LM2670S-3.3EP_技术文档

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May 2004

LM2670EP

Enhanced Plastic SIMPLE SWITCHER^®High Efficiency

3A Step-Down Voltage Regulator with Sync

General Description

Features

n Efficiency up to 94%

The LM2670EP series of regulators are monolithic inte-

grated circuits which provide all of the active functions for a

step-down (buck) switching regulator capable of driving up to

3A loads with excellent line and load regulation characteris-

n Simple and easy to design with (using off-the-shelf

external components)

n 150 mΩ DMOS output switch

n 3.3V, 5V and 12V fixed output and adjustable (1.2V to

37V ) versions

n 50µA standby current when switched OFF

>

tics. 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 adjust-

able output version.

n

2%maximum output tolerance over full line and load

conditions

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 inter-

nal 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.

n Wide input voltage range: 8V to 40V

n External Sync clock capability (280KHz to 400KHz)

n 260 KHz fixed frequency internal oscillator

Applications

>

n Simple to design, high efficiency ( 90%) step-down

switching regulators

n Efficient system pre-regulator for linear voltage

regulators

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% toler-

ance.

n Selected Military Applications

n Selected Avionics Applications

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

Ordering Information

PART NUMBER

LM2670SX-ADJEP

(Notes 1, 2)

VID PART NUMBER

V62/04628-01

TBD

NS PACKAGE NUMBER (Note 3)

TS7B

TBD

Note 1: For the following (Enhanced Plastic) versions, check for availability: LM2670SD-12EP, LM2670SD-3.3EP, LM2670SD-5.0EP, LM2670SD-

ADJEP, 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.

DS200977

www.national.com

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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2

Absolute Maximum Ratings (Note 4)

Storage Temperature Range

Soldering Temperature

Wave

−65˚C to 150˚C

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

4 sec, 260˚C

10 sec, 240˚C

75 sec, 219˚C

Infrared

Input Supply Voltage

ON/OFF Pin Voltage

Switch Voltage to Ground

Boost Pin Voltage

45V

−0.1V to 6V

−1V to V_IN

Vapor Phase

Operating Ratings

V_SW+ 8V

Supply Voltage

8V to 40V

Feedback Pin Voltage

Power Dissipation

ESD (Note 5)

−0.3V to 14V

Internally Limited

2 kV

Junction Temperature Range (T_J)

−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 T_A= T_J= 25˚C. Sync pin open

circuited.

LM2670-3.3EP

Symbol

Parameter

Conditions

Typical

(Note 6)

3.3

Min

Max

Units

(Note 7)

V_OUT

Output Voltage

Efficiency

V_IN= 8V to 40V, 100mA ≤ I_OUT≤ 3A

3.234/3.201

3.366/3.399

V

η

V_IN= 12V, I_LOAD= 3A

86

%

LM2670-5.0EP

Symbol

Parameter

Conditions

Typical

(Note 6)

5.0

Min

Max

Units

(Note 7)

V_OUT

Output Voltage

Efficiency

V_IN= 8V to 40V, 100mA ≤ I_OUT≤ 3A

4.900/4.850

5.100/5.150

V

η

V_IN= 12V, I_LOAD= 3A

88

%

LM2670-12EP

Symbol

Parameter

Conditions

Typical

(Note 6)

12

Min

Max

Units

(Note 7)

V_OUT

Output Voltage

Efficiency

V_IN= 15V to 40V, 100mA ≤ I_OUT≤ 3A

11.76/11.64

12.24/12.36

V

η

V_IN= 24V, I_LOAD= 3A

94

%

LM2670-ADJEP

Symbol

Parameter

Conditions

Typ

Min

Max

Units

(Note 6)

(Note 7)

V_FB

Feedback

V_IN= 8V to 40V, 100mA ≤ I_OUT≤ 3A

V_OUTProgrammed for 5V

1.21

88

1.186/1.174

1.234/1.246

V

Voltage

η

Efficiency

V_IN= 12V, I_LOAD= 3A

%

3

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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. Specifica-

tions appearing in normal type apply for T_A= T_J= 25˚C. Unless otherwise specified V_IN=12V for the 3.3V, 5V and Adjustable

versions and V_IN=24V for the 12V version, Sync pin open circuited..

Symbol

Parameter

Conditions

Typ

Min

Max

Units

DEVICE PARAMETERS

I_Q

Quiescent

Current

V_FEEDBACK= 8V

4.2

6

mA

For 3.3V, 5.0V, and ADJ Versions

V_FEEDBACK= 15V

For 12V Versions

I_STBY

Standby

ON/OFF Pin = 0V

Quiescent

Current

50

4.5

16

100/150

5.25/5.4

µA

A

I_CL

I_L

Current Limit

Output Leakage

Current

3.8/3.6

V_IN= 40V, ON/OFF Pin = 0V

V_SWITCH= 0V

200

15

µA

mA

V_SWITCH= −1V

R_DS(ON)Switch

On-Resistance

I_SWITCH= 3A

0.15

260

0.17/0.29

Ω

f_O

Oscillator

Measured at Switch Pin

225

280

kHz

Frequency

Duty Cycle

D

Maximum Duty Cycle

Minimum Duty Cycle

V_FEEDBACK= 1.3V

ADJ Version Only

91

0

%

I_BIAS

Feedback Bias

Current

85

nA

V_ON/OFFON/OFF

Threshold

1.4

0.8

2.0

45

V

Voltage

I_ON/OFF

F_SYNC

V_SYNC

θ_JA

ON/OFF Input

ON/OFF Input = 0V

20

µA

KHz

V

Current

Synchronization

Frequency

SYNC Threshold

Voltage

V_SYNC(Pin 5)=3.5V, 50% Duty Cycle

400

1.4

65

Thermal

T Package, Junction to Ambient

(Note 8)

Resistance

θ_JA

T Package, Junction to Ambient

(Note 9)

45

θ_JC

θ_JA

T Package, Junction to Case

S Package, Junction to Ambient

(Note 10)

2

56

˚C/W

θ_JA

S Package, Junction to Ambient

(Note 11)

35

26

S Package, Junction to Ambient

(Note 12)

θ_JC

θ_JA

S Package, Junction to Case

SD Package, Junction to Ambient

(Note 13)

2

++

55

˚C/W

θ_JA

SD Package, Junction to Ambient

(Note 14)

29

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4

All Output Voltage Versions

Electrical Characteristics ^(Continued)

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.

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 T = T = 25˚C and represent the most likely norm.

A

J

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 T = T = 25˚C. All limits at temperature extremes are guaranteed via correlation using standard standard Quality Control (SQC)

A

J

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 ¹

board with minimum copper area.

⁄

2

inch leads in a socket, or on a PC

inch leads soldered to a PC board

Note 9: Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with ¹

⁄

2

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.

5

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Typical Performance Characteristics

Normalized

Output Voltage

Line Regulation

20097709

20097710

Efficiency vs Input Voltage

Efficiency vs I_LOAD

20097711

20097712

Switch Current Limit

Operating Quiescent Current

20097704

20097705

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6

Typical Performance Characteristics (Continued)

Standby Quiescent Current

ON/OFF Threshold Voltage

20097740

20097713

ON/OFF Pin Current (Sourcing)

Switching Frequency

20097714

20097715

Feedback Pin Bias Current

20097716

7

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Typical Performance Characteristics (Continued)

Continuous Mode Switching Waveforms

V_IN= 20V, V_OUT= 5V, I_LOAD= 3A

Discontinuous Mode Switching Waveforms

V_IN= 20V, V_OUT= 5V, I_LOAD= 500 mA

L = 33 µH, C_OUT= 200 µF, C_OUTESR = 26 mΩ

L = 10 µH, C_OUT= 400 µF, C_OUTESR = 13 mΩ

20097717

A: V

Pin Voltage, 10 V/div.

20097718

SW

A: V

Pin Voltage, 10 V/div.

SW

B: Inductor Current, 1 A/div

C: Output Ripple Voltage, 20 mV/div AC-Coupled

Horizontal Time Base: 1 µs/div

Horizontal Time Base: 1 µs//iv

Load Transient Response for Continuous Mode

V_IN= 20V, V_OUT= 5V

Load Transient Response for Discontinuous Mode

V_IN= 20V, V_OUT= 5V,

L = 33 µH, C_OUT= 200 µF, C_OUTESR = 26 mΩ

L = 10 µH, C_OUT= 400 µF, C_OUTESR = 13 mΩ

20097719

A: Output Voltage, 100 mV//div, AC-Coupled.

20097720

A: Output Voltage, 100 mV/div, AC-Coupled.

B: Load Current: 500 mA to 3A Load Pulse

B: Load Current: 200 mA to 3A Load Pulse

Horizontal Time Base: 100 µs/div

Horizontal Time Base: 200 µs/div

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8

Block Diagram

20097706

* Active Inductor Patent Number 5,514,947

†

Active Capacitor Patent Number 5,382,918

9

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SYNC

Application Hints

This input allows control of the switching clock frequency. If

left open-circuited the regulator will be switched at the inter-

nal 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 regu-

lator. 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.

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 num-

ber 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 Semi-

conductor’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 exter-

nal 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 volt-

age 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 approxi-

mately 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 re-

quired 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 mini-

mizes conduction losses in the power switch to maintain high

efficiency. The recommended value for C Boost is 0.01µF.

DAP (LLP PACKAGE)

The Die Attach Pad (DAP) can and should be connected to

PCB Ground plane/island. For CAD and assembly guide-

lines refer to Application Note AN-1187 at http://

power.national.com.

GROUND

This is the ground reference connection for all components

in the power supply. In fast-switching, high-current applica-

tions such as those implemented with the LM2670EP, it is

recommended that a broad ground plane be used to mini-

mize signal coupling throughout the circuit

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10

Application Hints (Continued)

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 simpli-

fied by using recommended external components. A wide

range of inductors, capacitors and Schottky diodes from

several manufacturers have been evaluated for use in de-

signs 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 calcula-

tions for evaluation, a bill of materials component list and a

circuit schematic.

son of component specifications, equivalent devices from

other manufacturers could be substituted for use in an ap-

plication.

Important considerations for each external component and

an explanation of how the nomographs and selection tables

were developed follows.

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 re-

quired for a given set of operating conditions. The nomo-

graphs assume 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

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 compari-

11

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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 maxi-

mum 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

temperature rating. Careful inspection of the manufacturer’s

specification for de-rating of working voltage with tempera-

ture is important.

Application Hints (Continued)

maximum ripple current of 30% of the maximum load cur-

rent. If the ripple current exceeds this 30% limit the next

larger value is selected.

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 charac-

teristics.

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.

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.

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 capaci-

tance. The voltage rating should also be selected to be 1.3

times the maximum input voltage. Depending on the unregu-

lated 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.

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.

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 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.

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.

CATCH DIODE

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 fre-

quency response effects together with the internal frequency

compensation circuitry of the LM2670EP modify the gain and

phase shift of the closed loop system.

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 nega-

tive voltage must be greater than −1V so a low voltage drop

(particularly at high current levels) Schottky diode is recom-

mended. Total efficiency of the entire power supply is signifi-

cantly 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 (1-D). 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.

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 recom-

mended capacitor value has been chosen to achieve this

result.

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.

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 capaci-

tance 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.

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.

The RMS current and working voltage (WV) ratings of the

output capacitor are also important considerations. In a typi-

cal 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

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12

Required output voltage

Application Hints (Continued)

SYNC COMPONENTS

Maximum DC input voltage

Maximum output load current

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.

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 pro-

vides a specific manufacturer and part number for the induc-

tor.

ADDITIONAL APPLICATION INFORMATION

Step 4: Using Table 3 (fixed output voltage) or Table 6

(adjustable output voltage), determine the output capaci-

tance required for stable operation. Table 2 provides the

specific capacitor type from the manufacturer of choice.

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 applica-

tion designed to these specific operating conditions is sub-

jected 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.

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 capaci-

tor 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).

Under current limiting conditions, the LM267x is designed to

respond in the following manner:

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.

1. At the moment when the inductor current reaches the

current limit threshold, the ON-pulse is immediately ter-

minated. This happens for any application condition.

Step 7: Include a 0.01µF/50V capacitor for Cboost in the

design.

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.

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 volt-

age of 13V to 16V. The maximum load current is 2.5A.

Through-hole components are preferred.

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.

Step 1: Operating conditions are:

Vout = 3.3V

If the output capacitance is sufficiently ‘large’, it may be

possible that as the output tries to recover, the output ca-

pacitor 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 out-

put capacitor varies as the square of the output voltage

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.

(¹⁄ CV²), thus requiring an increased charging current.

2

Step 3: Use the nomograph for the 3.3V device ,Figure 3.

The intersection of the 16V horizontal line (V_inmax) and the

2.5A vertical line (I_loadmax) indicates that L33, a 22µH

inductor, is required.

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.

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.

Practical values of external components that have been

experimentally found to work well under these specific oper-

ating conditions are C_OUT= 47µF, L = 22µH. It should be

noted that even with these components, for a device’s cur-

rent limit of I_CLIM, the maximum load current under which the

possibility of the large current limit hysteresis can be mini-

mized is I_CLIM/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 con-

firmed to be at least 3A.

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)

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 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

Step 1: Define the power supply operating conditions:

13

www.national.com

be typically 0.15Ω x 2A or 0.3V and V_Dis 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.

Application Hints (Continued)

rms current rating greater than 1.25A (1/2 I_loadmax). 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)

For this example E•T is found to be:

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

Using Figure 6, the intersection of 27V•µS horizontally and

the 2A vertical line (I_loadmax) indicates that L38 , a 68µH

inductor, should be used.

SR302

Step 7: A 0.01µF capacitor will be used for Cboost.

From Table 1, L38 in a surface mount component is available

from Pulse Engineering with part number PE-54038S.

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 alter-

nator 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 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 so-

lutions. 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)

Step 1: Operating conditions are:

Vout = 14.8V

Vin max = 28V

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 condi-

tions 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.

Iload max = 2A

Step 2: Select an LM2670S-ADJEP. To set the output volt-

age 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:

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.

Where V_FBis 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:

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

R2 = 11.23KΩ

30BQ040

The closest standard 1% tolerance value to use is 11.3KΩ

30WQ04F

This will set the nominal output voltage to 14.88V which is

within 0.5% of the target value.

MBRS340

MBRD340

Step 3: To use the nomograph for the adjustable device,

Step 7: A 0.01µF capacitor will be used for Cboost.

Figure 6, requires

a

calculation of the inductor

Volt•microsecond constant (E•T expressed in V•µS) from

the following formula:

LLP PACKAGE DEVICES

The LM2670EP may be offered in the 14 lead LLP surface

mount package to allow for a significantly decreased foot-

print with equivalent power dissipation compared to the TO-

263. For details on mounting and soldering specifications,

refer

to

Application

Note

AN-1187

at

http://

where V_SATis the voltage drop across the internal power

switch which is R_ds(ON)times I_load. In this example this would

power.national.com. .

www.national.com

14

Inductor Selection Guides For Continuous Mode Operation

20097721

20097722

FIGURE 3. LM2670-3.3EP

FIGURE 4. LM2670-5.0EP

20097724

20097723

FIGURE 6. LM2670-ADJEP

FIGURE 5. LM2670-12EP

15

www.national.com

Inductor Selection Guides For Continuous Mode Operation (Continued)

Table 1. Inductor Manufacturer Part Numbers

Renco

Through Hole

Pulse Engineering

Coilcraft

Inductor

Reference

Number

Inductance Current

Surface

Mount

Through

Hole

Surface

Mount

Surface Mount

(µH)

(A)

L23

L24

L25

L29

L30

L31

L32

L33

L34

L38

L39

L40

L41

L44

L45

33

22

15

100

68

47

33

22

15

68

47

33

22

68

10

1.35

1.65

2.00

1.41

1.71

2.06

2.46

3.02

3.65

2.97

3.57

4.26

5.22

3.45

4.47

RL-5471-7

RL1500-33 PE-53823 PE-53823S DO3316-333

RL-1283-22-43 RL1500-22 PE-53824 PE-53824S DO3316-223

RL-1283-15-43 RL1500-15 PE-53825 PE-53825S DO3316-153

RL-5471-4

RL-5471-5

RL-5471-6

RL-5471-7

RL-6050-100 PE-53829 PE-53829S DO5022P-104

RL6050-68 PE-53830 PE-53830S DO5022P-683

RL6050-47 PE-53831 PE-53831S DO5022P-473

RL6050-33 PE-53932 PE-53932S DO5022P-333

RL-1283-22-43 RL6050-22 PE-53933 PE-53933S DO5022P-223

RL-1283-15-43

RL-5472-2

—

PE-53934 PE-53934S DO5022P-153

PE-54038 PE-54038S

PE-54039 PE-54039S

PE-54040 PE-54040S

PE-54041 P0841

—

RL-5472-3

—

RL-1283-33-43

RL-1283-22-43

RL-5473-3

—

PE-54044

—

RL-1283-10-43

P0845

DO5022P-103HC

Inductor Manufacturer Contact Numbers

Coilcraft

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

Phone +353 93 24 107

FAX +353 93 24 459

Phone (800) 645-5828

FAX (516) 586-5562

Coilcraft, Europe

Pulse Engineering

Pulse Engineering,

Europe

Renco Electronics

www.national.com

16

Capacitor Selection Guides

Table 2. Input and Output Capacitor Codes

Surface Mount

Sprague 594D Series

Irms

Capacitor

Reference

Code

AVX TPS Series

Irms

Kemet T495 Series

Irms

C (µF) WV (V) (A)

C (µF) WV (V)

(A)

C (µF) WV (V)

(A)

1.1

C1

C2

330

100

220

47

6.3

10

16

20

25

35

1.15

1.1

120

220

68

6.3

10

16

20

25

35

50

100

220

330

100

150

220

33

6.3

10

20

35

50

0.82

1.1

1.4

C3

1.15

0.89

1.15

0.77

0.94

0.77

0.63

0.66

1.05

1.35

1

1.1

C4

150

47

1.1

C5

100

33

1.1

C6

100

180

47

1.3

1.1

C7

68

1.95

1.15

1.05

1.6

0.78

0.94

0.63

0.66

C8

22

47

C9

10

33

68

C10

C11

C12

C13

22

68

10

15

0.75

1

22

33

4.7

15

0.9

17

www.national.com

Capacitor Selection Guides (Continued)

Input and Output Capacitor Codes (continued)

Through Hole

Sanyo OS-CON SA Series Sanyo MV-GX Series Nichicon PL Series

Capacitor

Reference

Code

Panasonic HFQ Series

Irms

(A)

Irms

(A)

Irms

(A)

C (µF) WV (V)

(A)

0.4

C1

C2

47

150

330

100

220

33

6.3

10

16

20

25

1

1000

270

470

560

820

1000

150

470

680

1000

220

470

680

1000

6.3

16

35

63

0.8

680

820

10

16

25

35

50

63

0.8

82

120

220

330

560

820

1000

2200

56

35

50

63

1.95

2.45

1.87

2.36

0.96

1.92

2.28

2.25

2.09

0.6

0.98

1.06

1.28

1.71

2.18

2.36

2.68

0.41

0.55

0.77

1.02

1.22

1.88

0.63

0.79

1.43

2.68

0.82

1.04

1.3

0.44

0.76

1.01

1.4

C3

0.75

0.95

1.25

1.3

1000

1200

2200

3300

3900

6800

180

C4

C5

C6

1.62

1.73

2.8

C7

100

150

100

47

0.65

1.3

C8

C9

1.4

0.36

0.5

C10

C11

C12

C13

C14

C15

C16

C17

C18

C19

C20

C21

C22

C23

C24

C25

1.7

270

100

220

470

560

1200

330

1500

0.76

1.2

470

0.92

1.44

1.68

2.22

1.42

2.51

680

1.5

820

1.75

1800

220

560

2200

150

220

330

100

0.75

1.62

2.22

2.51

390

820

1200

Capacitor Manufacturer Contact Numbers

Nichicon

Panasonic

AVX

Phone

FAX

(847) 843-7500

(847) 843-2798

(714) 373-7857

(714) 373-7102

(845) 448-9411

(845) 448-1943

(207) 324-4140

(207) 324-7223

(619) 661-6322

(619) 661-1055

(864) 963-6300

(864) 963-6521

Phone

FAX

Phone

FAX

Sprague/Vishay

Sanyo

Phone

FAX

Phone

FAX

Kemet

Phone

FAX

www.national.com

18

Capacitor Selection Guides (Continued)

Table 3. Output Capacitors for Fixed Output Voltage Application

Surface Mount

Sprague 594D

Series

Output

Voltage (V)

Inductance

(µH)

AVX TPS Series

Kemet T495 Series

No.

4

C Code

C2

No.

3

C Code

No.

4

C Code

C4

10

15

22

33

10

15

22

33

47

10

15

22

33

47

68

100

C1

C7

C6

C7

C3

C7

C6

C7

C6

C7

C6

C5

4

C2

3

4

C4

3.3

5

3

C2

2

3

C4

2

C2

2

C4

4

C2

4

C4

3

C2

2

3

C4

3

C2

2

3

C4

2

C2

2

C4

2

C2

1

2

C4

4

C5

3

5

C9

3

C5

2

4

C8

2

C5

2

3

C8

12

2

C5

1

2

C8

2

C4

1

2

C8

1

C5

1

2

C7

1

C4

1

C8

Through Hole

Sanyo MV-GX Series Nichicon PL Series

Output

Voltage (V)

Inductance Sanyo OS-CON SA

Panasonic HFQ

Series

(µH)

Series

C Code

No.

1

No.

1

C Code

C10

C5

No.

1

C Code

C6

No.

2

C Code

C6

10

15

22

33

10

15

22

33

47

10

15

22

33

47

68

100

C3

C5

C2

C4

C5

C4

C7

C8

C7

1

C6

2

C5

3.3

5

1

C5

1

C7

1

C13

C6

1

C5

2

1

2

C5

1

C5

1

C6

1

C5

1

C5

1

C5

1

C13

C18

C17

C13

C11

C10

C9

1

C5

1

C4

1

2

C3

2

1

C5

1

2

C5

1

C5

1

C5

1

C5

1

C5

12

1

C3

1

C4

1

C3

1

C3

1

C2

1

C3

1

C2

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.

19

www.national.com

Capacitor Selection Guides (Continued)

Table 4. Input Capacitors for Fixed Output Voltage Application

(Assumes worst case maximum input voltage and load current for a given inductance value)

Surface Mount

Output

Voltage (V)

Inductance

(µH)

AVX TPS Series

Sprague 594D

Series

Kemet T495 Series

No.

2

3

*

C Code

No.

1

C Code

No.

2

C Code

C8

10

15

22

33

10

15

22

33

47

10

15

22

33

47

68

100

C5

C9

*

C7

1

C10

C13

C7

3

C10

C12

C8

3.3

5

2

3

*

2

3

*

C5

C10

*

1

2

1

C7

2

C8

2

C12

C13

C10

C12

C13

3

C11

C12

C7

2

3

*

1

2

3

*

C7

C10

*

2

C7

2

3

C10

C12

12

2

3

2

3

*

2

*

1

2

Through Hole

Sanyo MV-GX Series Nichicon PL Series

Output

Voltage (V)

Inductance Sanyo OS-CON SA

Panasonic HFQ

Series

(µH)

Series

C Code

No.

1

*

No.

2

C Code

C4

No.

1

C Code

C5

No.

1

C Code

C6

10

15

22

33

10

15

22

33

47

10

15

22

33

47

68

100

C7

C10

1

C10

C14

C12

C4

1

C18

C24

C20

C14

C18

C23

C20

C18

C23

C21

C22

1

C6

3.3

5

*

1

C13

C12

C6

*

C7

*

1

*

2

1

2

C4

1

C6

1

C10

C14

C12

C10

C13

C12

C11

1

C13

C12

C6

*

1

*

1

*

C9

C10

*

1

C6

1

C6

12

1

C6

*

1

C13

C12

C11

*

1

*

1

* 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.

www.national.com

20

Capacitor Selection Guides (Continued)

Table 5. Schottky Diode Selection Table

Reverse

Voltage

(V)

Surface Mount Through Hole

3A

5A or More

3A

5A or More

20V

SK32

1N5820

SR302

30V

40V

SK33

MBRD835L

1N5821

31DQ03

1N5822

MBR340

31DQ04

SR403

30WQ03F

SK34

MBRB1545CT

6TQ045S

30BQ040

30WQ04F

MBRS340

MBRD340

SK35

MBR745

80SQ045

6TQ045

50V or

More

MBR350

31DQ05

SR305

30WQ05F

Diode Manufacturer Contact Numbers

International Rectifier Phone (310) 322-3331

(310) 322-3332

FAX

Motorola

Phone

FAX

(800) 521-6274

(602) 244-6609

(516) 847-3000

General

Phone

Semiconductor

FAX

(516) 847-3236

(805) 446-4800

(805) 446-4850

Diodes, Inc.

Phone

FAX

21

www.national.com

Capacitor Selection Guides (Continued)

Table 6. Output Capacitors for Adjustable Output Voltage Applications

Surface Mount

Sprague 594D

Series

Output Voltage Inductance

AVX TPS Series

Kemet T495 Series

(V)

(µH)

No.

7

5

4

3

4

3

2

3

2

1

3

2

1

2

1

2

1

C Code

C1

C2

C3

C2

C5

C4

C5

C6

C8

C9

C10

C9

No.

6

4

3

2

3

2

1

2

1

2

1

4

3

2

1

C Code

No.

7

5

4

3

4

3

2

3

2

1

3

2

1

2

1

2

1

2

1

2

1

8

5

4

3

2

C Code

C3

33*

47*

33*

47*

22

33

47

22

33

47

68

22

33

47

68

33

47

68

100

33

47

68

100

33

47

68

100

33

47

68

100

33

47

68

100

10

15

22

33

47

68

C2

1.21 to 2.50

2.5 to 3.75

C3

C2

C3

C2

C3

C2

C3

3.75 to 5

5 to 6.25

C2

C3

C2

C3

C4

C3

C4

C3

C4

C3

C4

C3

C4

6.25 to 7.5

7.5 to 10

10 to 12.5

12.5 to 15

15 to 20

C4

C6

C3

C4

C6

C8

C6

C8

C6

C8

C5

C8

C6

C8

C6

C8

C6

C8

C6

C8

C10

C9

C10

C11

C12

C9

C11

C12

C13

20 to 30

No Values Available

30 to 37

www.national.com

22

Capacitor Selection Guides (Continued)

Output Capacitors for Adjustable Output Voltage Applications (continued)

Through Hole

Output Voltage Inductance Sanyo OS-CON SA

Panasonic HFQ

Series

Sanyo MV-GX Series Nichicon PL Series

(V)

(µH)

Series

C Code

No.

2

1

No.

5

4

3

2

3

2

1

C Code

C1

No.

5

3

2

3

2

1

2

1

2

1

C Code

C3

No.

3

2

1

2

1

2

1

C Code

C

33*

47*

33*

47*

22

33

47

22

33

47

68

22

33

47

68

33

47

68

100

33

47

68

100

33

47

68

100

33

47

68

100

33

47

68

100

10

15

22

33

47

68

C3

C2

C3

C2

C3

C2

C5

C4

C5

C4

C7

C9

C10

1.21 to 2.50

2.5 to 3.75

C1

C3

C5

C2

C5

C2

C10

C11

C10

C1

C3

C1

3.75 to 5

5 to 6.25

C1

C3

C6

C3

C6

C1

C6

C3

C6

C1

C6

C1

C6

C3

6.25 to 7.5

7.5 to 10

10 to 12.5

12.5 to 15

15 to 20

C6

C1

C2

C1

C6

C14

C9

C6

C2

C6

C2

C9

C10

C7

C15

C16

C20

C7

No Values

C7

20 to 30

Available

C7

C12

C11

No Values

Available

30 to 37

* 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

www.national.com

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

www.national.com

24

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

14-Lead LLP Package

NS Package Number SRC14A

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT

DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or

systems which, (a) are intended for surgical implant

into the body, or (b) support or sustain life, and

whose failure to perform when properly used in

accordance with instructions for use provided in the

labeling, can be reasonably expected to result in a

significant injury to the user.

2. A critical component is any component of a life

support device or system whose failure to perform

can be reasonably expected to cause the failure of

the life support device or system, or to affect its

safety or effectiveness.

BANNED SUBSTANCE COMPLIANCE

National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products

Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification

(CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2.

National Semiconductor

Americas Customer

Support Center

National Semiconductor

Europe Customer Support Center

Fax: +49 (0) 180-530 85 86

National Semiconductor

Asia Pacific Customer

Support Center

National Semiconductor

Japan Customer Support Center

Fax: 81-3-5639-7507

Email: new.feedback@nsc.com

Tel: 1-800-272-9959

Email: europe.support@nsc.com

Deutsch Tel: +49 (0) 69 9508 6208

English Tel: +44 (0) 870 24 0 2171

Français Tel: +33 (0) 1 41 91 8790

Email: ap.support@nsc.com

Email: jpn.feedback@nsc.com

Tel: 81-3-5639-7560

www.national.com

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.


型号：	LM2670S-3.3EP
厂家：	National Semiconductor
描述：	IC 5.4 A SWITCHING REGULATOR, 280 kHz SWITCHING FREQ-MAX, PSSO7, PLASTIC, TO-263, 7 PIN, Switching Regulator or Controller 开关
文件：	总26页 (文件大小：490K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LM2670S-3.3EP [NSC]

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