and tries to regulator it up. The load connected to the output could be damaged under
such a condition. Do not short FB pin to ground when the LM2674 is enabled. It is important to route the
feedback trace away from the noisy area of the PCB. For more layout recommendations, see Layout.
8.4 Device Functional Modes
8.4.1 Shutdown Mode
The ON/OFF pin provides electrical ON and OFF control for the LM2674. When the voltage of this pin is lower
than 1.4 V, the device is in shutdown mode. The typical standby current in this mode is 50 μA.
8.4.2 Active Mode
When the voltage of the ON/OFF pin is higher than 1.4 V, the device starts switching and the output voltage rises
until it reaches a normal regulation voltage.
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The LM2674 is a step-down DC-DC regulator. It is typically used to convert a higher DC voltage to a lower DC
voltage with a maximum output current of 0.5 A. The following design procedure can be used to select
components for the LM2674. Alternately, the WEBENCH® software may be used to generate complete designs.
When generating a design, the WEBENCH software uses iterative design procedure and accesses
comprehensive databases of components. See ti.com for more details.
When the output voltage is greater than approximately 6 V, and the duty cycle at minimum input voltage is
greater than approximately 50%, the designer must exercise caution in selection of the output filter components.
When an application designed to these specific operating conditions is subjected to a current limit fault condition,
it may be possible to observe a large hysteresis in the current limit. This can affect the output voltage of the
device until the load current is reduced sufficiently to allow the current limit protection circuit to reset itself.
Under current limiting conditions, the LM267x is designed to respond in the following manner:
1. At the moment when the inductor current reaches the current limit threshold, the ON-pulse is immediately
terminated. This happens for any application condition.
2. However, the current limit block is also designed to momentarily reduce the duty cycle to below 50% to avoid
subharmonic oscillations, which could cause the inductor to saturate.
3. Thereafter, once the inductor current falls below the current limit threshold, there is a small relaxation time
during which the duty cycle progressively rises back above 50% to the value required to achieve regulation.
If the output capacitance is sufficiently large, it may be possible that as the output tries to recover, the output
capacitor charging current is large enough to repeatedly re-trigger the current limit circuit before the output has
fully settled. This condition is exacerbated with higher output voltage settings because the energy requirement of
the output capacitor varies as the square of the output voltage (½ CV2), thus requiring an increased charging
current. A simple test to determine if this condition might exist for a suspect application is to apply a short circuit
across the output of the converter, and then remove the shorted output condition. In an application with properly
selected external components, the output recovers smoothly. Practical values of external components that have
been experimentally found to work well under these specific operating conditions are COUT = 47 µF, L = 22 µH.
NOTE
Even with these components, for a device’s current limit of ICLIM, the maximum load
current under which the possibility of the large current limit hysteresis can be minimized is
ICLIM/2.
For example, if the input is 24 V and the set output voltage is 18 V, then for a desired maximum current of 1.5 A,
the current limit of the chosen switcher must be confirmed to be at least 3 A. Under extreme overcurrent or shortcircuit conditions, the LM267X employs frequency foldback in addition to the current limit. If the cycle-by-cycle
inductor current increases above the current limit threshold (due to short circuit or inductor saturation for
example) the switching frequency is automatically reduced to protect the IC. Frequency below 100 kHz is typical
for an extreme short-circuit condition.
12
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9.2 Typical Applications
9.2.1 Fixed Output Voltage Typical Application
CIN = 22-μF, 50-V Tantalum, Sprague 199D Series
COUT = 47-μF, 25-V Tantalum, Sprague 595D Series
D1 = 3.3-A, 50-V Schottky Rectifier, IR 30WQ05F
L1 = 68-μH Sumida #RCR110D-680L
CB = 0.01-μF, 50-V Ceramic
Figure 15. Fixed Output Voltage Version
9.2.1.1 Design Requirements
Table 1 lists the design parameters of this example.
Table 1. Design Parameters
PARAMETER
VALUE
Regulated output voltage (3.3 V, 5 V, or 12 V), VOUT
5V
Maximum DC input voltage, VIN(max)
12 V
Maximum load current, ILOAD(max)
500 mA
9.2.1.2 Detailed Design Procedure
9.2.1.2.1 Inductor Selection (L1)
1. Select the correct inductor value selection guide from Figure 24, Figure 25, or Figure 26 (output voltages of
3.3 V, 5 V, or 12 V respectively). For all other voltages, see the design procedure for the adjustable version.
Use the inductor selection guide for the 5-V version shown in Figure 25.
2. 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). From the inductor value selection guide shown in Figure 25, the inductance region
intersected by the 12-V horizontal line and the 500-mA vertical line is 47 μH, and the inductor code is L13.
3. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 7. Each
manufacturer makes a different style of inductor to allow flexibility in meeting various design requirements.
Listed below are some of the differentiating characteristics of each manufacturer's inductors:
– 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
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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. The inductance
value required is 47 μH. From Table 7, go to the L13 line and choose an inductor part number from any of the
four manufacturers shown. (In most instances, both through hole and surface mount inductors are available).
9.2.1.2.2 Output Capacitor Selection (COUT)
Select an output capacitor from the output capacitor Table 2. Using the output voltage and the inductance value
found in the inductor selection guide, step 1, locate the appropriate capacitor value and voltage rating. Use the
5-V section in the output capacitor Table 2. Choose a capacitor value and voltage rating from the line that
contains the inductance value of 47 μH. The capacitance and voltage rating values corresponding to the 47-μH
inductor are the following:
• Surface mount
– 68-μF, 10-V Sprague 594D series
– 100-μF, 10-V AVX TPS series
• Through hole
– 68-μF, 10-V Sanyo OS-CON SA series
– 150-μF, 35-V Sanyo MV-GX series
– 150-μF, 35-V Nichicon PL series
– 150-μF, 35-V Panasonic HFQ series
The capacitor list contains through-hole electrolytic capacitors from four different capacitor manufacturers and
surface-mount tantalum capacitors from two different capacitor manufacturers. TI recommends that both the
manufacturers and the manufacturer's series that are listed in the table be used.
Table 2. Output Capacitor Table
OUTPUT CAPACITOR
OUTPUT
VOLTAGE
(V)
3.3
5
12
14
INDUCTANCE
(μH)
SURFACE MOUNT
THROUGH HOLE
SPRAGUE
594D SERIES
(μF/V)
AVX TPS
SERIES
(μF/V)
SANYO OS-CON
SA SERIES (μF/V)
SANYO MV-GX
SERIES (μF/V)
NICHICON
PL SERIES
(μF/V)
PANASONIC
HFQ SERIES
(μF/V)
22
120/6.3
100/10
100/10
330/35
330/35
330/35
33
120/6.3
100/10
68/10
220/35
220/35
220/35
47
68/10
100/10
68/10
150/35
150/35
150/35
68
120/6.3
100/10
100/10
120/35
120/35
120/35
100
120/6.3
100/10
100/10
120/35
120/35
120/35
150
120/6.3
100/10
100/10
120/35
120/35
120/35
22
100/16
100/10
100/10
330/35
330/35
330/35
33
68/10
10010
68/10
220/35
220/35
220/35
47
68/10
100/10
68/10
150/35
150/35
150/35
68
100/16
100/10
100/10
120/35
120/35
120/35
100
100/16
100/10
100/10
120/35
120/35
120/35
150
100/16
100/10
100/10
120/35
120/35
120/35
22
120/20
(2×) 68/20
68/20
330/35
330/35
330/35
33
68/25
68/20
68/20
220/35
220/35
220/35
47
47/20
68/20
47/20
150/35
150/35
150/35
68
47/20
68/20
47/20
120/35
120/35
120/35
100
47/20
68/20
47/20
120/35
120/35
120/35
150
47/20
68/20
47/20
120/35
120/35
120/35
220
47/20
68/20
47/20
120/35
120/35
120/35
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9.2.1.2.3 Catch Diode Selection (D1)
1. In normal operation, the average current of the catch diode is the 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 must have a current rating equal to the maximum current limit of the LM2674. The
most stressful condition for this diode is a shorted output condition. Refer to Table 3. In this example, a 1-A,
20-V Schottky diode provides the best performance. If the circuit must withstand a continuous shorted output,
a higher current Schottky diode is recommended.
Table 3. Schottky Diode Selection Table
500-mA DIODES
3-A DIODES
VR
SURFACE
MOUNT
THROUGHHOLE
SURFACE
MOUNT
THROUGHHOLE
20V
SK12
1N5817
SK32
1N5820
B120
SR102
30V
SK13
1N5818
SK33
1N5821
B130
11DQ03
30WQ03F
31DQ03
40V
SR302
MBRS130
SR103
SK14
1N5819
SK34
1N5822
B140
11DQ04
30BQ040
MBR340
MBRS140
SR104
30WQ04F
31DQ04
10BQ040
MBRS340
SR304
10MQ040
MBRD340
15MQ040
50V
SK15
MBR150
SK35
MBR350
B150
11DQ05
30WQ05F
31DQ05
10BQ050
SR105
SR305
2. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage.
3. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best
performance and efficiency. This Schottky diode must be placed close to the LM2674 using short leads and
short printed-circuit traces.
9.2.1.2.4 Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is required between the input pin and ground to prevent large
voltage transients from appearing at the input. This capacitor must be placed close to the IC using short leads. In
addition, the RMS current rating of the input capacitor must be selected to be at least ½ the DC load current. The
capacitor manufacturer data sheet must be checked to assure that this current rating is not exceeded. The
curves shown in Figure 16 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.
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Figure 16. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)
For an aluminum electrolytic capacitor, the voltage rating must be at least 1.25 times the maximum input voltage.
Caution must be exercised if solid tantalum capacitors are used. The tantalum capacitor voltage rating must be
twice the maximum input voltage. Table 4 and Table 5 show the recommended application voltage for AVX TPS
and Sprague 594D tantalum capacitors. TI recommends that they be surge 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.
Table 4. AVX TPS (1)
RECOMMENDED APPLICATION
VOLTAGE
VOLTAGE RATING
85°C RATING
(1)
3.3
6.3
5
10
10
20
12
25
15
35
Recommended Application Voltage for AVX TPS and Sprague 594D
Tantalum Chip Capacitors Derated for 85°C
Table 5. Sprague 594D (1)
RECOMMENDED APPLICATION
VOLTAGE
VOLTAGE RATING
85°C RATING
(1)
16
2.5
4
3.3
6.3
5
10
8
16
12
20
18
25
24
35
29
50
Recommended Application Voltage for AVX TPS and Sprague 594D
Tantalum Chip Capacitors Derated for 85°C
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Use caution when using only ceramic capacitors for input bypassing, because it may cause severe ringing at the
VIN pin. The important parameters for the input capacitor are the input voltage rating and the RMS current rating.
With a maximum input voltage of 12 V, an aluminum electrolytic capacitor with a voltage rating greater than 15 V
(1.25 × VIN) is required. The next higher capacitor voltage rating is 16 V.
The RMS current rating requirement for the input capacitor in a buck regulator is approximately ½ the DC load
current. In this example, with a 500-mA load, a capacitor with an RMS current rating of at least 250 mA is
required. The curves shown in Figure 16 can be used to select an appropriate input capacitor. From the curves,
locate the 16-V line and note which capacitor values have RMS current ratings greater than 250 mA.
For a through-hole design, a 100-μF, 16-V electrolytic capacitor (Panasonic HFQ series, Nichicon PL, Sanyo MVGX series or equivalent) would be adequate. Other types or other manufacturers' 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 Nichicon WF or UR and the NIC Components
NACZ series could be 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 4, and the Sprague 594D
series datasheet, a Sprague 594D 15-μF, 25-V capacitor is adequate.
9.2.1.2.5 Boost Capacitor (CB)
This capacitor develops the necessary voltage to turn the switch gate on fully. All applications must use a
0.01-μF, 50-V ceramic capacitor. For this application, and all applications, use a 0.01-μF, 50-V ceramic capacitor.
9.2.1.3 Application Curves
Continuous mode switching waveforms VIN = 20 V, VOUT = 5 V,
ILOAD = 500 mA L = 100 μH, COUT = 100 μF, COUTESR = 0.1 Ω
A: VSW pin voltage = 10 V/div
B: Inductor current = 0.2 A/div
C: Output ripple voltage = 50 mV/div ac-coupled
Load transient response for continuous mode VIN = 20 V, VOUT =
5 V, L = 100 μH, COUT = 100 μF, COUTESR = 0.1 Ω
A: Output voltage = 100 mV/div, ac-coupled
B: Load current = 100-mA to 500-mA load pulse
Figure 17. Horizontal Time Base: 1 μs/div
Figure 18. Horizontal Time Base: 50 μs/div
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9.2.2 Adjustable Output Voltage Typical Application
CIN = 22-μF, 50-V Tantalum, Sprague 199D Series
COUT = 47-μF, 25-V Tantalum, Sprague 595D Series
D1 = 3.3-A, 50-V Schottky Rectifier, IR 30WQ05F
L1 = 68-μH Sumida #RCR110D-680L
R1 = 1.5 kΩ, 1%
CB = 0.01-μF, 50-V Ceramic
For a 5-V output, select R2 to be 4.75 kΩ, 1%
where VREF = 1.21 V
Use a 1% resistor for best stability.
Figure 19. Adjustable Output Voltage Version
9.2.2.1 Design Requirements
Table 6 lists the design parameters of this example.
Table 6. Design Parameters
PARAMETER
VALUE
Regulated output voltage, VOUT
20
Maximum input voltage, VIN(max)
28
Maximum load current, ILOAD(max)
500
Switching frequency, F
Fixed at a nominal 260 kHz
9.2.2.2 Detailed Design Procedure
9.2.2.2.1 Programming Output Voltage
Select R1 and R2, as shown in Figure 19.
Use the following formula to select the appropriate resistor values.
where
•
VREF = 1.21 V
(1)
Select a value for R1 between 240 Ω and 1.5 kΩ. The lower resistor values minimize noise pickup in the sensitive
feedback pin. (For the lowest temperature coefficient and the best stability with time, use 1% metal film resistors.)
18
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(2)
Select R1 to be 1 kΩ, 1%. Solve for R2.
where
•
R2 = 1k (16.53 − 1) = 15.53 kΩ, closest 1% value is 15.4 kΩ
R2 = 15.4 kΩ
(3)
9.2.2.2.2 Inductor Selection (L1)
1. Calculate the inductor Volt • microsecond constant E • T (V • μs) from Equation 4.
where
•
•
VSAT = internal switch saturation voltage = 0.25 V
VD = diode forward voltage drop = 0.5 V
(4)
Calculate the inductor Volt • microsecond constant (E • T) with Equation 5.
(5)
2. 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.
E • T = 21.6 (V • μs)
3. On the horizontal axis, select the maximum load current.
ILOAD(max) = 500 mA
4. 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).
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.
5. Select an appropriate inductor from the four manufacturer's part numbers listed in Table 7. For information
on the different types of inductors, see the inductor selection in the fixed output voltage design procedure.
From Table 7, locate line L20, and select an inductor part number from the list of manufacturers' part
numbers.
Table 7. Inductor Manufacturers' Part Numbers
IND.
REF.
DESG.
INDUCTANCE
(μH)
CURRENT
(A)
L2
150
L3
100
L4
SCHOTT
RENCO
PULSE ENGINEERING
COILCRAFT
THROUGH
HOLE
SURFACE
MOUNT
THROUGH
HOLE
SURFACE
MOUNT
THROUGH
HOLE
SURFACE
MOUNT
SURFACE
MOUNT
0.21
67143920
67144290
RL-5470-4
RL1500-150
PE-53802
PE-53802-S
DO1608-154
0.26
67143930
67144300
RL-5470-5
RL1500-100
PE-53803
PE-53803-S
DO1608-104
68
0.32
67143940
67144310
RL-1284-68-43
RL1500-68
PE-53804
PE-53804-S
DO1608-683
L5
47
0.37
67148310
67148420
RL-1284-47-43
RL1500-47
PE-53805
PE-53805-S
DO1608-473
L6
33
0.44
67148320
67148430
RL-1284-33-43
RL1500-33
PE-53806
PE-53806-S
DO1608-333
L7
22
0.52
67148330
67148440
RL-1284-22-43
RL1500-22
PE-53807
PE-53807-S
DO1608-223
L9
220
0.32
67143960
67144330
RL-5470-3
RL1500-220
PE-53809
PE-53809-S
DO3308-224
L10
150
0.39
67143970
67144340
RL-5470-4
RL1500-150
PE-53810
PE-53810-S
DO3308-154
L11
100
0.48
67143980
67144350
RL-5470-5
RL1500-100
PE-53811
PE-53811-S
DO3308-104
L12
68
0.58
67143990
67144360
RL-5470-6
RL1500-68
PE-53812
PE-53812-S
DO3308-683
L13
47
0.7
67144000
67144380
RL-5470-7
RL1500-47
PE-53813
PE-53813-S
DO3308-473
L14
33
0.83
67148340
67148450
RL-1284-33-43
RL1500-33
PE-53814
PE-53814-S
DO3308-333
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Table 7. Inductor Manufacturers' Part Numbers (continued)
IND.
REF.
DESG.
INDUCTANCE
(μH)
CURRENT
(A)
L15
22
L18
220
L19
SCHOTT
RENCO
THROUGH
HOLE
SURFACE
MOUNT
THROUGH
HOLE
0.99
67148350
67148460
0.55
67144040
67144420
150
0.66
67144050
L20
100
0.82
L21
68
0.99
PULSE ENGINEERING
COILCRAFT
SURFACE
MOUNT
THROUGH
HOLE
SURFACE
MOUNT
SURFACE
MOUNT
RL-1284-22-43
RL1500-22
PE-53815
PE-53815-S
DO3308-223
RL-5471-2
RL1500-220
PE-53818
PE-53818-S
DO3316-224
67144430
RL-5471-3
RL1500-150
PE-53819
PE-53819-S
DO3316-154
67144060
67144440
RL-5471-4
RL1500-100
PE-53820
PE-53820-S
DO3316-104
67144070
67144450
RL-5471-5
RL1500-68
PE-53821
PE-53821-S
DO3316-683
9.2.2.2.3 Output Capacitor Selection (COUT)
1. Select an output capacitor from the capacitor code selection guide in Table 8. Using the inductance value
found in the inductor selection guide, step 1, locate the appropriate capacitor code corresponding to the
desired output voltage. Use the appropriate row of the capacitor code selection guide, in Table 8. For this
example, use the 15-V to 20-V row. The capacitor code corresponding to an inductance of 100 μH is C20.
2. Select an appropriate capacitor value and voltage rating, using the capacitor code, from the output capacitor
selection in Table 9. There are two solid tantalum (surface-mount) capacitor manufacturers and four
electrolytic (through-hole) capacitor manufacturers to choose from. TI recommends that both the
manufacturers and the manufacturer's series that are listed in the table be used. From the output capacitor
selection in Table 9, 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 following:
– Surface mount
– 33-μF, 25-V Sprague 594D series
– 33-μF, 25-V AVX TPS series
– Through hole
– 33-μF, 25-V Sanyo OS-CON SC series
– 120-μF, 35-V Sanyo MV-GX series
– 120-μF, 35-V Nichicon PL series
– 20-μF, 35-V 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.
Table 8. Capacitor Code Selection Guide
(1)
20
INDUCTANCE (μH)
CASE
STYLE (1)
OUTPUT
VOLTAGE (V)
22
33
47
68
100
150
220
SM and TH
1.21–2.5
—
—
—
—
C1
C2
C3
SM and TH
2.5–3.75
—
—
—
C1
C2
C3
C3
SM and TH
3.75–5
—
—
C4
C5
C6
C6
C6
SM and TH
5–6.25
—
C4
C7
C6
C6
C6
C6
SM and TH
6.25–7.5
C8
C4
C7
C6
C6
C6
C6
SM and TH
7.5–10
C9
C10
C11
C12
C13
C13
C13
SM and TH
10–12.5
C14
C11
C12
C12
C13
C13
C13
SM and TH
12.5–15
C15
C16
C17
C17
C17
C17
C17
SM and TH
15–20
C18
C19
C20
C20
C20
C20
C20
SM and TH
20–30
C21
C22
C22
C22
C22
C22
C22
TH
30–37
C23
C24
C24
C25
C25
C25
C25
SM = Surface mount and TH = Through hole
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Table 9. Output Capacitor Selection Table
OUTPUT CAPACITOR
SURFACE MOUNT
THROUGH HOLE
CAP.
REF.
DESG.
#
SPRAGUE
594D SERIES
(μF/V)
AVX TPS
SERIES
(μF/V)
SANYO OS-CON
SA SERIES
(μF/V)
SANYO MV-GX
SERIES
(μF/V)
NICHICON
PL SERIES
(μF/V)
PANASONIC
HFQ SERIES
(μF/V)
C1
120/6.3
100/10
100/10
220/35
220/35
220/35
C2
120/6.3
100/10
100/10
150/35
150/35
150/35
C3
120/6.3
100/10
100/35
120/35
120/35
120/35
C4
68/10
100/10
68/10
220/35
220/35
220/35
C5
100/16
100/10
100/10
150/35
150/35
150/35
C6
100/16
100/10
100/10
120/35
120/35
120/35
C7
68/10
100/10
68/10
150/35
150/35
150/35
C8
100/16
100/10
100/10
330/35
330/35
330/35
(1)
(2)
C9
100/16
100/16
100/16
330/35
330/35
330/35
C10
100/16
100/16
68/16
220/35
220/35
220/35
C11
100/16
100/16
68/16
150/35
150/35
150/35
C12
100/16
100/16
68/16
120/35
120/35
120/35
C13
100/16
100/16
100/16
120/35
120/35
120/35
C14
100/16
100/16
100/16
220/35
220/35
220/35
C15
47/20
68/20
47/20
220/35
220/35
220/35
C16
47/20
68/20
47/20
150/35
150/35
150/35
C17
47/20
68/20
47/20
120/35
120/35
120/35
C18
68/25
(2×) 33/25
47/ (1)
220/35
220/35
220/35
(1)
C19
33/25
33/25
33/25
150/35
150/35
150/35
C20
33/25
33/25
33/25 (1)
120/35
120/35
120/35
C21
33/35
(2×) 22/25
See (2)
150/35
150/35
150/35
(2)
C22
33/35
22/35
See
120/35
120/35
120/35
C23
See (2)
See (2)
See (2)
220/50
100/50
120/50
C24
See (2)
See (2)
See (2)
150/50
100/50
120/50
C25
(2)
(2)
(2)
150/50
82/50
82/50
See
See
See
The SC series of Os-Con capacitors (others are SA series)
The voltage ratings of the surface mount tantalum chip and Os-Con capacitors are too low to work at these voltages.
9.2.2.2.4 Catch Diode Selection (D1)
1. In normal operation, the average current of the catch diode is 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 must have a current rating greater than
the maximum current limit of the LM2674. The most stressful condition for this diode is a shorted output
condition. Schottky diodes provide the best performance, and in this example a 500-mA, 40-V Schottky diode
would be a good choice. If the circuit must withstand a continuous shorted output, a higher current (at least
1.2 A) Schottky diode is recommended.
2. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage.
3. Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best
performance and efficiency. The Schottky diode must be placed close to the LM2674 using short leads and
short printed-circuit traces.
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9.2.2.2.5 Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is required between the input pin and ground to prevent large
voltage transients from appearing at the input. This capacitor must be placed close to the IC using short leads. In
addition, the RMS current rating of the input capacitor must be selected to be at least ½ the DC load current. The
capacitor manufacturer data sheet must be checked to assure that this current rating is not exceeded. The
curves shown in Figure 16 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.
Figure 20. RMS Current Ratings for Low ESR Electrolytic Capacitors (Typical)
For an aluminum electrolytic capacitor, the voltage rating must be at least 1.25 times the maximum input voltage.
Caution must be exercised if solid tantalum capacitors are used. The tantalum capacitor voltage rating must be
twice the maximum input voltage. Table 10 and Table 5 show the recommended application voltage for AVX TPS
and Sprague 594D tantalum capacitors. TI also recommends that they be surge 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.
Table 10. AVX TPS (1)
RECOMMENDED APPLICATION
VOLTAGE
VOLTAGE RATING
85°C RATING
(1)
3.3
6.3
5
10
10
20
12
25
15
35
Recommended Application Voltage for AVX TPS and Sprague 594D
Tantalum Chip Capacitors Derated for 85°C
Table 11. Sprague 594D (1)
RECOMMENDED APPLICATION
VOLTAGE
VOLTAGE RATING
85°C RATING
(1)
22
2.5
4
3.3
6.3
5
10
8
16
12
20
Recommended Application Voltage for AVX TPS and Sprague 594D
Tantalum Chip Capacitors Derated for 85°C
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Table 11. Sprague 594D() (continued)
RECOMMENDED APPLICATION
VOLTAGE
VOLTAGE RATING
85°C RATING
18
25
24
35
29
50
Use caution when using only ceramic capacitors for input bypassing, because it may cause severe ringing at the
VIN pin. The important parameters for the input capacitor are the input voltage rating and the RMS current rating.
With a maximum input voltage of 28 V, an aluminum electrolytic capacitor with a voltage rating of at least 35 V
(1.25 × VIN) is required.
The RMS current rating requirement for the input capacitor in a buck regulator is approximately ½ the DC load
current. In this example, with a 500-mA load, a capacitor with an RMS current rating of at least 250 mA is
required. The curves shown in Figure 16 can be used to select an appropriate input capacitor. From the curves,
locate the 35-V line and note which capacitor values have RMS current ratings greater than 250 mA.
For a through-hole design, a 68-μF, 35-V electrolytic capacitor (Panasonic HFQ series, Nichicon PL, Sanyo MVGX series or equivalent) would be adequate. Other types or other manufacturers' 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 Nichicon WF or UR and the NIC Components
NACZ series could be 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 note 1 of Table 5, and the
Sprague 594D series datasheet, a Sprague 594D 15-μF, 50-V capacitor is adequate.
9.2.2.2.6 Boost Capacitor (CB)
This capacitor develops the necessary voltage to turn the switch gate on fully. All applications must use a
0.01-μF, 50-V ceramic capacitor. For this application, and all applications, use a 0.01-μF, 50-V ceramic capacitor.
9.2.2.3 Application Curves
Discontinuous mode switching waveforms
VIN = 20 V, VOUT = 5 V, 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
C: Output ripple voltage = 20 mV/div ac-coupled
Load transient response for discontinuous mode VIN = 20 V,
VOUT = 5 V, L = 47 μH, COUT = 68 μF, COUTESR = 50 mΩ
A: Output voltage = 100 mV/div, ac-coupled
B: Load current = 100-mA to 400-mA load pulse
Figure 21. Horizontal Time Base: 1 μs/div
Figure 22. Horizontal Time Base: 200 μs/div
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9.2.3 Typical Application for All Output Voltage Versions
Figure 23. Typical Application
9.2.3.1 Application Curves
for continuous mode operation
Figure 24. LM2674, 3.3-V Version
Figure 25. LM2674, 5-V Version
Figure 26. LM2674, 12-V Version
Figure 27. LM2674, Adjustable Version
10 Power Supply Recommendations
The LM2674 is designed to operate from an input voltage supply up to 40 V. This input supply must be well
regulated and able to withstand maximum input current and maintain a stable voltage.
24
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11 Layout
11.1 Layout Guidelines
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 15 and Figure 19) must be wide printed-circuit traces and
must be kept as short as possible. For best results, external components must be placed as close to the switcher
IC as possible using ground plane construction or single point grounding.
If open core inductors are used, take special care 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, take special care as to the location of the feedback resistors and the
associated wiring. Physically place both resistors near the IC, and route the wiring away from the inductor,
especially an open core type of inductor.
11.1.1 WSON Package Devices
The LM2674 is offered in the 16-pin WSON surface mount package to allow for increased power dissipation
compared to the 8-pin SOIC and PDIP.
The die attach pad (DAP) must be connected to PCB ground plane. For CAD and assembly guidelines refer to
AN-1187 Leadless Leadfram Package (LLP).
11.2 Layout Examples
CIN = 15-μF, 25-V, Solid Tantalum Sprague 594D series
COUT = 68-μF, 10-V, Solid Tantalum Sprague 594D series
D1 = 1-A, 40-V Schottky Rectifier, Surface Mount
L1 = 47-μH, L13, Coilcraft DO3308
CB = 0.01-μF, 50-V Ceramic
Figure 28. Typical Surface-Mount PCB Layout, Fixed Output (4x Size)
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Layout Examples (continued)
CIN = 15-μF, 50-V, Solid Tantalum Sprague 594D series
COUT = 33-μF, 25-V, Solid Tantalum Sprague 594D series
D1 = 1-A, 40-V Schottky Rectifier, Surface Mount
L1 = 100-μH, L20, Coilcraft DO3316
CB = 0.01-μF, 50-V Ceramic
R1 = 1k, 1%
R2 = Use formula in Detailed Design Procedure
Figure 29. Typical Surface-Mount PCB Layout, Adjustable Output (4x Size)
26
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
For related documentation see the following:
AN-1187 Leadless Leadfram Package (LLP)
12.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.4 Trademarks
E2E is a trademark of Texas Instruments.
SIMPLE SWITCHER, WEBENCH are registered trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
12.5 Electrostatic Discharge Caution
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.
12.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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27
PACKAGE OPTION ADDENDUM
www.ti.com
1-Aug-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
LM2674LD-ADJ/NOPB
ACTIVE
WSON
NHN
16
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 125
S000CB
Samples
LM2674LDX-5.0/NOPB
ACTIVE
WSON
NHN
16
4500
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 125
S000BB
Samples
LM2674M-12
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-40 to 125
2674
M-12
LM2674M-12/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2674
M-12
Samples
LM2674M-3.3/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2674
M3.3
Samples
LM2674M-5.0
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-40 to 125
2674
M5.0
LM2674M-5.0/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2674
M5.0
Samples
LM2674M-ADJ/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2674
MADJ
Samples
LM2674MX-12/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2674
M-12
Samples
LM2674MX-3.3/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2674
M3.3
Samples
LM2674MX-5.0/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2674
M5.0
Samples
LM2674MX-ADJ/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2674
MADJ
Samples
LM2674N-3.3/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 125
LM2674
N-3.3
Samples
LM2674N-5.0/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 125
LM2674
N-5.0
Samples
LM2674N-ADJ/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 125
LM2674
N-ADJ
Samples
(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.
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
1-Aug-2022
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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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