National Semiconductor LM1577, LM2577 Technical data

现货库存、技术资料、百科信息、热点资讯，精彩尽在鼎好!

LM1577/LM2577
SIMPLE SWITCHER

®

Step-Up Voltage Regulator

LM1577/LM2577 SIMPLE SWITCHER Step-Up Voltage Regulator

April 2005

General Description

The LM1577/LM2577 are monolithic integrated circuits that
provide all of the power and control functions for step-up
(boost), flyback, and forward converter switching regulators.
The device is available in three different output voltage
versions: 12V, 15V, and adjustable.

Requiring a minimum number of external components, these
regulators are cost effective, and simple to use. Listed in this
data sheet are a family of standard inductors and flyback
transformers designed to work with these switching regula­tors.

Included on the chip is a 3.0A NPN switch and its associated
protection circuitry, consisting of current and thermal limiting,
and undervoltage lockout. Other features include a 52 kHz
fixed-frequency oscillator that requires no external compo­nents, a soft start mode to reduce in-rush current during
start-up, and current mode control for improved rejection of
input voltage and output load transients.

Connection Diagrams

Straight Leads

5-Lead TO-220 (T)

Features

n Requires few external components
n NPN output switches 3.0A, can stand off 65V
n Wide input voltage range: 3.5V to 40V
n Current-mode operation for improved transient

response, line regulation, and current limit

n 52 kHz internal oscillator
n Soft-start function reduces in-rush current during start-up
n Output switch protected by current limit, under-voltage

lockout, and thermal shutdown

Typical Applications

n Simple boost regulator
n Flyback and forward regulators
n Multiple-output regulator

Bent, Staggered Leads

5-Lead TO-220 (T)

Top View

Order Number LM2577T-12, LM2577T-15,

or LM2577T-ADJ

See NS Package Number T05A

SIMPLE SWITCHER®is a registered trademark of National Semiconductor Corporation.

© 2005 National Semiconductor Corporation DS011468 www.national.com

01146804

Top View

Order Number LM2577T-12 Flow LB03, LM2577T-15

Flow LB03, or LM2577T-ADJ Flow LB03

See NS Package Number T05D

01146805

Connection Diagrams (Continued)

16-Lead DIP (N) 24-Lead Surface Mount (M)

LM1577/LM2577

*No internal Connection

Order Number LM2577N-12, LM2577N-15,

See NS Package Number N16A

5-Lead Surface-Mount Package

Top View

or LM2577N-ADJ

TO-263 (S)

Top View

01146806

01146832

*No internal Connection

01146807

Top View

Order Number LM2577M-12, LM2577M-15,

or LM2577M-ADJ

See NS Package Number M24B

01146833

Side View

Order Number LM2577S-12, LM2577S-15,

or LM2577S-ADJ

See NS Package Number TS5B

4-Lead TO-3 (K)

Bottom View

Order Number LM1577K-12/883, LM1577K-15/883,

or LM1577K-ADJ/883

See NS Package Number K04A

www.national.com 2

01146808

Ordering Information

LM1577/LM2577

Temperature

Range

−40˚C ≤ T

≤ +125˚C 24-Pin Surface

A

Mount

16-Pin Molded DIP LM2577N-12 LM2577N-15 LM2577N-ADJ N16A N

5-Lead Surface
Mount

5-Straight Leads LM2577T-12 LM2577T-15 LM2577T-ADJ T05A TO-220

5-Bent Staggered LM2577T-12 LM2577T-15 LM2577T-ADJ T05D TO-220

Leads Flow LB03 Flow LB03 Flow LB03

−55˚C ≤ T

≤ +150˚C 4-Pin TO-3 LM1577K-12/883LM1577K-15/883 LM1577K-

A

Typical Application

Package

Type

Output Voltage NSC

12V 15V ADJ Package Package

Drawing

LM2577M-12 LM2577M-15 LM2577M-ADJ M24B SO

LM2577S-12 LM2577S-15 LM2577S-ADJ TS5B TO-263

K04A TO-3

ADJ/883

Note: Pin numbers shown are for TO-220 (T) package.

01146801

www.national.com3

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

Minimum ESD Rating

(C = 100 pF, R = 1.5 kΩ)2kV

please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Operating Ratings

Supply Voltage 45V

LM1577/LM2577

Output Switch Voltage 65V

Output Switch Current (Note 2) 6.0A

Power Dissipation Internally Limited

Storage Temperature Range −65˚C to +150˚C

Lead Temperature

(Soldering, 10 sec.) 260˚C

Supply Voltage 3.5V ≤ VIN≤ 40V

Output Switch Voltage 0V ≤ V

Output Switch Current I

SWITCH

Junction Temperature Range

LM1577 −55˚C ≤ T

LM2577 −40˚C ≤ T

Maximum Junction Temperature 150˚C

Electrical Characteristics—LM1577-12, LM2577-12

Specifications with standard type face are for TJ= 25˚C, and those in bold type face apply over full Operating Temperature
Range. Unless otherwise specified, V

= 5V, and I

IN

Symbol Parameter Conditions Typical Limit Limit (Limits)

SYSTEM PARAMETERS Circuit of Figure 1 (Note 6)

V

OUT

Output Voltage VIN= 5V to 10V 12.0 V

I

= 100 mA to 800 mA 11.60/11.40 11.60/11.40 V(min)

LOAD

(Note 3) 12.40/12.60 12.40/12.60 V(max)

Line Regulation VIN= 3.5V to 10V 20 mV

I

= 300 mA 50/100 50/100 mV(max)

LOAD

Load Regulation VIN=5V 20 mV

I

= 100 mA to 800 mA 50/100 50/100 mV(max)

LOAD

η Efficiency V

= 5V, I

IN

LOAD

DEVICE PARAMETERS

I

S

V

UV

Input Supply Current V

Input Supply I

FEEDBACK

I

SWITCH

V

COMP

SWITCH

= 14V (Switch Off) 7.5 mA

= 2.0A 25 mA

= 2.0V (Max Duty Cycle) 50/85 50/85 mA(max)

= 100 mA 2.90 V

Undervoltage Lockout 2.70/2.65 2.70/2.65 V(min)

f

O

V

REF

Oscillator Frequency Measured at Switch Pin 52 kHz

I

= 100 mA 48/42 48/42 kHz(min)

SWITCH

Output Reference Measured at Feedback Pin V

Voltage V

= 3.5V to 40V 12 11.76/11.64 11.76/11.64 V(min)

IN

V

= 1.0V 12.24/12.36 12.24/12.36 V(max)

COMP

Output Reference VIN= 3.5V to 40V

Voltage Line Regulator

R

FB

Feedback Pin Input 9.7 kΩ

Resistance

G

M

Error Amp I

Transconductance V

= −30 µA to +30 µA 370 µmho

COMP

= 1.0V 225/145 225/145 µmho(min)

COMP

=0.

SWITCH

LM1577-12 LM2577-12 Units

(Notes 3, 4) (Note 5)

= 800 mA 80 %

10.0/14.0 10.0/14.0 mA(max)

3.10/3.15 3.10/3.15 V(max)

56/62 56/62 kHz(max)

7mV

515/615 515/615 µmho(max)

SWITCH

J

J

≤ 60V

≤ 3.0A

≤ +150˚C

≤ +125˚C

www.national.com 4

Electrical Characteristics— LM1577-12, LM2577-12 (Continued)

Specifications with standard type face are for TJ= 25˚C, and those in bold type face apply over full Operating Temperature
Range. Unless otherwise specified, V

= 5V, and I

IN

Symbol Parameter Conditions Typical Limit Limit (Limits)

DEVICE PARAMETERS

A

VOL

Error Amp V

Voltage Gain R

= 1.1V to 1.9V 80 V/V

COMP

= 1.0 MΩ 50/25 50/25 V/V(min)

COMP

(Note 7)

Error Amplifier Upper Limit 2.4 V

Output Swing V

FEEDBACK

= 10.0V 2.2/2.0 2.2/2.0 V(min)

Lower Limit 0.3 V

Error Amplifier V

Output Current V

I

SS

Soft Start Current V

D Maximum Duty Cycle V

V

FEEDBACK

FEEDBACK

COMP

FEEDBACK

V

COMP

COMP

I

SWITCH

= 15.0V 0.40/0.55 0.40/0.55 V(max)

= 10.0V to 15.0V

= 1.0V

= 10.0V 5.0 µA

= 0V 2.5/1.5 2.5/1.5 µA(min)

= 1.5V 95 %

= 100 mA 93/90 93/90 %(min)

Switch
Transconductance

SWITCH

=0.

LM1577-12 LM2577-12 Units

(Notes 3, 4) (Note 5)

±

200 µA

±

130/±90

±

300/±400±300/±400 µA(max)

±

130/±90 µA(min)

7.5/9.5 7.5/9.5 µA(max)

12.5 A/V

LM1577/LM2577

I

L

Switch Leakage V

Current V

V

SAT

Switch Saturation I

SWITCH

Voltage V

= 65V 10 µA

SWITCH

FEEDBACK

= 15V (Switch Off) 300/600 300/600 µA(max)

= 2.0A 0.5 V

= 2.0V (Max Duty Cycle) 0.7/0.9 0.7/0.9 V(max)

COMP

NPN Switch 4.5 A

Current Limit 3.7/3.0 3.7/3.0 A(min)

5.3/6.0 5.3/6.0 A(max)

Electrical Characteristics— LM1577-15, LM2577-15

Specifications with standard type face are for TJ= 25˚C, and those in bold type face apply over full Operating Temperature
Range. Unless otherwise specified, V

= 5V, and I

IN

Symbol Parameter Conditions Typical Limit Limit (Limits)

SYSTEM PARAMETERS Circuit of Figure 2 (Note 6)

V

OUT

Output Voltage VIN= 5V to 12V 15.0 V

I

= 100 mA to 600 mA 14.50/14.25 14.50/14.25 V(min)

LOAD

(Note 3) 15.50/15.75 15.50/15.75 V(max)

Line Regulation VIN= 3.5V to 12V 20

= 300 mA mV(max)

I

LOAD

Load Regulation VIN=5V 20

I

= 100 mA to 600 mA mV(max)

LOAD

η Efficiency V

IN

= 5V, I

=0.

SWITCH

LM1577-15 LM2577-15 Units

(Notes 3, 4) (Note 5)

50/100 50/100

50/100 50/100

= 600 mA 80 %

LOAD

mV

mV

www.national.com5

Electrical Characteristics— LM1577-15, LM2577-15 (Continued)

Specifications with standard type face are for TJ= 25˚C, and those in bold type face apply over full Operating Temperature
Range. Unless otherwise specified, V

= 5V, and I

IN

Symbol Parameter Conditions Typical Limit Limit (Limits)

LM1577/LM2577

DEVICE PARAMETERS

I

S

V

UV

f

O

V

REF

R

FB

G

M

A

VOL

I

SS

D Maximum Duty V

Input Supply Current V

FEEDBACK

(Switch Off) 10.0/14.0 10.0/14.0 mA(max)

I

V

= 2.0A 25 mA

SWITCH

= 2.0V 50/85 50/85 mA(max)

COMP

(Max Duty Cycle)

Input Supply I

= 100 mA 2.90 V

SWITCH

Undervoltage 2.70/2.65 2.70/2.65 V(min)

Lockout 3.10/3.15 3.10/3.15 V(max)

Oscillator Frequency Measured at Switch Pin 52 kHz

I

= 100 mA 48/42 48/42 kHz(min)

SWITCH

Output Reference Measured at Feedback Pin V

Voltage V

= 3.5V to 40V 15 14.70/14.55 14.70/14.55 V(min)

IN

V

= 1.0V 15.30/15.45 15.30/15.45 V(max)

COMP

Output Reference VIN= 3.5V to 40V 10 mV

Voltage Line Regulation

Feedback Pin Input 12.2 kΩ

Voltage Line Regulator

Error Amp I

Transconductance V

Error Amp V

Voltage Gain R

= −30 µA to +30 µA 300 µmho

COMP

= 1.0V 170/110 170/110 µmho(min)

COMP

= 1.1V to 1.9V 65 V/V

COMP

= 1.0 MΩ 40/20 40/20 V/V(min)

COMP

(Note 7)

Error Amplifier Upper Limit 2.4 V

Output Swing V

FEEDBACK

Lower Limit 0.3 V

V

FEEDBACK

Error Amp V

Output Current V

Soft Start Current V

Cycle I

FEEDBACK

= 1.0V

COMP

FEEDBACK

V

= 0V 2.5/1.5 2.5/1.5 µA(min)

COMP

= 1.5V 95 %

COMP

= 100 mA 93/90 93/90 %(min)

SWITCH

Switch
Transconductance

=0.

SWITCH

LM1577-15 LM2577-15 Units

(Notes 3, 4) (Note 5)

= 18.0V 7.5 mA

56/62 56/62 kHz(max)

420/500 420/500 µmho(max)

= 12.0V 2.2/2.0 2.2/2.0 V(min)

= 18.0V 0.4/0.55 0.40/0.55 V(max)

= 12.0V to 18.0V

±

200 µA

±

130/±90

±

300/±400±300/±400 µA(max)

±

130/±90 µA(min)

= 12.0V 5.0 µA

7.5/9.5 7.5/9.5 µA(max)

12.5 A/V

I

L

Switch Leakage V

Current V

= 65V 10 µA

SWITCH

FEEDBACK

= 18.0V 300/600 300/600 µA(max)

(Switch Off)

V

SAT

Switch Saturation I

Voltage V

= 2.0A 0.5 V

SWITCH

= 2.0V 0.7/0.9 0.7/0.9 V(max)

COMP

(Max Duty Cycle)

www.national.com 6

Electrical Characteristics— LM1577-15, LM2577-15 (Continued)

Specifications with standard type face are for TJ= 25˚C, and those in bold type face apply over full Operating Temperature
Range. Unless otherwise specified, V

= 5V, and I

IN

SWITCH

=0.

LM1577-15 LM2577-15 Units

Symbol Parameter Conditions Typical Limit Limit (Limits)

(Notes 3, 4) (Note 5)

DEVICE PARAMETERS

NPN Switch V

= 2.0V 4.3 A

COMP

Current Limit 3.7/3.0 3.7/3.0 A(min)

5.3/6.0 5.3/6.0 A(max)

Electrical Characteristics— LM1577-ADJ, LM2577-ADJ

Specifications with standard type face are for TJ= 25˚C, and those in bold type face apply over full Operating Temperature
Range. Unless otherwise specified, V

= 5V, V

IN

FEEDBACK

Symbol Parameter Conditions Typical Limit Limit (Limits)

SYSTEM PARAMETERS Circuit of Figure 3 (Note 6)

V

OUT

Output Voltage VIN= 5V to 10V 12.0 V

I

= 100 mA to 800 mA 11.60/11.40 11.60/11.40 V(min)

LOAD

(Note 3) 12.40/12.60 12.40/12.60 V(max)

∆V

/ Line Regulation VIN= 3.5V to 10V 20 mV

OUT

∆V

IN

∆V

/ Load Regulation VIN=5V 20 mV

OUT

∆I

LOAD

η Efficiency V

I

= 300 mA 50/100 50/100 mV(max)

LOAD

I

= 100 mA to 800 mA 50/100 50/100 mV(max)

LOAD

= 5V, I

IN

LOAD

DEVICE PARAMETERS

I

S

V

UV

Input Supply Current V

Input Supply I

FEEDBACK

I

SWITCH

V

COMP

SWITCH

= 1.5V (Switch Off) 7.5 mA

= 2.0A 25 mA

= 2.0V (Max Duty Cycle) 50/85 50/85 mA(max)

= 100 mA 2.90 V

Undervoltage Lockout 2.70/2.65 2.70/2.65 V(min)

f

O

V

∆V

∆V

I

B

REF

REF

IN

Oscillator Frequency Measured at Switch Pin 52 kHz

I

= 100 mA 48/42 48/42 kHz(min)

SWITCH

Reference Measured at Feedback Pin V

Voltage V

= 3.5V to 40V 1.230 1.214/1.206 1.214/1.206 V(min)

IN

V

= 1.0V 1.246/1.254 1.246/1.254 V(max)

COMP

/ Reference Voltage VIN= 3.5V to 40V 0.5 mV

Line Regulation

Error Amp V

= 1.0V 100 nA

COMP

Input Bias Current 300/800 300/800 nA(max)

G

M

A

VOL

Error Amp I

Transconductance V

Error Amp V

Voltage Gain R

= −30 µA to +30 µA 3700 µmho

COMP

= 1.0V 2400/1600 2400/1600 µmho(min)

COMP

= 1.1V to 1.9V 800 V/V

COMP

= 1.0 MΩ (Note 7) 500/250 500/250 V/V(min)

COMP

=V

REF

, and I

SWITCH

=0.

LM1577-ADJ LM2577-ADJ Units

(Notes 3, 4) (Note 5)

= 800 mA 80 %

10.0/14.0 10.0/14.0 mA(max)

3.10/3.15 3.10/3.15 V(max)

56/62 56/62 kHz(max)

4800/5800 4800/5800 µmho(max)

LM1577/LM2577

www.national.com7

Electrical Characteristics— LM1577-ADJ, LM2577-ADJ (Continued)

Specifications with standard type face are for TJ= 25˚C, and those in bold type face apply over full Operating Temperature
Range. Unless otherwise specified, V

= 5V, V

IN

FEEDBACK

Symbol Parameter Conditions Typical Limit Limit (Limits)

LM1577/LM2577

DEVICE PARAMETERS

Error Amplifier Upper Limit 2.4 V

Output Swing V

FEEDBACK

Lower Limit 0.3 V

V

FEEDBACK

Error Amp V

Output Current V

I

SS

Soft Start Current V

D Maximum Duty Cycle V

∆I

∆V

I

L

/ Switch 12.5 A/V

SWITCH

COMP

Transconductance

Switch Leakage V

Current V

V

SAT

Switch Saturation I

Voltage V

NPN Switch V

FEEDBACK

COMP

FEEDBACK

V

COMP

COMP

I

SWITCH

SWITCH

FEEDBACK

SWITCH

COMP

COMP

Current Limit 3.7/3.0 3.7/3.0 A(min)

THERMAL PARAMETERS (All Versions)

θ

JA

θ

JC

θ

JA

θ

JC

θ

JA

Thermal Resistance K Package, Junction to Ambient 35

K Package, Junction to Case 1.5

T Package, Junction to Ambient 65

T Package, Junction to Case 2

N Package, Junction to 85

Ambient (Note 8)

θ

JA

M Package, Junction 100

to Ambient (Note 8)

θ

JA

S Package, Junction to 37

Ambient (Note 9)

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions the device is intended to
be functional, but device parameter specifications may not be guaranteed under these conditions. For guaranteed specifications and test conditions, see the
Electrical Characteristics.

Note 2: Due to timing considerations of the LM1577/LM2577 current limit circuit, output current cannot be internally limited when the LM1577/LM2577 is used as
a step-up regulator. To prevent damage to the switch, its current must be externally limited to 6.0A. However, output current is internally limited when the
LM1577/LM2577 is used as a flyback or forward converter regulator in accordance to the Application Hints.

Note 3: All limits guaranteed at room temperature (standard type face) and at temperature extremes (boldface type). All limits are used to calculate Outgoing Quality
Level, and are 100% production tested.

Note 4: A military RETS electrical test specification is available on request. At the time of printing, the LM1577K-12/883, LM1577K-15/883, and LM1577K-ADJ/883
RETS specifications complied fully with the boldface limits in these columns. The LM1577K-12/883, LM1577K-15/883, and LM1577K-ADJ/883 may also be procured
to Standard Military Drawing specifications.

Note 5: All limits guaranteed at room temperature (standard type face) and at temperature extremes (boldface type). All room temperature limits are 100%
production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods.

Note 6: External components such as the diode, inductor, input and output capacitors can affect switching regulator performance. When the LM1577/LM2577 is
used as shown in the Test Circuit, system performance will be as specified by the system parameters.

Note 7: A 1.0 MΩ resistor is connected to the compensation pin (which is the error amplifier’s output) to ensure accuracy in measuring A
this pin’s load resistance should be ≥10 MΩ, resulting in A

= 1.0V 2.2/2.0 2.2/2.0 V(min)

= 1.5V 0.40/0.55 0.40/0.55 V(max)

= 1.0V to 1.5V

= 1.0V

= 1.0V 5.0 µA

= 0V 2.5/1.5 2.5/1.5 µA(min)

= 1.5V 95 %

= 100 mA 93/90 93/90 %(min)

= 65V 10 µA

= 1.5V (Switch Off) 300/600 300/600 µA(max)

= 2.0A 0.5 V

= 2.0V (Max Duty Cycle) 0.7/0.9 0.7/0.9 V(max)

= 2.0V 4.3 A

that is typically twice the guaranteed minimum limit.

VOL

=V

REF

, and I

=0.

SWITCH

LM1577-ADJ LM2577-ADJ Units

(Notes 3, 4) (Note 5)

±

200 µA

±

130/±90

±

300/±400±300/±400 µA(max)

±

130/±90 µA(min)

7.5/9.5 7.5/9.5 µA(max)

5.3/6.0 5.3/6.0 A(max)

. In actual applications,

VOL

˚C/W

www.national.com 8

Electrical Characteristics— LM1577-ADJ, LM2577-ADJ (Continued)

Note 8: Junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. Additional copper area will lower thermal

resistance further. See thermal model in “Switchers Made Simple” software.

Note 9: If the TO-263 package is used, the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the package. Using

0.5 square inches of copper area, θ

is 50˚C/W; with 1 square inch of copper area, θJAis 37˚C/W; and with 1.6 or more square inches of copper area, θJAis 32˚C/W.

JA

Typical Performance Characteristics

LM1577/LM2577

Reference Voltage

vs Temperature

Reference Voltage

vs Temperature

Reference Voltage

vs Temperature

01146834 01146835

∆ Reference Voltage

vs Supply Voltage

∆ Reference Voltage

vs Supply Voltage

01146836 01146837

∆ Reference Voltage

vs Supply Voltage

01146838

01146839

www.national.com9

Typical Performance Characteristics (Continued)

LM1577/LM2577

Error Amp Transconductance

vs Temperature

Error Amp Transconductance

vs Temperature

01146840

Error Amp Transconductance

vs Temperature

01146841

Error Amp Voltage

Gain vs Temperature

Error Amp Voltage

Gain vs Temperature

01146842

01146843

Error Amp Voltage

Gain vs Temperature

01146844 01146845

www.national.com 10

Typical Performance Characteristics (Continued)

LM1577/LM2577

Quiescent Current

vs Temperature

Current Limit

vs Temperature

Quiescent Current

vs Switch Current

01146846 01146847

Current Limit Response

Time vs Overdrive

Switch Saturation Voltage

vs Switch Current

01146848

01146850

01146849

Switch Transconductance

vs Temperature

01146851

www.national.com11

Typical Performance Characteristics (Continued)

LM1577/LM2577

Feedback Pin Bias

Current vs Temperature

Maximum Power Dissipation

(TO-263) (Note 9)

01146852

Oscillator Frequency

vs Temperature

01146853

01146831

www.national.com 12

LM1577-12, LM2577-12 Test Circuit

LM1577/LM2577

L = 415-0930 (AIE)

D = any manufacturer

= Sprague Type 673D

C

OUT

Electrolytic 680 µF, 20V

Note: Pin numbers shown are for TO-220 (T) package

FIGURE 1. Circuit Used to Specify System Parameters for 12V Versions

LM1577-15, LM2577-15 Test Circuit

L = 415-0930 (AIE)

D = any manufacturer

= Sprague Type 673D

C

OUT

Electrolytic 680 µF, 20V

Note: Pin numbers shown are for TO-220 (T) package

01146830

01146826

FIGURE 2. Circuit Used to Specify System Parameters for 15V Versions

www.national.com13

LM1577-ADJ, LM2577-ADJ Test Circuit

LM1577/LM2577

L = 415-0930 (AIE)

D = any manufacturer

= Sprague Type 673D

C

OUT

Electrolytic 680 µF, 20V

R1 = 48.7k in series with 511Ω (1%)

R2 = 5.62k (1%)

Note: Pin numbers shown are for TO-220 (T) package

FIGURE 3. Circuit Used to Specify System Parameters for ADJ Versions

Application Hints

01146809

Note: Pin numbers shown are for TO-220 (T) package

*Resistors are internal to LM1577/LM2577 for 12V and 15V versions.

FIGURE 4. LM1577/LM2577 Block Diagram and Boost Regulator Application

www.national.com 14

01146810

Application Hints (Continued)

STEP-UP (BOOST) REGULATOR

Figure 4 shows the LM1577-ADJ/LM2577-ADJ used as a
Step-Up Regulator. This is a switching regulator used for
producing an output voltage greater than the input supply
voltage. The LM1577-12/LM2577-12 and LM1577-15/
LM2577-15 can also be used for step-up regulators with 12V
or 15V outputs (respectively), by tying the feedback pin
directly to the regulator output.

A basic explanation of how it works is as follows. The
LM1577/LM2577 turns its output switch on and off at a
frequency of 52 kHz, and this creates energy in the inductor
(L). When the NPN switch turns on, the inductor current
charges up at a rate of V
When the switch turns off, the lower end of the inductor flies
above V

, discharging its current through diode (D) into the

IN

output capacitor (C
energy stored in the inductor during the switch on time is
transferred to the output during the switch off time. The
output voltage is controlled by the amount of energy trans­ferred which, in turn, is controlled by modulating the peak
inductor current. This is done by feeding back a portion of
the output voltage to the error amp, which amplifies the
difference between the feedback voltage and a 1.230V ref­erence. The error amp output voltage is compared to a
voltage proportional to the switch current (i.e., inductor cur­rent during the switch on time).

The comparator terminates the switch on time when the two
voltages are equal, thereby controlling the peak switch cur­rent to maintain a constant output voltage.

Voltage and current waveforms for this circuit are shown in

Figure 5, and formulas for calculating them are given in
Figure 6.

/L, storing current in the inductor.

IN

) at a rate of (V

OUT

OUT−VIN

)/L. Thus,

Duty Cycle D

Average
Inductor

I

IND(AVE)

Current

Inductor
Current Ripple

Peak Inductor
Current

Peak Switch
Current

∆I

I

IND(PK)

I

SW(PK)

IND

Switch
Voltage When

V

SW(OFF)

Off

Diode
Reverse

V

R

Voltage

Average
Diode Current

Peak Diode
Current

I

D(AVE)

I

D(PK)

Power
Dissipation of

P

D

LM1577/2577

VF= Forward Biased Diode Voltage
I

= Output Load Current

LOAD

FIGURE 6. Step-Up Regulator Formulas

V

OUT+VF

V

OUT−VSAT

I

LOAD

LM1577/LM2577

01146811

FIGURE 5. Step-Up Regulator Waveforms

STEP-UP REGULATOR DESIGN PROCEDURE

The following design procedure can be used to select the
appropriate external components for the circuit in Figure 4,
based on these system requirements.

Given:

V
V
I

LOAD(max)

= Minimum input supply voltage

IN (min)

= Regulated output voltage

OUT

= Maximum output load current

Before proceeding any further, determine if the LM1577/
LM2577 can provide these values of V

OUT

and I

LOAD(max)

when operating with the minimum value of VIN. The upper
limits for V

OUT

and I

LOAD(max)

are given by the following

equations.

≤ 60V

V

OUT

and V

OUT

≤ 10xV

IN(min)

These limits must be greater than or equal to the values
specified in this application.

1. Inductor Selection (L)

A. Voltage Options:

1. For 12V or 15V output

From Figure 7 (for 12V output) or Figure 8 (for 15V
output), identify inductor code for region indicated by

V

IN (min)

and I

LOAD (max)

. The shaded region indicates con-

www.national.com15

Application Hints (Continued)

ditions for which the LM1577/LM2577 output switch
would be operating beyond its switch current rating. The
minimum operating voltage for the LM1577/LM2577 is

3.5V.

LM1577/LM2577

From here, proceed to step C.

2. For Adjustable version

Preliminary calculations:

The inductor selection is based on the calculation of the
following three parameters:

, the maximum switch duty cycle (0 ≤ D ≤ 0.9):

D

(max)

where VF= 0.5V for Schottky diodes and 0.8V for fast
recovery diodes (typically);

T, the product of volts x time that charges the inductor:

E

•

I

, the average inductor current under full load;

IND,DC

1. Find the lowest value inductor that is greater than L

2. Find where E
if it has an L or H prefix. If E

T intersects this inductor value to determine

•

T intersects both the L and H

•

regions, select the inductor with an H prefix.

01146827

FIGURE 7. LM2577-12 Inductor Selection Guide

MIN

.

B. Identify Inductor Value:

1. From Figure 9, identify the inductor code for the
region indicated by the intersection of E

T and I

•

IND,DC

This code gives the inductor value in microhenries. The
L or H prefix signifies whether the inductor is rated for a
maximum E

2. If D

Tof90V•µs (L) or 250 V•µs (H).

•

<

0.85, go on to step C. If D ≥ 0.85, then calculate
the minimum inductance needed to ensure the switching
regulator’s stability:

If L

is smaller than the inductor value found in step B1, go

MIN

on to step C. Otherwise, the inductor value found in step B1
is too low; an appropriate inductor code should be obtained
from the graph as follows:

.

01146828

FIGURE 8. LM2577-15 Inductor Selection Guide

www.national.com 16

Application Hints (Continued)

LM1577/LM2577

Note: These charts assume that the inductor ripple current inductor is approximately 20% to 30% of the average inductor current (when the regulator is under

full load). Greater ripple current causes higher peak switch currents and greater output ripple voltage; lower ripple current is achieved with larger-value
inductors. The factor of 20 to 30% is chosen as a convenient balance between the two extremes.

01146812

FIGURE 9. LM1577-ADJ/LM2577-ADJ Inductor Selection Graph

C. Select an inductor from the table of Figure 10 which

cross-references the inductor codes to the part numbers
of three different manufacturers. Complete specifications
for these inductors are available from the respective
manufacturers. The inductors listed in this table have the
following characteristics:

AIE: ferrite, pot-core inductors; Benefits of this type are
low electro-magnetic interference (EMI), small physical
size, and very low power dissipation (core loss). Be
careful not to operate these inductors too far beyond their
maximum ratings for E

T and peak current, as this will

•

saturate the core.
Pulse: powdered iron, toroid core inductors; Benefits are

low EMI and ability to withstand E

T and peak current

•

above rated value better than ferrite cores.
Renco: ferrite, bobbin-core inductors; Benefits are low

cost and best ability to withstand E

T and peak current

•

above rated value. Be aware that these inductors gener­ate more EMI than the other types, and this may interfere
with signals sensitive to noise.

www.national.com17

Application Hints (Continued)

Inductor Manufacturer’s Part Number

Code Schott Pulse Renco

LM1577/LM2577

L47 67126980 PE - 53112 RL2442

L68 67126990 PE - 92114 RL2443

L100 67127000 PE - 92108 RL2444

L150 67127010 PE - 53113 RL1954

L220 67127020 PE - 52626 RL1953

L330 67127030 PE - 52627 RL1952

L470 67127040 PE - 53114 RL1951

L680 67127050 PE - 52629 RL1950

H150 67127060 PE - 53115 RL2445

H220 67127070 PE - 53116 RL2446

H330 67127080 PE - 53117 RL2447

H470 67127090 PE - 53118 RL1961

H680 67127100 PE - 53119 RL1960

H1000 67127110 PE - 53120 RL1959

H1500 67127120 PE - 53121 RL1958

H2200 67127130 PE - 53122 RL2448

Schott Corp., [phone]
1000 Parkers Lake Rd., Wayzata, MN 55391
Pulse Engineering, [phone]
P.O. Box 12235, San Diego, CA 92112
Renco Electronics Inc., [phone]
60 Jeffryn Blvd. East, Deer Park, NY 11729

FIGURE 10. Table of Standardized Inductors and

Manufacturer’s Part Numbers

2. Compensation Network (R
) Selection

(C

OUT

and CCform a pole-zero compensation network that

R

C

stabilizes the regulator. The values of R
dependant on the regulator voltage gain, I

. The following procedure calculates values for RC,CC,

C

OUT

and C

that ensure regulator stability. Be aware that this

OUT

procedure doesn’t necessarily result in R

) and Output Capacitor

C,CC

and CCare mainly

C

LOAD(max)

and CCthat pro-

C

vide optimum compensation. In order to guarantee optimum
compensation, one of the standard procedures for testing
loop stability must be used, such as measuring V
sient response when pulsing I

A. First, calculate the maximum value for R

(see Figure 15).

LOAD

.

C

Select a resistor less than or equal to this value, and it
should also be no greater than 3 kΩ.

B. Calculate the minimum value for C

using the following

OUT

two equations.

, L and

OUT

tran-

C. Calculate the minimum value of C

.

C

The compensation capacitor is also part of the soft start
circuitry. When power to the regulator is turned on, the
switch duty cycle is allowed to rise at a rate controlled by this
capacitor (with no control on the duty cycle, it would imme­diately rise to 90%, drawing huge currents from the input
power supply). In order to operate properly, the soft start
circuit requires C

≥ 0.22 µF.

C

The value of the output filter capacitor is normally large
enough to require the use of aluminum electrolytic capaci­tors. Figure 11 lists several different types that are recom­mended for switching regulators, and the following param­eters are used to select the proper capacitor.

Working Voltage (WVDC): Choose a capacitor with a work­ing voltage at least 20% higher than the regulator output
voltage.

Ripple Current: This is the maximum RMS value of current
that charges the capacitor during each switching cycle. For
step-up and flyback regulators, the formula for ripple current
is

Choose a capacitor that is rated at least 50% higher than this
value at 52 kHz.

Equivalent Series Resistance (ESR) : This is the primary
cause of output ripple voltage, and it also affects the values

and CCneeded to stabilize the regulator. As a result,

of R

C

the preceding calculations for C

and RCare only valid if

C

ESR doesn’t exceed the maximum value specified by the
following equations.

Select a capacitor with ESR, at 52 kHz, that is less than or
equal to the lower value calculated. Most electrolytic capaci­tors specify ESR at 120 Hz which is 15% to 30% higher than
at 52 kHz. Also, be aware that ESR increases by a factor of
2 when operating at −20˚C.

In general, low values of ESR are achieved by using large
value capacitors (C ≥ 470 µF), and capacitors with high
WVDC, or by paralleling smaller-value capacitors.

The larger of these two values is the minimum value that
ensures stability.

www.national.com 18

LM1577/LM2577

Application Hints (Continued)

3. Output Voltage Selection (R1 and R2)

This section is for applications using the LM1577-ADJ/
LM2577-ADJ. Skip this section if the LM1577-12/LM2577-12
or LM1577-15/LM2577-15 is being used.

With the LM1577-ADJ/LM2577-ADJ, the output voltage is
given by

= 1.23V (1 + R1/R2)

V

OUT

Resistors R1 and R2 divide the output down so it can be
compared with the LM1577-ADJ/LM2577-ADJ internal

1.23V reference. For a given desired output voltage V
select R1 and R2 so that

4. Input Capacitor Selection (CIN)

The switching action in the step-up regulator causes a trian­gular ripple current to be drawn from the supply source. This
in turn causes noise to appear on the supply voltage. For
proper operation of the LM1577, the input voltage should be
decoupled. Bypassing the Input Voltage pin directly to
ground with a good quality, low ESR, 0.1 µF capacitor (leads
as short as possible) is normally sufficient.

Cornell Dublier — Types 239, 250, 251, UFT,
300, or 350

P.O. Box 128, Pickens, SC 29671
[phone]

Nichicon —Types PF, PX, or PZ

927 East Parkway,
Schaumburg, IL 60173
[phone]

Sprague —Types 672D, 673D, or 674D

Box 1, Sprague Road,
Lansing, NC 28643
[phone]

United Chemi-Con — Types LX, SXF, or SXJ

9801 West Higgins Road,
Rosemont, IL 60018
[phone]

FIGURE 11. Aluminum Electrolytic Capacitors

Recommended for Switching Regulators

OUT

If the LM1577 is located far from the supply source filter
capacitors, an additional large electrolytic capacitor (e.g.
47 µF) is often required.

5. Diode Selection (D)

The switching diode used in the boost regulator must with­stand a reverse voltage equal to the circuit output voltage,
and must conduct the peak output current of the LM2577. A
suitable diode must have a minimum reverse breakdown
voltage greater than the circuit output voltage, and should be
rated for average and peak current greater than I

,

and I
in switching regulators. Their low forward voltage drop allows

. Schottky barrier diodes are often favored for use

D(PK)

LOAD(max)

higher regulator efficiency than if a (less expensive) fast
recovery diode was used. See Figure 12 for recommended
part numbers and voltage ratings of 1A and 3A diodes.

V

OUT

Schottky Fast Recovery

(max) 1A 3A 1A 3A

20V 1N5817 1N5820

MBR120P MBR320P

1N5818 1N5821

30V MBR130P MBR330P

11DQ03 31DQ03

1N5819 1N5822

40V MBR140P MBR340P

11DQ04 31DQ04

MBR150 MBR350 1N4933

50V 11DQ05 31DQ05 MUR105

1N4934 MR851

100V HER102 30DL1

MUR110 MR831

10DL1 HER302

FIGURE 12. Diode Selection Chart

BOOST REGULATOR CIRCUIT EXAMPLE

By adding a few external components (as shown in Figure

13), the LM2577 can be used to produce a regulated output

voltage that is greater than the applied input voltage. Typical
performance of this regulator is shown in Figure 14 and
Figure 15. The switching waveforms observed during the
operation of this circuit are shown in Figure 16.

www.national.com19

Application Hints (Continued)

LM1577/LM2577

Note: Pin numbers shown are for TO-220 (T) package.

FIGURE 13. Step-up Regulator Delivers 12V from a 5V Input

FIGURE 14. Line Regulation (Typical) of Step-Up Regulator of Figure 13

01146813

01146814

A: Output Voltage Change, 100 mV/div. (AC-coupled)

01146815

B: Load current, 0.2 A/div

Horizontal: 5 ms/div

FIGURE 15. Load Transient Response of Step-Up

Regulator of Figure 13

www.national.com 20

A: Switch pin voltage, 10 V/div

01146816

B: Switch pin current, 2 A/div

C: Inductor current, 2 A/div

D: Output ripple voltage, 100 mV/div (AC-coupled)

Horizontal: 5 µs/div

FIGURE 16. Switching Waveforms of Step-Up

Regulator of Figure 13

Application Hints (Continued)

FLYBACK REGULATOR

A Flyback regulator can produce single or multiple output
voltages that are lower or greater than the input supply
voltage. Figure 18 shows the LM1577/LM2577 used as a
flyback regulator with positive and negative regulated out­puts. Its operation is similar to a step-up regulator, except the
output switch contols the primary current of a flyback trans­former. Note that the primary and secondary windings are
out of phase, so no current flows through secondary when
current flows through the primary. This allows the primary to
charge up the transformer core when the switch is on. When
the switch turns off, the core discharges by sending current
through the secondary, and this produces voltage at the
outputs. The output voltages are controlled by adjusting the
peak primary current, as described in the step-up regulator
section.

Voltage and current waveforms for this circuit are shown in

Figure 17, and formulas for calculating them are given in
Figure 19.

FLYBACK REGULATOR DESIGN PROCEDURE

1. Transformer Selection

A family of standardized flyback transformers is available for
creating flyback regulators that produce dual output volt­ages, from
20lists these transformers with the input voltage, output
voltages and maximum load current they are designed for.

±

10V to±15V, as shown in Figure 18. Figure

A. First, calculate the maximum value for R

Where∑I

LOAD(max)

is the sum of the load current (magni-

.

C

tude) required from both outputs. Select a resistor less than
or equal to this value, and no greater than 3 kΩ.

∑

C

B. Calculate the minimum value for

OUT

(sum of C

OUT

at both outputs) using the following two equations.

The larger of these two values must be used to ensure
regulator stability.

LM1577/LM2577

2. Compensation Network (C
Output Capacitor (C

) Selection

OUT

C,RC

) and

As explained in the Step-Up Regulator Design Procedure,
C

C,RC

and C

must be selected as a group. The following

OUT

procedure is for a dual output flyback regulator with equal
turns ratios for each secondary (i.e., both output voltages
have the same magnitude). The equations can be used for a
single output regulator by changing

I

LOAD(max)

to I

LOAD(max)

∑

in the following equations.

01146817

FIGURE 17. Flyback Regulator Waveforms

www.national.com21

Application Hints (Continued)

LM1577/LM2577

T1 = Pulse Engineering, PE-65300

D1, D2 = 1N5821

FIGURE 18. LM1577-ADJ/LM2577-ADJ Flyback Regulator with±Outputs

01146818

www.national.com 22

Application Hints (Continued)

Duty Cycle D

LM1577/LM2577

Primary Current Variation

Peak Primary Current

I

Switch Voltage when Off

V

SW(OFF)

Diode Reverse Voltage V

Average Diode Current I

D(AVE)

Peak Diode Current

I

D(PK)

Short Circuit Diode Current

Power Dissipation of
LM1577/LM2577

∆I

P(PK)

P

P

+

R

D

V

OUT

N(V

I

LOAD

−

V

SAT

)

IN

FIGURE 19. Flyback Regulator Formulas

C. Calculate the minimum value of C

D. Calculate the maximum ESR of the +V

C

and −V

OUT

OUT

output capacitors in parallel.

This formula can also be used to calculate the maximum
ESR of a single output regulator.

At this point, refer to this same section in the Step-Up
Regulator Design Procedurefor more information regard­ing the selection of C

OUT

.

3. Output Voltage Selection

This section is for applications using the LM1577-ADJ/
LM2577-ADJ. Skip this section if the LM1577-12/LM2577-12
or LM1577-15/LM2577-15 is being used.

With the LM1577-ADJ/LM2577-ADJ, the output voltage is
given by

01146878

= 1.23V (1 + R1/R2)

V

OUT

Resistors R1 and R2 divide the output voltage down so it can
be compared with the LM1577-ADJ/LM2577-ADJ internal

1.23V reference. For a desired output voltage V

OUT

, select

R1 and R2 so that

4. Diode Selection

The switching diode in a flyback converter must withstand
the reverse voltage specified by the following equation.

A suitable diode must have a reverse voltage rating greater
than this. In addition it must be rated for more than the
average and peak diode currents listed in Figure 19.

5. Input Capacitor Selection

The primary of a flyback transformer draws discontinuous
pulses of current from the input supply. As a result, a flyback
regulator generates more noise at the input supply than a

www.national.com23

Application Hints (Continued)

step-up regulator, and this requires a larger bypass capacitor
to decouple the LM1577/LM2577 V
most applications, a low ESR, 1.0 µF cap will be sufficient, if
it is connected very close to the V

LM1577/LM2577

Transformer Input Dual Maximum

Type Voltage Output Output

L

= 100 µH 5V

P

1 N=1 5V

5V

10V

10V

2L

= 200 µH 10V

P

N = 0.5 12V

12V

12V

3L

= 250 µH 15V

P

N = 0.5 15V

15V

Transformer Manufacturers’ Part Numbers

Type AIE Pulse Renco

1 326-0637 PE-65300 RL-2580

2 330-0202 PE-65301 RL-2581

3 330-0203 PE-65302 RL-2582

pin from this noise. For

IN

and Ground pins.

IN

Voltage Current

±

10V 325 mA

±

12V 275 mA

±

15V 225 mA

±

10V 700 mA

±

12V 575 mA

±

15V 500 mA

±

10V 800 mA

±

12V 700 mA

±

15V 575 mA

±

10V 900 mA

±

12V 825 mA

±

15V 700 mA

ber consists of a fast recovery diode, and a parallel RC. The
RC values are selected for switch clamp voltage (V
that is 5V to 10V greater than V

. Use the following

SW(OFF)

CLAMP

equations to calculate R and C;

Power dissipation (and power rating) of the resistor is;

The fast recovery diode must have a reverse voltage rating
greater than V

CLAMP

.

)

FIGURE 20. Flyback Transformer Selection Guide

In addition to this bypass cap, a larger capacitor (≥ 47 µF)
should be used where the flyback transformer connects to
the input supply. This will attenuate noise which may inter­fere with other circuits connected to the same input supply
voltage.

6. Snubber Circuit

A “snubber” circuit is required when operating from input
voltages greater than 10V, or when using a transformer with

≥ 200 µH. This circuit clamps a voltage spike from the

L

P

transformer primary that occurs immediately after the output
switch turns off. Without it, the switch voltage may exceed
the 65V maximum rating. As shown in Figure 21, the snub-

01146819

FIGURE 21. Snubber Circuit

FLYBACK REGULATOR CIRCUIT EXAMPLE

±

The circuit of Figure 22 produces

15V (at 225 mA each)
from a single 5V input. The output regulation of this circuit is
shown in Figure 23 and Figure 25, while the load transient
response is shown in Figure 24 and Figure 26. Switching
waveforms seen in this circuit are shown in Figure 27.

www.national.com 24

Application Hints (Continued)

LM1577/LM2577

T1 = Pulse Engineering, PE-65300

D1, D2 = 1N5821

FIGURE 22. Flyback Regulator Easily Provides Dual Outputs

01146821

FIGURE 23. Line Regulation (Typical) of Flyback

Regulator of Figure 22, +15V Output

01146820

01146823

A: Output Voltage Change, 100 mV/div

B: Output Current, 100 mA/div

Horizontal: 10 ms/div

FIGURE 24. Load Transient Response of Flyback

Regulator of Figure 22, +15V Output

www.national.com25

Application Hints (Continued)

LM1577/LM2577

01146822

FIGURE 25. Line Regulation (Typical) of Flyback

Regulator of Figure 22, −15V Output

A: Switch pin voltage, 20 V/div

B: Primary current, 2 A/div

C: +15V Secondary current, 1 A/div

D: +15V Output ripple voltage, 100 mV/div

Horizontal: 5 µs/div

A: Output Voltage Change, 100 mV/div

01146824

B: Output Current, 100 mA/div

Horizontal: 10 ms/div

FIGURE 26. Load Transient Response of Flyback

Regulator of Figure 22, −15V Output

01146825

FIGURE 27. Switching Waveforms of Flyback Regulator of Figure 22, Each Output Loaded with 60Ω

www.national.com 26

Physical Dimensions inches (millimeters)

unless otherwise noted

LM1577/LM2577

TO-3 Metal Can Package (K)

Order Number LM1577K-12/883, LM1577K-15/883, or LM1577K-ADJ/883

NS Package Number K04A

0.300 Wide SO Package (M)

Order Number LM2577M-12, LM2577M-15 or LM2577M-ADJ

NS Package Number M24B

www.national.com27

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

LM1577/LM2577

Molded Dual-In-Line Package (N)

Order Number LM2577N-12, LM2577N-15, or LM2577N-ADJ

NS Package Number N16A

TO-220, Straight Leads (T)

Order Number LM2577T-12, LM2577T-15, or LM2577T-ADJ

NS Package Number TO5A

www.national.com 28

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

LM1577/LM2577

TO-220, Bent Staggered Leads (T)

Order Number LM2577T-12 Flow LB03, LM2577T-15 Flow LB03, or LM2577T-ADJ Flow LB03

NS Package Number T05D

www.national.com29

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

5-Lead TO-263 (S)

Order Number LM2577S-12, LM2577S-15 or LM2577S-ADJ

NS Package Number TS5B

LM1577/LM2577 SIMPLE SWITCHER Step-Up Voltage Regulator

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.

For the most current product information visit us at www.national.com.

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.

BANNED SUBSTANCE COMPLIANCE

National Semiconductor manufactures products and uses packing materials that 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

Email: [e-mail]
Tel: [phone]

National Semiconductor
Europe Customer Support Center

Fax: [phone]

Email: [e-mail]
Deutsch Tel: [phone]
English Tel: [phone]
Français Tel: [phone]

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.

National Semiconductor
Asia Pacific Customer
Support Center

Email: [e-mail]

National Semiconductor
Japan Customer Support Center

Fax: [phone]
Email: [e-mail]

LM1577/LM2577 SIMPLE SWITCHER Step-Up Voltage Regulator

Tel: [phone]www.national.com