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LM2675
SNVS129F – MAY 2004 – REVISED JUNE 2016
LM2675 SIMPLE SWITCHER® Power Converter High Efficiency
1-A Step-Down Voltage Regulator
1 Features
3 Description
•
•
The LM2675 series of regulators are monolithic
integrated DC-DC converter circuits built with a
LMDMOS process. These regulators provide all the
active functions for a step-down (buck) switching
regulator, capable of driving a 1-A 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
Package
Requires only 5 External Components
3.3-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 1-A Output Load Current
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
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 LM2675 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.
2 Applications
•
•
•
Device Information(1)
Simple High Efficiency (>90%) Step-Down (Buck)
Regulator
Efficient Preregulator for Linear Regulators
Positive-to-Negative Converter
PART NUMBER
LM2675
PACKAGE
BODY SIZE (NOM)
SOIC (8)
5.00 mm × 6.20 mm
PDIP (8)
10.16 mm × 6.60 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
Copyright © 2016, Texas Instruments Incorporated
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.
LM2675
SNVS129F – MAY 2004 – 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
7.9
4
4
4
4
5
5
5
6
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics – 3.3 V ..............................
Electrical Characteristics – 5 V .................................
Electrical Characteristics – 12 V ...............................
Electrical Characteristics – Adjustable......................
Electrical Characteristics – All Output Voltage
Versions .....................................................................
7.10 Typical Characteristics ............................................
7.11 Typical Characteristics – Fixed Output Voltage
Versions .....................................................................
8
6
7
9
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 Application .................................................. 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
Detailed Description ............................................ 10
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision E (June 2005) to Revision F
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
•
Deleted all instances of the computer design software LM267X Made Simple (version 6.0) ................................................ 1
2
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5 Description (continued)
A family of standard inductors for use with the LM2675 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.
Other features include ±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
NHN Package
16-Pin WSON
Top View
CB
1
8
VSW
NC
2
7
VIN
NC
3
6
GND
FB
4
5
ON/OFF
Not to scale
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
Pin Functions
PIN
NAME
I/O
DESCRIPTION
D, P
NHN
CB
1
1
I
Boot-strap 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 adjustable version or connect this pin directly to the output capacitor
for a fixed output version.
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.
2, 3
2, 3, 4, 5,
6, 7, 10, 13
—
No connect pins.
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.
VIN
7
14
I
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.
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.
NC
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SNVS129F – MAY 2004 – REVISED JUNE 2016
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7 Specifications
7.1 Absolute Maximum Ratings
over recommended operating junction temperature range of –40°C to 125°C (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)
NHN package
See AN-1187
Maximum junction temperature, TJ
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, contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
7.2 ESD Ratings
V(ESD)
(1)
(2)
Electrostatic discharge
VALUE
UNIT
±2000
V
MAX
UNIT
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) (2)
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
over operating free-air temperature range (unless otherwise noted)
MIN
TJ
Supply voltage
6.5
40
V
Temperature
–40
125
°C
7.4 Thermal Information
LM2675
THERMAL METRIC (1) (2)
SOIC (D)
PDIP (P)
NHN (WSON)
8 PINS
8 PINS
16 PINS
UNIT
RθJA
Junction-to-ambient thermal resistance (3)
105
95
—
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
—
—
—
°C/W
RθJB
Junction-to-board thermal resistance
—
—
—
°C/W
ψJT
Junction-to-top characterization parameter
—
—
—
°C/W
ψJB
Junction-to-board characterization parameter
—
—
—
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
—
—
—
°C/W
(1)
(2)
(3)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
Thermal resistances were simulated on 4-layer JEDEC board.
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. See Application Information in the application note accompanying this data
sheet. 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, refer to AN-1187 Leadless
Leadframe Package (LLP).
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7.5 Electrical Characteristics – 3.3 V
TJ = 25°C (unless otherwise noted; see Figure 19) (1)
PARAMETER
VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A
VOUT
Output voltage
VIN = 6.5 V to 40 V,
ILOAD = 20 mA to 500 mA
Efficiency
η
(1)
(2)
(3)
MIN (2)
TYP (3)
TJ = 25°C
3.251
3.3
TJ = –40°C to 125°C
3.201
TJ = 25°C
3.251
TJ = –40°C to 125°C
3.201
TEST CONDITIONS
VIN = 12 V, ILOAD = 1 A
MAX (2)
3.35
3.399
3.3
UNIT
3.35
V
3.399
86%
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator performance. When the LM2675 is used as shown in Figure 19 test circuits, system performance is as specified by
the system parameters section of Electrical Characteristics.
All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits
at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used
to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
7.6 Electrical Characteristics – 5 V
TJ = 25°C (unless otherwise noted; see Figure 19) (1)
PARAMETER
TEST CONDITIONS
VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A
VOUT
Output voltage
Efficiency
(1)
(2)
(3)
TJ = –40°C to 125°C
TJ = 25°C
VIN = 6.5 V to 40 V,
ILOAD = 20 mA to 500 mA
η
TJ = 25°C
TJ = –40°C to 125°C
MIN (2)
TYP (3)
4.925
5
5.075
5
5.075
4.85
4.925
5.15
4.85
VIN = 12 V, ILOAD = 1 A
MAX (2) UNIT
V
5.15
90%
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator performance. When the LM2675 is used as shown in Figure 19 test circuits, system performance is as specified by
the system parameters section of Electrical Characteristics.
All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits
at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used
to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
7.7 Electrical Characteristics – 12 V
TJ = 25°C (unless otherwise noted; see Figure 19) (1)
PARAMETER
VOUT
Output voltage
VIN = 15 V to 40 V, ILOAD = 20 mA to 1 A
η
Efficiency
VIN = 24 V, ILOAD = 1 A
(1)
(2)
(3)
MIN (2)
TYP (3)
TJ = 25°C
11.82
12
TJ = –40°C to 125°C
11.64
TEST CONDITIONS
MAX (2) UNIT
12.18
12.36
V
94%
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator performance. When the LM2675 is used as shown in Figure 19 test circuits, system performance is as specified by
the system parameters section of Electrical Characteristics.
All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits
at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used
to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
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7.8 Electrical Characteristics – Adjustable
TJ = 25°C (unless otherwise noted; see Figure 19) (1)
PARAMETER
Feedback
voltage
VFB
Efficiency
η
(1)
(2)
(3)
TEST CONDITIONS
MIN (2)
TYP (3)
1.21
VIN = 8 V to 40 V, ILOAD = 20 mA to 1 A,
VOUT programmed for 5 V (see Figure 19)
TJ = 25°C
1.192
TJ = –40°C to 125°C
1.174
VIN = 6.5 V to 40 V, ILOAD = 20 mA to 500
mA, VOUT programmed for 5 V (see
Figure 19)
TJ = 25°C
1.192
TJ = –40°C to 125°C
1.174
MAX (2) UNIT
1.228
1.246
1.21
V
1.228
1.246
VIN = 12 V, ILOAD = 1 A
90%
External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect
switching regulator performance. When the LM2675 is used as shown in Figure 19 test circuits, system performance is as specified by
the system parameters section of Electrical Characteristics.
All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits
at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used
to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
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)
PARAMETER
IQ
Quiescent current
VFEEDBACK = 8 V for 3.3 V, 5 V, and adjustable versions
2.5
VFEEDBACK = 15 V for 12 V versions
2.5
ISTBY
Standby quiescent current
ICL
Current limit
IL
Output leakage current
RDS(ON)
Switch on-resistance
ISWITCH = 1 A
fO
Oscillator frequency
Measured at switch pin
D
Minimum duty cycle
IBIAS
Feedback bias current
VS/D
ON/OFF pin voltage
IS/D
ON/OFF pin current
(1)
(2)
6
MIN (1) TYP (2)
TEST CONDITIONS
ON/OFF Pin = 0 V
TJ = 25°C
50
TJ = –40°C to 125°C
TJ = 25°C
3.6
1.55
1.2
mA
mA
100
150
1.25
TJ = –40°C to 125°C
MAX (1) UNIT
2.1
2.2
μA
A
VSWITCH = 0 V, ON/OFF Pin = 0 V, VIN = 40 V
1
25
μA
VSWITCH = −1 V, ON/OFF Pin = 0 V
6
15
mA
0.25
0.3
TJ = 25°C
TJ = –40°C to 125°C
0.5
TJ = 25°C
TJ = –40°C to 125°C
260
225
TJ = 25°C
275
Ω
kHz
95%
TJ = –40°C to 125°C
0%
VFEEDBACK = 1.3 V, adjustable version only
85
TJ = 25°C
nA
1.4
TJ = –40°C to 125°C
ON/OFF Pin = 0 V
0.8
TJ = 25°C
TJ = –40°C to 125°C
2
20
7
37
V
μA
All limits specified at room temperature and at temperature extremes. All room temperature limits are 100% production tested. All limits
at temperature extremes are specified through correlation using standard Statistical Quality Control (SQC) methods. All limits are used
to calculate Average Outgoing Quality Level (AOQL).
Typical numbers are at 25°C and represent the most likely norm.
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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 Option
Figure 14. Dropout Voltage, 5-V Option
7.11 Typical Characteristics – Fixed Output Voltage Versions
see Figure 19
VSW pin voltage, 10 V/div
Inductor current, 0.5 A/div
Output ripple voltage,
20 mV/div AC-coupled
VIN = 20 V, VOUT = 5 V,
ILOAD = 1 A, L = 47 μH,
COUT = 68 μF,
COUTESR = 50 mΩ
Figure 15. Continuous Mode Switching Waveforms,
Horizontal Time Base: 1 μs/div
Output voltage, 100 mV/div,
AC-coupled
Load current: 200-mA
to 1-A load pulse
VIN = 20 V, VOUT = 5 V,
ILOAD = 1 A, L = 47 μH,
COUT = 68 μF,
COUTESR = 50 mΩ
Figure 17. Load Transient Response for Continuous Mode,
Horizontal Time Base: 50 μs/div
VSW pin voltage, 10 V/div
Inductor current, 0.5 A/div
Output ripple voltage,
20 mV/div AC-coupled
VIN = 20 V, VOUT = 5 V,
ILOAD = 300 mA, L = 15 μH,
COUT = 68 μF (2×),
COUTESR = 25 mΩ
Figure 16. Discontinuous Mode Switching Waveforms,
Horizontal Time Base: 1 μs/div
Output voltage, 100 mV/div,
AC-coupled
Load current: 100-mA
to 400-mA load pulse
VIN = 20 V, VOUT = 5 V,
L = 47 μH,
COUT = 68 μF (2×),
COUTESR = 50 mΩ
Figure 18. Load Transient Response for Discontinuous
Mode, Horizontal Time Base: 200 μs/div
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8 Detailed Description
8.1 Overview
The LM2675 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 1 A,
and highly efficient operation. The LM2675 is part of the SIMPLE SWITCHER® family of power converters. A
complete design uses a minimum number of external components, which have been predetermined 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. See LM2670 SIMPLE SWITCHER® High Efficiency 3A Step-Down
Voltage Regulator with Sync for additional application information.
8.2 Functional Block Diagram
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8.3 Feature Description
8.3.1 Adjustable Output Voltage
The voltage regulation loop in the LM2675 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 needed to program the ratio from output
voltage VOUT to VFB. The resistor is connected from the VOUT of the LM2674 to ground with the mid-point
connecting to the FB pin. The voltage reference system produces a precise voltage reference over temperature.
The internal REF voltage is typically 1.21 V. To program the output voltage of the LM2675 to be a certain value
VOUT, R1 can be calculated with a selected R2. See Programming Output Voltage for adjustable output voltage
typical application. The recommended range for R2 in most application is from 10 kΩ to 100 kΩ. If the resistor
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 regulate it. The load connected to the output could be damaged under such a
condition. Do not short FB pin to ground when the LM2675 is enabled. It is important to route the feedback trace
away from the noisy area of the PCB. For more layout recommendations, see Layout.
10
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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 20 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 LM2675 is a step-down DC-DC regulator. The device is typically used to convert a higher DC voltage to a
lower DC voltage with a maximum output current of 1 A. The following design procedure can be used to select
components for the LM2675.
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 should exercise caution in selection of the output filter
components. When an application designed to these specific operating conditions is subjected to a current limit
fault condition, it may be possible to observe a large hysteresis in the current limit. This can affect the output
voltage of the device until the load current is reduced sufficiently to allow the current limit protection circuit to
reset itself.
Under current limiting conditions, the LM2675 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. It should be noted that 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 LM2675 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 Application
9.2.1 Fixed Output Voltage Application
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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 19. Fixed Output Voltage Schematic
9.2.1.1 Design Requirements
Table 1 lists the design requirements for the fixed output voltage application.
Table 1. Design Parameters
PARAMETER
VALUE
Regulated output voltage, VOUT
5V
Maximum input voltage, VIN(max)
12 V
Maximum load current, ILOAD(max)
1A
9.2.1.2 Detailed Design Procedure
9.2.1.2.1 Inductor Selection (L1)
Select the correct inductor value selection guide from Figure 21, Figure 22, or Figure 23 (output voltages of
3.3 V, 5 V, or 12 V respectively). For all other voltages, see Detailed Design Procedure. Use the inductor
selection guide for the 5-V version shown in Figure 22.
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 22, the inductance region intersected by the 12-V
horizontal line and the 1-A vertical line is 33 μH, and the inductor code is L23.
Select an appropriate inductor from the four manufacturer's part numbers listed in Table 2. Each manufacturer
makes a different style of inductor to allow flexibility in meeting various design requirements. The inductance
value required is 33 μH. From the table in Table 2, go to the L23 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.
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Table 2. Inductor Manufacturers' Part Numbers
IND.
REF.
DESG.
INDUCTANCE
(μH)
CURRENT
(A)
L4
68
L5
47
L6
SCHOTT
RENCO
PULSE ENGINEERING
COILCRAFT
THROUGH
HOLE
SURFACE
MOUNT
THROUGH
HOLE
SURFACE
MOUNT
THROUGH
HOLE
SURFACE
MOUNT
SURFACE
MOUNT
0.32
67143940
67144310
RL-1284-68-43
RL1500-68
PE-53804
PE-53804-S
DO1608-683
0.37
67148310
67148420
RL-1284-47-43
RL1500-47
PE-53805
PE-53805-S
DO1608-473
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
L15
22
0.99
67148350
67148460
RL-1284-22-43
RL1500-22
PE-53815
PE-53815-S
DO3308-223
L18
220
0.55
67144040
67144420
RL-5471-2
RL1500-220
PE-53818
PE-53818-S
DO3316-224
L19
150
0.66
67144050
67144430
RL-5471-3
RL1500-150
PE-53819
PE-53819-S
DO3316-154
L20
100
0.82
67144060
67144440
RL-5471-4
RL1500-100
PE-53820
PE-53820-S
DO3316-104
L21
68
0.99
67144070
67144450
RL-5471-5
RL1500-68
PE-53821
PE-53821-S
DO3316-683
L22
47
1.17
67144080
67144460
RL-5471-6
—
PE-53822
PE-53822-S
DO3316-473
L23
33
1.4
67144090
67144470
RL-5471-7
—
PE-53823
PE-53823-S
DO3316-333
L24
22
1.7
67148370
67148480
RL-1283-22-43
—
PE-53824
PE-53824-S
DO3316-223
L27
220
1
67144110
67144490
RL-5471-2
—
PE-53827
PE-53827-S
DO5022P-224
L28
150
1.2
67144120
67144500
RL-5471-3
—
PE-53828
PE-53828-S
DO5022P-154
L29
100
1.47
67144130
67144510
RL-5471-4
—
PE-53829
PE-53829-S
DO5022P-104
L30
68
1.78
67144140
67144520
RL-5471-5
—
PE-53830
PE-53830-S
DO5022P-683
9.2.1.2.2 Output Capacitor Selection (COUT)
Select an output capacitor from Table 3. Using the output voltage and the inductance value found in the inductor
selection guide, step 1, locate the appropriate capacitor value and voltage rating. 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 using both the manufacturers and the
manufacturer's series that are listed in the table.
Use the 5-V section in Table 3. Choose a capacitor value and voltage rating from the line that contains the
inductance value of 33 μH. The capacitance and voltage rating values corresponding to the 33-μH inductor are
the surface mount and through hole.
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
• 220-μF, 35-V Sanyo MV-GX series
• 220-μF, 35-V Nichicon PL series
• 220-μF, 35-V Panasonic HFQ series
14
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Table 3. Output Capacitor Table
OUTPUT CAPACITOR
OUTPUT
VOLTAGE
(V)
3.3
5
12
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
9.2.1.2.3 Catch Diode Selection (D1)
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 LM2675. The most stressful condition
for this diode is a shorted output condition (see Table 4). In this example, a 1-A, 20-V Schottky diode provides
the best performance. If the circuit must withstand a continuous shorted output, TI recommends a Schottky diode
of higher current.
The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage. 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 LM2675 using short leads and short printed circuit traces.
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Table 4. Schottky Diode Selection Table
VR
20 V
30 V
40 V
50 V
1-A DIODES
3-A DIODES
SURFACE MOUNT
THROUGH HOLE
SURFACE MOUNT
THROUGH HOLE
SK12
1N5817
SK32
1N5820
B120
SR102
—
SR302
SK13
1N5818
SK33
1N5821
B130
11DQ03
30WQ03F
31DQ03
MBRS130
SR103
—
—
SK14
1N5819
SK34
1N5822
B140
11DQ04
30BQ040
MBR340
MBRS140
SR104
30WQ04F
31DQ04
10BQ040
—
MBRS340
SR304
10MQ040
—
MBRD340
—
15MQ040
—
—
—
SK15
MBR150
SK35
MBR350
B150
11DQ05
30WQ05F
31DQ05
10BQ050
SR105
—
SR305
9.2.1.2.4 Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground to prevent large
voltage transients from appearing at the input. This capacitor must be located 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.
Figure 20 shows 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)
16
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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 3 shows 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.
Use caution when using 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) would be needed. 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 1-A load, a capacitor with a RMS current rating of at least 500 mA is needed. The
curves shown in Figure 20 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 500 mA.
For a through hole design, a 330-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 5, and the Sprague 594D
series data sheet, a Sprague 594D 15-μF, 25-V capacitor is adequate.
Table 5. Sprague 594D
RECOMMENDED APPLICATION VOLTAGE
VOLTAGE RATING
85°C RATING
2.5
4
3.3
6.3
5
10
8
16
12
20
18
25
24
35
29
50
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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.
9.2.1.3 Application Curves
Figure 22. LM2675, 5-V Output
Figure 21. LM2675, 3.3-V Output
Figure 23. LM2675, 12-V Output
18
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9.2.2 Adjustable Output Voltage Application
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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
Figure 24. Adjustable Output Voltage Schematic
9.2.2.1 Design Requirements
Table 1 lists the design requirements for the adjustable output voltage application.
Table 6. Design Parameters
PARAMETER
VALUE
Regulated output voltage, VOUT
20 V
Maximum input voltage, VIN(max)
28 V
Maximum load current, ILOAD(max)
1A
Switching frequency, F
Fixed at a nominal 260 kHz
9.2.2.2 Detailed Design Procedure
9.2.2.2.1 Programming Output Voltage
Selecting R1 and R2, as shown in Figure 19.
Use Equation 1 to select the appropriate resistor values.
§ R2 ·
VREF ¨ 1
¸
R1 ¹
©
VOUT
where
•
VREF = 1.21 V
(1)
Select R1 to be 1 kΩ, 1%. Solve for R2 using Equation 2.
R2
§V
R1 ¨ OUT
© VREF
·
1¸
¹
§ 20 V
1k: ¨
© 1.23 V
·
1¸
¹
(2)
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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
with Equation 3.
§V
·
R 2 R1 ¨ OUT 1¸
© VREF
¹
(3)
R2 = 1k (16.53 − 1) = 15.53 kΩ, closest 1% value is 15.4 kΩ.
R2 = 15.4 kΩ.
9.2.2.2.2 Inductor Selection (L1)
Calculate the inductor Volt × microsecond constant E × T (V × μs) from Equation 4.
VOUT VD
1000
u
E u T (VIN(MAX) VOUT VSAT ) u
(V u Ps)
VIN(MAX) VSAT VD 260
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.
20 0.5
1000
E u T (28 20 0.25) u
u
(V u Ps)
28 0.25 0.5 260
20.5
E u T (7.75) u
u 3.85(V u Ps)
28.25
(5)
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 in Figure 25. E × T = 21.6 (V × μs).
On the horizontal axis, select the maximum load current (ILOAD(max) = 1 A).
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 25, the inductance region intersected by the 21.6 (V × μs) horizontal line and the 1-A vertical line is
68 μH, and the inductor code is L30.
Select an appropriate inductor from the four manufacturer's part numbers listed in Table 2. For information on the
different types of inductors, see the inductor selection in the fixed output voltage design procedure. From
Table 2, locate line L30, and select an inductor part number from the list of manufacturers' part numbers.
9.2.2.2.3 Output Capacitor SeIection (COUT)
Select an output capacitor from the capacitor code selection guide in Table 7. 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 7. For this example, use the
15 V to 20 V row. The capacitor code corresponding to an inductance of 68 μH is C20.
20
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Table 7. Capacitor Code Selection Guide
(1)
INDUCTANCE (μH)
CASE
STYLE (1)
OUTPUT
VOLTAGE (V)
22
33
47
SM and TH
1.21 to 2.5
—
—
SM and TH
2.5 to 3.75
—
—
SM and TH
3.75 to 5
—
SM and TH
5 to 6.25
—
SM and TH
6.25 to 7.5
C8
C4
C7
C6
C6
C6
C6
SM and TH
7.5 to 10
C9
C10
C11
C12
C13
C13
C13
SM and TH
10 to 12.5
C14
C11
C12
C12
C13
C13
C13
SM and TH
12.5 to 15
C15
C16
C17
C17
C17
C17
C17
SM and TH
15 to 20
C18
C19
C20
C20
C20
C20
C20
SM and TH
20 to 30
C21
C22
C22
C22
C22
C22
C22
TH
30 to 37
C23
C24
C24
C25
C25
C25
C25
68
100
150
220
—
—
C1
C2
C3
—
C1
C2
C3
C3
—
C4
C5
C6
C6
C6
C4
C7
C6
C6
C6
C6
SM = surface mount, TH = through hole
Select an appropriate capacitor value and voltage rating, using the capacitor code, from the output capacitor
selection table in Table 8. There are two solid tantalum (surface mount) capacitor manufacturers and four
electrolytic (through hole) capacitor manufacturers to choose from. TI recommends using both the manufacturers
and the manufacturer's series that are listed in Table 8. From Table 8, choose a capacitor value (and voltage
rating) that intersects the capacitor code(s) selected in section A, C20. The capacitance and voltage rating
values corresponding to the capacitor code C20 are the surface mount and through hole.
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
• 120-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. See the capacitor manufacturers' data sheet for this information.
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Table 8. 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
47/25 (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)
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 LM2675. The most stressful condition for this diode is a shorted output condition (see Table 4). Schottky
diodes provide the best performance, and in this example a 1-A, 40-V Schottky diode would be a good choice. If
the circuit must withstand a continuous shorted output, TI recommends a Schottky diode of higher current (at
least 2.2 A).
The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage. 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 LM2675 using short leads and short printed circuit traces.
22
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9.2.2.2.5 Input Capacitor (CIN)
A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground to prevent large
voltage transients from appearing at the input. This capacitor must be located 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 20 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 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 9 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 9. AVX TPS
RECOMMENDED APPLICATION VOLTAGE
VOLTAGE RATING
85°C RATING
3.3
6.3
5
10
10
20
12
25
15
35
Use caution when using 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) would be needed.
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 1-A load, a capacitor with a RMS current rating of at least 500 mA is needed. The
curves shown in Figure 20 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 500 mA.
For a through hole design, a 330-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 Table 5, and the Sprague 594D
series data sheet, 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.
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9.2.2.3 Application Curve
Figure 25. LM2675, Adjustable Output
10 Power Supply Recommendations
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 LM2675. For ensured performance, the input
voltage must be in the range of 6.5 V to 40 V. The VIN pin must always be bypassed with an input capacitor
located close to this pin and GND.
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 19 and Figure 24) 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 locate 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 LM2675 is offered in the 16-pin WSON surface-mount package to allow for increased power dissipation
compared to the SOIC and PDIP.
The die attach pad (DAP) can and must be connected to PCB Ground plane or island. For CAD and assembly
guidelines see AN-1187 Leadless Leadframe Package (LLP).
11.2 Layout Examples
CIN = 15-μF, 50-V, Solid Tantalum Sprague 594D series
COUT = 68-μF, 16-V, Solid Tantalum Sprague 594D series
D1 = 1-A, 40-V Schottky Rectifier, surface mount
L1 = 33-μH, L23, Coilcraft DO3316
CB = 0.01-μF, 50-V ceramic
Figure 26. Typical Surface Mount PC Board Layout, Fixed Output
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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 = 68-μH, L30, Coilcraft DO3316
CB = 0.01-μF, 50-V ceramic
R1 = 1k, 1%
R2 = Use formula in Detailed Design Procedure
Figure 27. Typical Surface Mount PC Board Layout, Adjustable Output
26
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SNVS129F – MAY 2004 – REVISED JUNE 2016
12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Documentation
For related documentation see the following:
• AN-1187 Leadless Leadframe Package (LLP)
• LM2670 SIMPLE SWITCHER® High Efficiency 3A Step-Down Voltage Regulator with Sync
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 is a registered trademark 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)
LM2675LD-5.0/NOPB
ACTIVE
WSON
NHN
16
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 125
S000FB
Samples
LM2675LD-ADJ/NOPB
ACTIVE
WSON
NHN
16
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 125
S000GB
Samples
LM2675M-12
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-40 to 125
2675
M-12
LM2675M-12/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2675
M-12
Samples
LM2675M-3.3/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2675
M3.3
Samples
LM2675M-5.0
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-40 to 125
2675
M5.0
LM2675M-5.0/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2675
M5.0
LM2675M-ADJ
NRND
SOIC
D
8
95
Non-RoHS
& Green
Call TI
Level-1-235C-UNLIM
-40 to 125
2675
MADJ
LM2675M-ADJ/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2675
MADJ
Samples
LM2675MX-12/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2675
M-12
Samples
LM2675MX-3.3/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2675
M3.3
Samples
LM2675MX-5.0/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2675
M5.0
Samples
LM2675MX-ADJ/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
Call TI | SN
Level-1-260C-UNLIM
-40 to 125
2675
MADJ
Samples
LM2675N-12/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 125
LM2675
N-12
Samples
LM2675N-3.3/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 125
LM2675
N-3.3
Samples
LM2675N-5.0/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 125
LM2675
N-5.0
Samples
LM2675N-ADJ/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 125
LM2675
N-ADJ
Samples
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
1-Aug-2022
(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)
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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