TI LM2670SX

LM2670EP
LM2670EP Enhanced Plastic SIMPLE SWITCHER High Efficiency 3A Step-Down
Voltage Regulator with Sync
Literature Number: SNVS278A
March 22, 2011
LM2670EP
Enhanced Plastic SIMPLE SWITCHER® High Efficiency 3A
Step-Down Voltage Regulator with Sync
General Description
Features
The LM2670EP series of regulators are monolithic integrated
circuits which provide all of the active functions for a stepdown (buck) switching regulator capable of driving up to 3A
loads with excellent line and load regulation characteristics.
High efficiency (>90%) is obtained through the use of a low
ON-resistance DMOS power switch. The series consists of
fixed output voltages of 3.3V, 5V and 12V and an adjustable
output version.
The SIMPLE SWITCHER concept provides for a complete
design using a minimum number of external components. The
switching clock frequency can be provided by an internal fixed
frequency oscillator (260KHz) or from an externally provided
clock in the range of 280KHz to 400Khz which allows the use
of physically smaller sized components. A family of standard
inductors for use with the LM2670EP are available from several manufacturers to greatly simplify the design process. The
external Sync clock provides direct and precise control of the
output ripple frequency for consistent filtering or frequency
spectrum positioning.
The LM2670EP series also has built in thermal shutdown,
current limiting and an ON/OFF control input that can power
down the regulator to a low 50μA quiescent current standby
condition. The output voltage is guaranteed to a ±2% tolerance.
ENHANCED PLASTIC
• Extended Temperature Performance of −40°C to 125°C
• Baseline Control - Single Fab & Assembly Site
• Process Change Notification (PCN)
• Qualification & Reliability Data
• Solder (PbSn) Lead Finish is standard
• Enhanced Diminishing Manufacturing Sources (DMS)
Support
■ Efficiency up to 94%
■ Simple and easy to design with (using off-the-shelf
external components)
■ 150 mΩ DMOS output switch
■ 3.3V, 5V and 12V fixed output and adjustable (1.2V to
37V ) versions
■ 50μA standby current when switched OFF
■ ±2%maximum output tolerance over full line and load
conditions
■ Wide input voltage range: 8V to 40V
■ External Sync clock capability (280KHz to 400KHz)
■ 260 KHz fixed frequency internal oscillator
Applications
■ Simple to design, high efficiency (>90%) step-down
switching regulators
■ Efficient system pre-regulator for linear voltage regulators
■ Selected Military Applications
■ Selected Avionics Applications
Ordering Information
PART NUMBER
VID PART NUMBER
NS PACKAGE NUMBER (Note 3)
LM2670SX-ADJEP
V62/04628-01
TS7B
(Note 1, Note 2)
TBD
TBD
Note 1: For the following (Enhanced Plastic) versions, check for availability: LM2670SD-12EP, LM2670SD-3.3EP, LM2670SD-5.0EP, LM2670SDADJEP, LM2670SDX-12EP, LM2670SDX-3.3EP, LM2670SDX-5.0EP, LM2670SDX-ADJEP, LM2670T-12EP, LM2670T-3.3EP, LM2670T-5.0EP,
LM2670T-ADJEP, LM2670S-12EP, LM2670S-3.3EP, LM2670S-5.0EP, LM2670S-ADJEP, LM2670SX-12EP, LM2670SX-3.3EP, LM2670SX-5.0EP. Parts
listed with an "X" are provided in Tape & Reel and parts without an "X" are in Rails.
Note 2: FOR ADDITIONAL ORDERING AND PRODUCT INFORMATION, PLEASE VISIT THE ENHANCED PLASTIC WEB SITE AT: www.national.com/
mil
Note 3: Refer to package details under Physical Dimensions
SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation
© 2011 National Semiconductor Corporation
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LM2670EP Enhanced PlasticSIMPLE SWITCHER® High Efficiency 3A Step-Down Voltage
Regulator with Sync
OBSOLETE
LM2670EP Enhanced Plastic
Typical Application
20097703
Connection Diagrams
TO-263 Package
Top View
TO-220 Package
Top View
20097701
20097702
See NSC Package Number TS7B
See NSC Package Number TA07B
Top View
20097741
LLP-14
See NS package Number SRC14A
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If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Input Supply Voltage
ON/OFF Pin Voltage
Switch Voltage to Ground
Boost Pin Voltage
Feedback Pin Voltage
Power Dissipation
45V
−0.1V to 6V
−1V to VIN
VSW + 8V
−0.3V to 14V
Internally Limited
2 kV
−65°C to 150°C
4 sec, 260°C
10 sec, 240°C
75 sec, 219°C
Operating Ratings
Supply Voltage
Junction Temperature Range (TJ)
8V to 40V
−40°C to 125°C
Electrical Characteristics
Limits appearing in bold type face apply over the entire junction temperature range
of operation, −40°C to 125°C. Specifications appearing in normal type apply for TA = TJ = 25°C. Sync pin open circuited.
LM2670-3.3EP
Symbol
Parameter
Conditions
Typical
(Note 6)
Min
(Note 7)
Max
(Note 7)
Units
3.234/3.201
3.366/3.399
V
VOUT
Output Voltage
VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A
3.3
η
Efficiency
VIN = 12V, ILOAD = 3A
86
%
LM2670-5.0EP
Symbol
Parameter
Conditions
Typical
(Note 6)
Min
(Note 7)
Max
(Note 7)
Units
4.900/4.850
5.100/5.150
V
VOUT
Output Voltage
VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A
5.0
η
Efficiency
VIN = 12V, ILOAD = 3A
88
%
LM2670-12EP
Symbol
Parameter
Conditions
Typical
(Note 6)
Min
(Note 7)
Max
(Note 7)
Units
11.76/11.64
12.24/12.36
V
VOUT
Output Voltage
VIN = 15V to 40V, 100mA ≤ IOUT ≤ 3A
12
η
Efficiency
VIN = 24V, ILOAD = 3A
94
%
LM2670-ADJEP
Symbol
Parameter
Conditions
VFB
Feedback Voltage VIN = 8V to 40V, 100mA ≤ IOUT ≤ 3A
VOUT Programmed for 5V
η
Efficiency
VIN = 12V, ILOAD = 3A
Typ
(Note 6)
Min
(Note 7)
Max
(Note 7)
Units
1.21
1.186/1.174
1.234/1.246
V
88
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%
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LM2670EP Enhanced Plastic
ESD (Note 5)
Storage Temperature Range
Soldering Temperature
Wave
Infrared
Vapor Phase
Absolute Maximum Ratings (Note 4)
LM2670EP Enhanced Plastic
All Output Voltage Versions
Electrical Characteristics
Limits appearing in bold type face apply over the entire junction temperature range of operation, −40°C to 125°C.
Specifications appearing in normal type apply for TA = TJ = 25°C. Unless otherwise specified VIN=12V for the 3.3V, 5V and Adjustable versions and VIN=24V for the 12V version, Sync pin open circuited..
Symbol
Parameter
Conditions
Typ
Min
Max
Units
4.2
6
mA
100/150
μA
5.25/5.4
A
16
200
15
μA
mA
0.15
0.17/0.29
Ω
280
kHz
DEVICE PARAMETERS
IQ
Quiescent Current VFEEDBACK = 8V
For 3.3V, 5.0V, and ADJ Versions
VFEEDBACK = 15V
For 12V Versions
ISTBY
Standby Quiescent ON/OFF Pin = 0V
Current
50
ICL
Current Limit
4.5
IL
Output Leakage
Current
VIN = 40V, ON/OFF Pin = 0V
VSWITCH = 0V
VSWITCH = −1V
RDS(ON)
Switch OnResistance
ISWITCH = 3A
fO
Oscillator
Frequency
Measured at Switch Pin
D
Duty Cycle
Maximum Duty Cycle
Minimum Duty Cycle
91
0
%
%
IBIAS
Feedback Bias
Current
VFEEDBACK = 1.3V
ADJ Version Only
85
nA
VON/OFF
ON/OFF
Threshold Voltage
ION/OFF
ON/OFF Input
Current
ON/OFF Input = 0V
FSYNC
Synchronization
Frequency
VSYNC(Pin 5)=3.5V, 50% Duty Cycle
VSYNC
SYNC Threshold
Voltage
θJA
Thermal
Resistance
260
1.4
20
0.8
2.0
V
45
μA
KHz
1.4
V
65
θJA
(Note 8)
T Package, Junction to Ambient
45
θJC
(Note 9)
T Package, Junction to Case
2
θJA
S Package, Junction to Ambient
56
θJA
(Note 10)
S Package, Junction to Ambient
35
θJA
(Note 11)
S Package, Junction to Ambient
26
θJC
(Note 12)
S Package, Junction to Case
2
θJA
SD Package, Junction to Ambient
55
θJA
(Note 13)
SD Package, Junction to Ambient
(Note 14)
29
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225
400
T Package, Junction to Ambient
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3.8/3.6
Print Date/Time: 2011/03/22 16:19:19
°C/W
++
°C/W
Note 5: ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 6: Typical values are determined with TA = TJ = 25°C and represent the most likely norm.
Note 7: All limits are guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%
tested during production with TA = TJ = 25°C. All limits at temperature extremes are guaranteed via correlation using standard standard Quality Control (SQC)
methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 8: Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads in a socket, or on a
PC board with minimum copper area.
Note 9: Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ½ inch leads soldered to a PC
board containing approximately 4 square inches of (1 oz.) copper area surrounding the leads.
Note 10: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board area of 0.136 square inches (the same size as
the TO-263 package) of 1 oz. (0.0014 in. thick) copper.
Note 11: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board area of 0.4896 square inches (3.6 times the area
of the TO-263 package) of 1 oz. (0.0014 in. thick) copper.
Note 12: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board copper area of 1.0064 square inches (7.4 times
the area of the TO-263 package) of 1 oz. (0.0014 in. thick) copper. Additional copper area will reduce thermal resistance further. See the thermal model in Switchers
Made Simple® software.
Note 13: Junction to ambient thermal resistance for the 14-lead LLP mounted on a PC board copper area equal to the die attach paddle.
Note 14: Junction to ambient thermal resistance for the 14-lead LLP mounted on a PC board copper area using 12 vias to a second layer of copper equal to die
attach paddle. Additional copper area will reduce thermal resistance further. For layout recommendations, refer to Application Note AN-1187.
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LM2670EP Enhanced Plastic
Note 4: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicate conditions under which of the device
is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test condition, see the electrical
Characteristics tables.
LM2670EP Enhanced Plastic
Typical Performance Characteristics
Normalized
Output Voltage
Line Regulation
20097710
20097709
Efficiency vs Input Voltage
Efficiency vs ILOAD
20097711
20097712
Switch Current Limit
Operating Quiescent Current
20097704
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20097705
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LM2670EP Enhanced Plastic
Standby Quiescent Current
ON/OFF Threshold Voltage
20097740
20097713
ON/OFF Pin Current (Sourcing)
Switching Frequency
20097714
20097715
Feedback Pin Bias Current
20097716
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LM2670EP Enhanced Plastic
Continuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 3A
L = 33 μH, COUT = 200 μF, COUTESR = 26 mΩ
Discontinuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 500 mA
L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ
20097717
A: VSW Pin Voltage, 10 V/div.
B: Inductor Current, 1 A/div
C: Output Ripple Voltage, 20 mV/div AC-Coupled
20097718
Horizontal Time Base: 1 μs/div
A: VSW Pin Voltage, 10 V/div.
B: Inductor Current, 1 A/div
C: Output Ripple Voltage, 20 mV/div AC-Coupled
Horizontal Time Base: 1 μs//iv
Load Transient Response for Continuous Mode
VIN = 20V, VOUT = 5V
L = 33 μH, COUT = 200 μF, COUTESR = 26 mΩ
Load Transient Response for Discontinuous Mode
VIN = 20V, VOUT = 5V,
L = 10 μH, COUT = 400 μF, COUTESR = 13 mΩ
20097719
A: Output Voltage, 100 mV//div, AC-Coupled.
B: Load Current: 500 mA to 3A Load Pulse
Horizontal Time Base: 100 μs/div
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20097720
A: Output Voltage, 100 mV/div, AC-Coupled.
B: Load Current: 200 mA to 3A Load Pulse
Horizontal Time Base: 200 μs/div
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LM2670EP Enhanced Plastic
Block Diagram
20097706
* Active Inductor Patent Number 5,514,947
† Active Capacitor Patent Number 5,382,918
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LM2670EP Enhanced Plastic
SYNC
This input allows control of the switching clock frequency. If
left open-circuited the regulator will be switched at the internal
oscillator frequency, between 225KHz and 280KHz. An external clock can be used to force the switching frequency and
thereby control the output ripple frequency of the regulator.
This capability provides for consistent filtering of the output
ripple from system to system as well as precise frequency
spectrum positioning of the ripple frequency which is often
desired in communications and radio applications. This external frequency must be greater than the LM2670EP internal
oscillator frequency, which could be as high as 280KHz, to
prevent an erroneous reset of the internal ramp oscillator and
PWM control of the power switch. The ramp oscillator is reset
on the positive going edge of the sync input signal. It is recommended that the external TTL or CMOS compatible clock
(between 0V and a level greater than 3V) be ac coupled to
the sync input through a 100pf capacitor and a 1KΩ resistor
to ground at pin 5 as shown inFigure 1.
Application Hints
The LM2670EP provides all of the active functions required
for a step-down (buck) switching regulator. The internal power
switch is a DMOS power MOSFET to provide power supply
designs with high current capability, up to 3A, and highly efficient operation.
The LM2670EP is part of the SIMPLE SWITCHER family of
power converters. A complete design uses a minimum number of external components, which have been pre-determined
from a variety of manufacturers. Using either this data sheet
or a design software program called LM267X Made Simple
(version 2.0) a complete switching power supply can be designed quickly. The software is provided free of charge and
can be downloaded from National Semiconductor's Internet
site located at http://www.national.com.
SWITCH OUTPUT
This is the output of a power MOSFET switch connected directly to the input voltage. The switch provides energy to an
inductor, an output capacitor and the load circuitry under control of an internal pulse-width-modulator (PWM). The PWM
controller is internally clocked by a fixed 260KHz oscillator. In
a standard step-down application the duty cycle (Time ON/
Time OFF) of the power switch is proportional to the ratio of
the power supply output voltage to the input voltage. The voltage on pin 1 switches between Vin (switch ON) and below
ground by the voltage drop of the external Schottky diode
(switch OFF).
FEEDBACK
This is the input to a two-stage high gain amplifier, which
drives the PWM controller. It is necessary to connect pin 6 to
the actual output of the power supply to set the dc output voltage. For the fixed output devices (3.3V, 5V and 12V outputs),
a direct wire connection to the output is all that is required as
internal gain setting resistors are provided inside the
LM2670EP. For the adjustable output version two external
resistors are required to set the dc output voltage. For stable
operation of the power supply it is important to prevent coupling of any inductor flux to the feedback input.
INPUT
The input voltage for the power supply is connected to pin 2.
In addition to providing energy to the load the input voltage
also provides bias for the internal circuitry of the LM2670EP.
For guaranteed performance the input voltage must be in the
range of 8V to 40V. For best performance of the power supply
the input pin should always be bypassed with an input capacitor located close to pin 2.
ON/OFF
This input provides an electrical ON/OFF control of the power
supply. Connecting this pin to ground or to any voltage less
than 0.8V will completely turn OFF the regulator. The current
drain from the input supply when OFF is only 50μA. Pin 7 has
an internal pull-up current source of approximately 20μA and
a protection clamp zener diode of 7V to ground. When electrically driving the ON/OFF pin the high voltage level for the
ON condition should not exceed the 6V absolute maximum
limit. When ON/OFF control is not required pin 7 should be
left open circuited.
C BOOST
A capacitor must be connected from pin 3 to the switch output,
pin 1. This capacitor boosts the gate drive to the internal
MOSFET above Vin to fully turn it ON. This minimizes conduction losses in the power switch to maintain high efficiency.
The recommended value for C Boost is 0.01μF.
DAP (LLP PACKAGE)
GROUND
This is the ground reference connection for all components in
the power supply. In fast-switching, high-current applications
such as those implemented with the LM2670EP, it is recommended that a broad ground plane be used to minimize signal
coupling throughout the circuit
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The Die Attach Pad (DAP) can and should be connected to
PCB Ground plane/island. For CAD and assembly guidelines
refer
to
Application
Note
AN-1187
at
http://
power.national.com.
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LM2670EP Enhanced Plastic
DESIGN CONSIDERATIONS
20097707
FIGURE 1. Basic circuit for fixed output voltage applications.
20097708
FIGURE 2. Basic circuit for adjustable output voltage applications
Power supply design using the LM2670EP is greatly simplified by using recommended external components. A wide
range of inductors, capacitors and Schottky diodes from several manufacturers have been evaluated for use in designs
that cover the full range of capabilities (input voltage, output
voltage and load current) of the LM2670EP. A simple design
procedure using nomographs and component tables provided
in this data sheet leads to a working design with very little
effort. Alternatively, the design software, LM267X Made Simple (version 6.0), can also be used to provide instant component selection, circuit performance calculations for evaluation, a bill of materials component list and a circuit schematic.
INDUCTOR
The inductor is the key component in a switching regulator.
For efficiency the inductor stores energy during the switch ON
time and then transfers energy to the load while the switch is
OFF.
Nomographs are used to select the inductance value required
for a given set of operating conditions. The nomographs as-
The individual components from the various manufacturers
called out for use are still just a small sample of the vast array
of components available in the industry. While these components are recommended, they are not exclusively the only
components for use in a design. After a close comparison of
component specifications, equivalent devices from other
manufacturers could be substituted for use in an application.
Important considerations for each external component and an
explanation of how the nomographs and selection tables were
developed follows.
sume that the circuit is operating in continuous mode (the
current flowing through the inductor never falls to zero). The
magnitude of inductance is selected to maintain a maximum
ripple current of 30% of the maximum load current. If the ripple
current exceeds this 30% limit the next larger value is selected.
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LM2670EP Enhanced Plastic
The inductors offered have been specifically manufactured to
provide proper operation under all operating conditions of input and output voltage and load current. Several part types
are offered for a given amount of inductance. Both surface
mount and through-hole devices are available. The inductors
from each of the three manufacturers have unique characteristics.
Renco: ferrite stick core inductors; benefits are typically lowest cost and can withstand ripple and transient peak currents
above the rated value. These inductors have an external
magnetic field, which may generate EMI.
Pulse Engineering: powdered iron toroid core inductors;
these also can withstand higher than rated currents and, being toroid inductors, will have low EMI.
Coilcraft: ferrite drum core inductors; these are the smallest
physical size inductors and are available only as surface
mount components. These inductors also generate EMI but
less than stick inductors.
perature rating. Careful inspection of the manufacturer's
specification for de-rating of working voltage with temperature
is important.
INPUT CAPACITOR
Fast changing currents in high current switching regulators
place a significant dynamic load on the unregulated power
source. An input capacitor helps to provide additional current
to the power supply as well as smooth out input voltage variations.
Like the output capacitor, the key specifications for the input
capacitor are RMS current rating and working voltage. The
RMS current flowing through the input capacitor is equal to
one-half of the maximum dc load current so the capacitor
should be rated to handle this. Paralleling multiple capacitors
proportionally increases the current rating of the total capacitance. The voltage rating should also be selected to be 1.3
times the maximum input voltage. Depending on the unregulated input power source, under light load conditions the
maximum input voltage could be significantly higher than normal operation and should be considered when selecting an
input capacitor.
The input capacitor should be placed very close to the input
pin of the LM2670EP. Due to relative high current operation
with fast transient changes, the series inductance of input
connecting wires or PCB traces can create ringing signals at
the input terminal which could possibly propagate to the output or other parts of the circuitry. It may be necessary in some
designs to add a small valued (0.1μF to 0.47μF) ceramic type
capacitor in parallel with the input capacitor to prevent or minimize any ringing.
OUTPUT CAPACITOR
The output capacitor acts to smooth the dc output voltage and
also provides energy storage. Selection of an output capacitor, with an associated equivalent series resistance (ESR),
impacts both the amount of output ripple voltage and stability
of the control loop.
The output ripple voltage of the power supply is the product
of the capacitor ESR and the inductor ripple current. The capacitor types recommended in the tables were selected for
having low ESR ratings.
In addition, both surface mount tantalum capacitors and
through-hole aluminum electrolytic capacitors are offered as
solutions.
Impacting frequency stability of the overall control loop, the
output capacitance, in conjunction with the inductor, creates
a double pole inside the feedback loop. In addition the capacitance and the ESR value create a zero. These frequency
response effects together with the internal frequency compensation circuitry of the LM2670EP modify the gain and
phase shift of the closed loop system.
As a general rule for stable switching regulator circuits it is
desired to have the unity gain bandwidth of the circuit to be
limited to no more than one-sixth of the controller switching
frequency. With the fixed 260KHz switching frequency of the
LM2670EP, the output capacitor is selected to provide a unity
gain bandwidth of 40KHz maximum. Each recommended capacitor value has been chosen to achieve this result.
In some cases multiple capacitors are required either to reduce the ESR of the output capacitor, to minimize output
ripple (a ripple voltage of 1% of Vout or less is the assumed
performance condition), or to increase the output capacitance
to reduce the closed loop unity gain bandwidth (to less than
40KHz). When parallel combinations of capacitors are required it has been assumed that each capacitor is the exact
same part type.
The RMS current and working voltage (WV) ratings of the
output capacitor are also important considerations. In a typical step-down switching regulator, the inductor ripple current
(set to be no more than 30% of the maximum load current by
the inductor selection) is the current that flows through the
output capacitor. The capacitor RMS current rating must be
greater than this ripple current. The voltage rating of the output capacitor should be greater than 1.3 times the maximum
output voltage of the power supply. If operation of the system
at elevated temperatures is required, the capacitor voltage
rating may be de-rated to less than the nominal room tem-
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CATCH DIODE
When the power switch in the LM2670EP turns OFF, the current through the inductor continues to flow. The path for this
current is through the diode connected between the switch
output and ground. This forward biased diode clamps the
switch output to a voltage less than ground. This negative
voltage must be greater than −1V so a low voltage drop (particularly at high current levels) Schottky diode is recommended. Total efficiency of the entire power supply is significantly
impacted by the power lost in the output catch diode. The average current through the catch diode is dependent on the
switch duty cycle (D) and is equal to the load current times (1D). Use of a diode rated for much higher current than is
required by the actual application helps to minimize the voltage drop and power loss in the diode.
During the switch ON time the diode will be reversed biased
by the input voltage. The reverse voltage rating of the diode
should be at least 1.3 times greater than the maximum input
voltage.
BOOST CAPACITOR
The boost capacitor creates a voltage used to overdrive the
gate of the internal power MOSFET. This improves efficiency
by minimizing the on resistance of the switch and associated
power loss. For all applications it is recommended to use a
0.01μF/50V ceramic capacitor.
SYNC COMPONENTS
When synchronizing the LM2670EP with an external clock it
is recommended to connect the clock to pin 5 through a series
100pf capacitor and connect a 1KΩ resistor to ground from
pin 5. This RC network creates a short 100nS pulse on each
positive edge of the clock to reset the internal ramp oscillator.
The reset time of the oscillator is approximately 300nS.
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When the output voltage is greater than approximately 6V,
and the duty cycle at minimum input voltage is greater than
approximately 50%, the designer should exercise caution in
selection of the output filter components. When an application
designed to these specific operating conditions is subjected
to a current limit fault condition, it may be possible to observe
a large hysteresis in the current limit. This can affect the output voltage of the device until the load current is reduced
sufficiently to allow the current limit protection circuit to reset
itself.
Under current limiting conditions, the LM267x is designed to
respond in the following manner:
1. At the moment when the inductor current reaches the
current limit threshold, the ON-pulse is immediately
terminated. This happens for any application condition.
2. However, the current limit block is also designed to
momentarily reduce the duty cycle to below 50% to avoid
subharmonic oscillations, which could cause the inductor
to saturate.
3. Thereafter, once the inductor current falls below the
current limit threshold, there is a small relaxation time
during which the duty cycle progressively rises back
above 50% to the value required to achieve regulation.
If the output capacitance is sufficiently ‘large’, it may be possible that as the output tries to recover, the output capacitor
charging current is large enough to repeatedly re-trigger the
current limit circuit before the output has fully settled. This
condition is exacerbated with higher output voltage settings
because the energy requirement of the output capacitor
varies as the square of the output voltage (½CV2), thus requiring an increased charging current.
A simple test to determine if this condition might exist for a
suspect application is to apply a short circuit across the output
of the converter, and then remove the shorted output condition. In an application with properly selected external components, the output will recover smoothly.
Practical values of external components that have been experimentally found to work well under these specific operating
conditions are COUT = 47µF, L = 22µH. 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 24V and the set output voltage is
18V, then for a desired maximum current of 1.5A, the current
limit of the chosen switcher must be confirmed to be at least
3A.
FIXED OUTPUT VOLTAGE DESIGN EXAMPLE
A system logic power supply bus of 3.3V is to be generated
from a wall adapter which provides an unregulated DC voltage of 13V to 16V. The maximum load current is 2.5A.
Through-hole components are preferred.
Step 1: Operating conditions are:
Vout = 3.3V
Vin max = 16V
Iload max = 2.5A
Step 2: Select an LM2670T-3.3EP. The output voltage will
have a tolerance of
±2% at room temperature and ±3% over the full operating
temperature range.
Step 3: Use the nomograph for the 3.3V device ,Figure 3. The
intersection of the 16V horizontal line (Vin max) and the 2.5A
vertical line (Iload max) indicates that L33, a 22μH inductor, is
required.
From Table 1, L33 in a through-hole component is available
from Renco with part number RL-1283-22-43 or part number
PE-53933 from Pulse Engineering.
Step 4: Use Table 3 to determine an output capacitor. With a
3.3V output and a 22μH inductor there are four through-hole
output capacitor solutions with the number of same type capacitors to be paralleled and an identifying capacitor code
given. Table 2 provides the actual capacitor characteristics.
Any of the following choices will work in the circuit:
1 x 220μF/10V Sanyo OS-CON (code C5)
1 x 1000μF/35V Sanyo MV-GX (code C10)
1 x 2200μF/10V Nichicon PL (code C5)
1 x 1000μF/35V Panasonic HFQ (code C7)
Step 5: Use Table 4 to select an input capacitor. With 3.3V
output and 22μH there are three through-hole solutions.
These capacitors provide a sufficient voltage rating and an
rms current rating greater than 1.25A (1/2 Iload max). Again
using Table 2 for specific component characteristics the following choices are suitable:
1 x 1000μF/63V Sanyo MV-GX (code C14)
1 x 820μF/63V Nichicon PL (code C24)
1 x 560μF/50V Panasonic HFQ (code C13)
Step 6: From Table 5 a 3A Schottky diode must be selected.
For through-hole components 20V rated diodes are sufficient
and 2 part types are suitable:
1N5820
SR302
Step 7: A 0.01μF capacitor will be used for Cboost.
SIMPLE DESIGN PROCEDURE
Using the nomographs and tables in this data sheet (or use
the available design software at http://www.national.com) a
complete step-down regulator can be designed in a few simple steps.
Step 1: Define the power supply operating conditions:
Required output voltage
Maximum DC input voltage
Maximum output load current
Step 2: Set the output voltage by selecting a fixed output
LM2670EP (3.3V, 5V or 12V applications) or determine the
required feedback resistors for use with the adjustable
LM2670−ADJEP
Step 3: Determine the inductor required by using one of the
four nomographs, Figure 3 through Figure 6. Table 1 provides
a specific manufacturer and part number for the inductor.
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LM2670EP Enhanced Plastic
Step 4: Using Table 3 (fixed output voltage) or Table 6 (adjustable output voltage), determine the output capacitance
required for stable operation. Table 2 provides the specific
capacitor type from the manufacturer of choice.
Step 5: Determine an input capacitor from Table 4 for fixed
output voltage applications. Use Table 2 to find the specific
capacitor type. For adjustable output circuits select a capacitor from Table 2 with a sufficient working voltage (WV) rating
greater than Vin max, and an rms current rating greater than
one-half the maximum load current (2 or more capacitors in
parallel may be required).
Step 6: Select a diode from Table 5. The current rating of the
diode must be greater than I load max and the Reverse Voltage rating must be greater than Vin max.
Step 7: Include a 0.01μF/50V capacitor for Cboost in the design.
ADDITIONAL APPLICATION INFORMATION
LM2670EP Enhanced Plastic
ADJUSTABLE OUTPUT DESIGN EXAMPLE
In this example it is desired to convert the voltage from a two
battery automotive power supply (voltage range of 20V to
28V, typical in large truck applications) to the 14.8VDC alternator supply typically used to power electronic equipment
from single battery 12V vehicle systems. The load current required is 2A maximum. It is also desired to implement the
power supply with all surface mount components.
Step 1: Operating conditions are:
Vout = 14.8V
Vin max = 28V
Iload max = 2A
Step 2: Select an LM2670S-ADJEP. To set the output voltage
to 14.9V two resistors need to be chosen (R1 and R2 in Figure
2). For the adjustable device the output voltage is set by the
following relationship:
Using Figure 6, the intersection of 27V•μS horizontally and
the 2A vertical line (Iload max) indicates that L38 , a 68μH inductor, should be used.
From Table 1, L38 in a surface mount component is available
from Pulse Engineering with part number PE-54038S.
Step 4: Use Table 6 to determine an output capacitor. With a
14.8V output the 12.5 to 15V row is used and with a 68μH
inductor there are three surface mount output capacitor solutions. Table 2 provides the actual capacitor characteristics
based on the C Code number. Any of the following choices
can be used:
1 x 33μF/20V AVX TPS (code C6)
1 x 47μF/20V Sprague 594 (code C8)
1 x 47μF/20V Kemet T495 (code C8)
Important Note: When using the adjustable device in low
voltage applications (less than 3V output), if the nomograph,
Figure 6, selects an inductance of 22μH or less, Table 6 does
not provide an output capacitor solution. With these conditions the number of output capacitors required for stable
operation becomes impractical. It is recommended to use either a 33μH or 47μH inductor and the output capacitors from
Table 6.
Step 5: An input capacitor for this example will require at least
a 35V WV rating with an rms current rating of 1A (1/2 Iout
max). From Table 2 it can be seen that C12, a 33μF/35V capacitor from Sprague, has the required voltage/current rating
of the surface mount components.
Step 6: From Table 5 a 3A Schottky diode must be selected.
For surface mount diodes with a margin of safety on the voltage rating one of five diodes can be used:
SK34
30BQ040
30WQ04F
MBRS340
MBRD340
Step 7: A 0.01μF capacitor will be used for Cboost.
Where VFB is the feedback voltage of typically 1.21V.
A recommended value to use for R1 is 1K. In this example
then R2 is determined to be:
R2 = 11.23KΩ
The closest standard 1% tolerance value to use is 11.3KΩ
This will set the nominal output voltage to 14.88V which is
within 0.5% of the target value.
Step 3: To use the nomograph for the adjustable device, Figure 6, requires a calculation of the inductor Volt•microsecond
constant (E•T expressed in V•μS) from the following formula:
where VSAT is the voltage drop across the internal power
switch which is Rds(ON) times Iload. In this example this would
be typically 0.15Ω x 2A or 0.3V and VD is the voltage drop
across the forward bisased Schottky diode, typically 0.5V.
The switching frequency of 260KHz is the nominal value to
use to estimate the ON time of the switch during which energy
is stored in the inductor.
For this example E•T is found to be:
www.national.com
LLP PACKAGE DEVICES
The LM2670EP may be offered in the 14 lead LLP surface
mount package to allow for a significantly decreased footprint
with equivalent power dissipation compared to the TO-263.
For details on mounting and soldering specifications, refer to
Application Note AN-1187 at http://power.national.com. .
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LM2670EP Enhanced Plastic
Inductor Selection Guides
For Continuous Mode Operation
20097724
20097721
FIGURE 6. LM2670-ADJEP
FIGURE 3. LM2670-3.3EP
20097722
FIGURE 4. LM2670-5.0EP
20097723
FIGURE 5. LM2670-12EP
15
200977 Version 2 Revision 2
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www.national.com
LM2670EP Enhanced Plastic
Table 1. Inductor Manufacturer Part Numbers
Inductor
Inductance
Reference
(µH)
Number
Renco
Current
(A)
Pulse Engineering
Through Hole
Surface
Mount
Through
Hole
Surface
Mount
Coilcraft
Surface Mount
L23
33
1.35
RL-5471-7
RL1500-33
PE-53823
PE-53823S
DO3316-333
L24
22
1.65
RL-1283-22-43
RL1500-22
PE-53824
PE-53824S
DO3316-223
L25
15
2.00
RL-1283-15-43
RL1500-15
PE-53825
PE-53825S
DO3316-153
L29
100
1.41
RL-5471-4
RL-6050-100 PE-53829
PE-53829S
DO5022P-104
L30
68
1.71
RL-5471-5
RL6050-68
PE-53830
PE-53830S
DO5022P-683
L31
47
2.06
RL-5471-6
RL6050-47
PE-53831
PE-53831S
DO5022P-473
L32
33
2.46
RL-5471-7
RL6050-33
PE-53932
PE-53932S
DO5022P-333
L33
22
3.02
RL-1283-22-43
RL6050-22
PE-53933
PE-53933S
DO5022P-223
L34
15
3.65
RL-1283-15-43
—
PE-53934
PE-53934S
DO5022P-153
L38
68
2.97
RL-5472-2
—
PE-54038
PE-54038S
—
L39
47
3.57
RL-5472-3
—
PE-54039
PE-54039S
—
L40
33
4.26
RL-1283-33-43
—
PE-54040
PE-54040S
—
L41
22
5.22
RL-1283-22-43
—
PE-54041
P0841
—
L44
68
3.45
RL-5473-3
—
PE-54044
L45
10
4.47
RL-1283-10-43
—
—
—
P0845
Inductor Manufacturer Contact Numbers
Coilcraft
Coilcraft, Europe
Pulse Engineering
Phone
(800) 322-2645
FAX
(708) 639-1469
Phone
+44 1236 730 595
FAX
+44 1236 730 627
Phone
(619) 674-8100
FAX
(619) 674-8262
Pulse Engineering,
Phone
+353 93 24 107
Europe
FAX
+353 93 24 459
Renco Electronics
Phone
(800) 645-5828
FAX
(516) 586-5562
www.national.com
16
200977 Version 2 Revision 2
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—
DO5022P-103HC
LM2670EP Enhanced Plastic
Capacitor Selection Guides
Table 2. Input and Output Capacitor Codes
Capacitor
Reference
Code
Surface Mount
AVX TPS Series
C (µF) WV (V)
Irms
(A)
Sprague 594D Series
C (µF) WV (V)
Irms
(A)
Kemet T495 Series
C (µF) WV (V)
Irms
(A)
C1
330
6.3
1.15
120
6.3
1.1
100
6.3
0.82
C2
100
10
1.1
220
6.3
1.4
220
6.3
1.1
C3
220
10
1.15
68
10
1.05
330
6.3
1.1
C4
47
16
0.89
150
10
1.35
100
10
1.1
C5
100
16
1.15
47
16
1
150
10
1.1
C6
33
20
0.77
100
16
1.3
220
10
1.1
C7
68
20
0.94
180
16
1.95
33
20
0.78
C8
22
25
0.77
47
20
1.15
47
20
0.94
C9
10
35
0.63
33
25
1.05
68
20
0.94
C10
22
35
0.66
68
25
1.6
10
35
0.63
C11
15
35
0.75
22
35
0.63
C12
33
35
1
4.7
50
0.66
C13
15
50
0.9
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www.national.com
LM2670EP Enhanced Plastic
Input and Output Capacitor Codes (continued)
Through Hole
Capacitor
Sanyo OS-CON SA Series Sanyo MV-GX Series
Nichicon PL Series
Reference
C (µF) WV (V) Irms
C (µF) WV (V) Irms
C (µF) WV (V) Irms
Code
(A)
(A)
(A)
Panasonic HFQ Series
C (µF) WV (V)
Irms
(A)
C1
47
6.3
1
1000
6.3
0.8
680
10
0.8
82
35
0.4
C2
150
6.3
1.95
270
16
0.6
820
10
0.98
120
35
0.44
C3
330
6.3
2.45
470
16
0.75
1000
10
1.06
220
35
0.76
C4
100
10
1.87
560
16
0.95
1200
10
1.28
330
35
1.01
C5
220
10
2.36
820
16
1.25
2200
10
1.71
560
35
1.4
C6
33
16
0.96
1000
16
1.3
3300
10
2.18
820
35
1.62
C7
100
16
1.92
150
35
0.65
3900
10
2.36
1000
35
1.73
C8
150
16
2.28
470
35
1.3
6800
10
2.68
2200
35
2.8
C9
100
20
2.25
680
35
1.4
180
16
0.41
56
50
0.36
C10
47
25
2.09
1000
35
1.7
270
16
0.55
100
50
0.5
C11
220
63
0.76
470
16
0.77
220
50
0.92
C12
470
63
1.2
680
16
1.02
470
50
1.44
C13
680
63
1.5
820
16
1.22
560
50
1.68
C14
1000
63
1.75
1800
16
1.88
1200
50
2.22
C15
220
25
0.63
330
63
1.42
C16
220
35
0.79
1500
63
2.51
C17
560
35
1.43
C18
2200
35
2.68
C19
150
50
0.82
C20
220
50
1.04
C21
330
50
1.3
C22
100
63
0.75
C23
390
63
1.62
C24
820
63
2.22
C25
1200
63
2.51
Capacitor Manufacturer Contact Numbers
Nichicon
Panasonic
AVX
Sprague/Vishay
Sanyo
Kemet
Phone
(847) 843-7500
FAX
(847) 843-2798
Phone
(714) 373-7857
FAX
(714) 373-7102
Phone
(845) 448-9411
FAX
(845) 448-1943
Phone
(207) 324-4140
FAX
(207) 324-7223
Phone
(619) 661-6322
FAX
(619) 661-1055
Phone
(864) 963-6300
FAX
(864) 963-6521
www.national.com
18
200977 Version 2 Revision 2
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LM2670EP Enhanced Plastic
Table 3. Output Capacitors for Fixed Output Voltage Application
Output
Inductance
Voltage (V)
(µH)
3.3
5
12
Surface Mount
AVX TPS Series
Sprague 594D Series
Kemet T495 Series
No.
C Code
No.
C Code
No.
C Code
10
4
C2
3
C1
4
C4
15
4
C2
3
C1
4
C4
22
3
C2
2
C7
3
C4
33
2
C2
2
C6
2
C4
10
4
C2
4
C6
4
C4
15
3
C2
2
C7
3
C4
22
3
C2
2
C7
3
C4
33
2
C2
2
C3
2
C4
47
2
C2
1
C7
2
C4
10
4
C5
3
C6
5
C9
15
3
C5
2
C7
4
C8
22
2
C5
2
C6
3
C8
33
2
C5
1
C7
2
C8
47
2
C4
1
C6
2
C8
68
1
C5
1
C5
2
C7
100
1
C4
1
C5
1
C8
Through Hole
Output
Inductance
Voltage (V)
(µH)
3.3
5
12
Sanyo OS-CON SA
Series
Sanyo MV-GX Series
Nichicon PL Series
Panasonic HFQ
Series
No.
C Code
No.
C Code
No.
C Code
No.
C Code
10
1
C3
1
C10
1
C6
2
C6
15
1
C3
1
C10
1
C6
2
C5
22
1
C5
1
C10
1
C5
1
C7
33
1
C2
1
C10
1
C13
1
C5
10
2
C4
1
C10
1
C6
2
C5
15
1
C5
1
C10
1
C5
1
C6
22
1
C5
1
C5
1
C5
1
C5
33
1
C4
1
C5
1
C13
1
C5
47
1
C4
1
C4
1
C13
2
C3
10
2
C7
1
C5
1
C18
2
C5
15
1
C8
1
C5
1
C17
1
C5
22
1
C7
1
C5
1
C13
1
C5
33
1
C7
1
C3
1
C11
1
C4
47
1
C7
1
C3
1
C10
1
C3
68
1
C7
1
C2
1
C10
1
C3
100
1
C7
1
C2
1
C9
1
C1
No. represents the number of identical capacitor types to be connected in parallel
C Code indicates the Capacitor Reference number in Table 2 for identifying the specific component from the manufacturer.
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LM2670EP Enhanced Plastic
Table 4. Input Capacitors for Fixed Output Voltage Application
(Assumes worst case maximum input voltage and load current for a given inductance value)
Output
Inductance
Voltage (V)
(µH)
3.3
5
12
Surface Mount
AVX TPS Series
Sprague 594D Series
Kemet T495 Series
No.
C Code
No.
C Code
No.
10
2
C5
1
C7
2
C Code
C8
15
3
C9
1
C10
3
C10
22
*
*
2
C13
3
C12
33
*
*
2
C13
2
C12
10
2
C5
1
C7
2
C8
15
2
C5
1
C7
2
C8
22
3
C10
2
C12
3
C11
33
*
*
2
C13
3
C12
47
*
*
1
C13
2
C12
10
2
C7
2
C10
2
C7
15
2
C7
2
C10
2
C7
22
3
C10
2
C12
3
C10
33
3
C10
2
C12
3
C10
47
*
*
2
C13
3
C12
68
*
*
2
C13
2
C12
100
*
*
1
C13
2
C12
Through Hole
Output
Inductance
Voltage (V)
(µH)
Sanyo OS-CON SA
Series
No.
3.3
5
12
Sanyo MV-GX Series
C Code
No.
Nichicon PL Series
C Code
No.
Panasonic HFQ
Series
C Code
No.
C Code
C6
10
1
C7
2
C4
1
C5
1
15
1
C10
1
C10
1
C18
1
C6
22
*
*
1
C14
1
C24
1
C13
33
*
*
1
C12
1
C20
1
C12
10
1
C7
2
C4
1
C14
1
C6
15
1
C7
2
C4
1
C14
1
C6
22
*
*
1
C10
1
C18
1
C13
33
*
*
1
C14
1
C23
1
C13
47
*
*
1
C12
1
C20
1
C12
10
1
C9
1
C10
1
C18
1
C6
15
1
C10
1
C10
1
C18
1
C6
22
1
C10
1
C10
1
C18
1
C6
33
*
*
1
C10
1
C18
1
C6
47
*
*
1
C13
1
C23
1
C13
68
*
*
1
C12
1
C21
1
C12
100
*
*
1
C11
1
C22
1
C11
* Check voltage rating of capacitors to be greater than application input voltage.
No. represents the number of identical capacitor types to be connected in parallel
C Code indicates the Capacitor Reference number in Table 2 for identifying the specific component from the manufacturer.
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20
200977 Version 2 Revision 2
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LM2670EP Enhanced Plastic
Table 5. Schottky Diode Selection Table
Reverse
Voltage
(V)
3A
20V
SK32
30V
SK33
30WQ03F
MBRD835L
40V
SK34
30BQ040
30WQ04F
MBRS340
MBRD340
MBRB1545CT
6TQ045S
50V or
More
Surface Mount
Through Hole
5A or More
3A
5A or More
1N5820
SR302
SK35
30WQ05F
1N5821
31DQ03
1N5822
MBR340
31DQ04
SR403
MBR745
80SQ045
6TQ045
MBR350
31DQ05
SR305
Diode Manufacturer Contact Numbers
International Rectifier
Motorola
General
Semiconductor
Diodes, Inc.
Phone
(310) 322-3331
FAX
(310) 322-3332
Phone
(800) 521-6274
FAX
(602) 244-6609
Phone
(516) 847-3000
FAX
(516) 847-3236
Phone
(805) 446-4800
FAX
(805) 446-4850
21
200977 Version 2 Revision 2
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www.national.com
LM2670EP Enhanced Plastic
Table 6. Output Capacitors for Adjustable Output Voltage Applications
Output Voltage
(V)
1.21 to 2.50
2.5 to 3.75
3.75 to 5
5 to 6.25
6.25 to 7.5
7.5 to 10
10 to 12.5
12.5 to 15
15 to 20
20 to 30
30 to 37
Inductance
(µH)
Surface Mount
AVX TPS Series
Sprague 594D Series
Kemet T495 Series
No.
C Code
No.
C Code
No.
C Code
33*
7
C1
6
C2
7
C3
47*
5
C1
4
C2
5
C3
33*
4
C1
3
C2
4
C3
47*
3
C1
2
C2
3
C3
22
4
C1
3
C2
4
C3
33
3
C1
2
C2
3
C3
47
2
C1
2
C2
2
C3
22
3
C2
1
C3
3
C4
33
2
C2
2
C3
2
C4
47
2
C2
2
C3
2
C4
68
1
C2
1
C3
1
C4
22
3
C2
1
C4
3
C4
33
2
C2
1
C3
2
C4
47
1
C3
1
C4
1
C6
68
1
C2
1
C3
1
C4
33
2
C5
1
C6
2
C8
47
1
C5
1
C6
2
C8
68
1
C5
1
C6
1
C8
100
1
C4
1
C5
1
C8
33
1
C5
1
C6
2
C8
47
1
C5
1
C6
2
C8
68
1
C5
1
C6
1
C8
100
1
C5
1
C6
1
C8
33
1
C6
1
C8
1
C8
47
1
C6
1
C8
1
C8
C8
68
1
C6
1
C8
1
100
1
C6
1
C8
1
C8
33
1
C8
1
C10
2
C10
47
1
C8
1
C9
2
C10
68
1
C8
1
C9
2
C10
100
1
C8
1
C9
1
C10
33
2
C9
2
C11
2
C11
47
1
C10
1
C12
1
C11
68
1
C9
1
C12
1
C11
100
1
C9
1
C12
1
C11
10
4
C13
8
C12
15
3
C13
5
C12
2
C13
4
C12
33
1
C13
3
C12
47
1
C13
2
C12
68
1
C13
2
C12
22
No Values Available
www.national.com
22
200977 Version 2 Revision 2
Print Date/Time: 2011/03/22 16:19:19
Through Hole
Output Voltage
(V)
1.21 to 2.50
2.5 to 3.75
3.75 to 5
5 to 6.25
6.25 to 7.5
7.5 to 10
10 to 12.5
12.5 to 15
15 to 20
Inductance
(µH)
Sanyo OS-CON SA
Series
Sanyo MV-GX Series
30 to 37
Panasonic HFQ
Series
No.
C Code
No.
C Code
No.
C Code
No.
33*
2
C3
5
C1
5
C3
3
C
47*
2
C2
4
C1
3
C3
2
C5
33*
1
C3
3
C1
3
C1
2
C5
47*
1
C2
2
C1
2
C3
1
C5
22
1
C3
3
C1
3
C1
2
C5
33
1
C2
2
C1
2
C1
1
C5
47
1
C2
2
C1
1
C3
1
C5
22
1
C5
2
C6
2
C3
2
C5
33
1
C4
1
C6
2
C1
1
C5
47
1
C4
1
C6
1
C3
1
C5
68
1
C4
1
C6
1
C1
1
C5
22
1
C5
1
C6
2
C1
1
C5
33
1
C4
1
C6
1
C3
1
C5
47
1
C4
1
C6
1
C1
1
C5
68
1
C4
1
C2
1
C1
1
C5
33
1
C7
1
C6
1
C14
1
C5
47
1
C7
1
C6
1
C14
1
C5
68
1
C7
1
C2
1
C14
1
C2
100
1
C7
1
C2
1
C14
1
C2
33
1
C7
1
C6
1
C14
1
C5
47
1
C7
1
C2
1
C14
1
C5
68
1
C7
1
C2
1
C9
1
C2
100
1
C7
1
C2
1
C9
1
C2
33
1
C9
1
C10
1
C15
1
C2
47
1
C9
1
C10
1
C15
1
C2
68
1
C9
1
C10
1
C15
1
C2
100
1
C9
1
C10
1
C15
1
C2
33
1
C10
1
C7
1
C15
1
C2
47
1
C10
1
C7
1
C15
1
C2
68
1
C10
1
C7
1
C15
1
C2
100
1
C10
1
C7
1
C15
1
C2
1
C7
1
C16
1
C2
33
20 to 30
Nichicon PL Series
C Code
47
No Values
1
C7
1
C16
1
C2
68
Available
1
C7
1
C16
1
C2
100
1
C7
1
C16
1
C2
10
1
C12
1
C20
1
C10
15
1
C11
1
C20
1
C11
22
No Values
1
C11
1
C20
1
C10
33
Available
1
C11
1
C20
1
C10
47
1
C11
1
C20
1
C10
68
1
C11
1
C20
1
C10
* Set to a higher value for a practical design solution. See Applications Hints section
No. represents the number of identical capacitor types to be connected in parallel
C Code indicates the Capacitor Reference number in Table 2 for identifying the specific component from the manufacturer.
23
200977 Version 2 Revision 2
Print Date/Time: 2011/03/22 16:19:19
www.national.com
LM2670EP Enhanced Plastic
Output Capacitors for Adjustable Output Voltage Applications (continued)
LM2670EP Enhanced Plastic
Physical Dimensions inches (millimeters) unless otherwise noted
TO-263 Surface Mount Power Package
NS Package Number TS7B
TO-220 Power Package
NS Package Number TA07B
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200977 Version 2 Revision 2
Print Date/Time: 2011/03/22 16:19:19
LM2670EP Enhanced Plastic
14-Lead LLP Package
NS Package Number SRC14A
25
200977 Version 2 Revision 2
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LM2670EP Enhanced PlasticSIMPLE SWITCHER® High Efficiency 3A Step-Down Voltage
Regulator with Sync
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