LM1577/LM2577 SIMPLE SWITCHER Step-Up Voltage Regulator
April 2005
LM1577/LM2577
SIMPLE SWITCHER
®
Step-Up Voltage Regulator
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 regula-
tors.
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 compo-
nents, 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.
Features
Requires few external components
NPN output switches 3.0A, can stand off 65V
Wide input voltage range: 3.5V to 40V
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
n
n
n
n
Typical Applications
n
Simple boost regulator
n
Flyback and forward regulators
n
Multiple-output regulator
Connection Diagrams
Straight Leads
5-Lead TO-220 (T)
Bent, Staggered Leads
5-Lead TO-220 (T)
01146804
01146805
Top View
Order Number LM2577T-12, LM2577T-15,
or LM2577T-ADJ
See NS Package Number T05A
Top View
Order Number LM2577T-12 Flow LB03, LM2577T-15
Flow LB03, or LM2577T-ADJ Flow LB03
See NS Package Number T05D
SIMPLE SWITCHER
®
is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation
DS011468
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LM1577/LM2577
Connection Diagrams
(Continued)
24-Lead Surface Mount (M)
16-Lead DIP (N)
01146806
*No internal Connection
Top View
Order Number LM2577N-12, LM2577N-15,
or LM2577N-ADJ
See NS Package Number N16A
*No internal Connection
01146807
Top View
Order Number LM2577M-12, LM2577M-15,
or LM2577M-ADJ
See NS Package Number M24B
TO-263 (S)
5-Lead Surface-Mount Package
01146833
01146832
Top View
4-Lead TO-3 (K)
Side View
Order Number LM2577S-12, LM2577S-15,
or LM2577S-ADJ
See NS Package Number TS5B
01146808
Bottom View
Order Number LM1577K-12/883, LM1577K-15/883,
or LM1577K-ADJ/883
See NS Package Number K04A
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2
LM1577/LM2577
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
Output Switch Voltage
Output Switch Current (Note 2)
Power Dissipation
Storage Temperature Range
Lead Temperature
(Soldering, 10 sec.)
Maximum Junction Temperature
260˚C
150˚C
45V
65V
6.0A
Internally Limited
−65˚C to +150˚C
Minimum ESD Rating
(C = 100 pF, R = 1.5 kΩ)
2 kV
Operating Ratings
Supply Voltage
Output Switch Voltage
Output Switch Current
Junction Temperature Range
LM1577
LM2577
−55˚C
≤
T
J
≤
+150˚C
−40˚C
≤
T
J
≤
+125˚C
3.5V
≤
V
IN
≤
40V
0V
≤
V
SWITCH
≤
60V
I
SWITCH
≤
3.0A
Electrical Characteristics—LM1577-12, LM2577-12
Specifications with standard type face are for T
J
= 25˚C, and those in
bold type face
apply over full
Operating Temperature
Range.
Unless otherwise specified, V
IN
= 5V, and I
SWITCH
= 0.
LM1577-12
Symbol
Parameter
Conditions
Typical
Limit
(Notes 3, 4)
SYSTEM PARAMETERS
Circuit of
Figure 1
(Note 6)
V
OUT
Output Voltage
V
IN
= 5V to 10V
I
LOAD
= 100 mA to 800 mA
(Note 3)
Line Regulation
V
IN
= 3.5V to 10V
I
LOAD
= 300 mA
Load Regulation
V
IN
= 5V
I
LOAD
= 100 mA to 800 mA
η
I
S
Efficiency
Input Supply Current
V
IN
= 5V, I
LOAD
= 800 mA
V
FEEDBACK
= 14V (Switch Off)
I
SWITCH
= 2.0A
V
COMP
= 2.0V (Max Duty Cycle)
V
UV
Input Supply
Undervoltage Lockout
f
O
Oscillator Frequency
Measured at Switch Pin
I
SWITCH
= 100 mA
V
REF
Output Reference
Voltage
Output Reference
Voltage Line Regulator
R
FB
G
M
Feedback Pin Input
Resistance
Error Amp
Transconductance
I
COMP
= −30 µA to +30 µA
V
COMP
= 1.0V
370
225/145
515/615
225/145
515/615
µmho
µmho(min)
µmho(max)
9.7
kΩ
Measured at Feedback Pin
V
IN
= 3.5V to 40V
V
COMP
= 1.0V
V
IN
= 3.5V to 40V
7
12
11.76/11.64
12.24/12.36
11.76/11.64
12.24/12.36
52
48/42
56/62
48/42
56/62
I
SWITCH
= 100 mA
2.90
2.70/2.65
3.10/3.15
2.70/2.65
3.10/3.15
80
7.5
10.0/14.0
25
50/85
50/85
10.0/14.0
DEVICE PARAMETERS
mA
mA(max)
mA
mA(max)
V
V(min)
V(max)
kHz
kHz(min)
kHz(max)
V
V(min)
V(max)
mV
20
50/100
50/100
20
50/100
50/100
12.0
11.60/11.40
12.40/12.60
11.60/11.40
12.40/12.60
V
V(min)
V(max)
mV
mV(max)
mV
mV(max)
%
LM2577-12
Limit
(Note 5)
Units
(Limits)
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4
LM1577/LM2577
Electrical Characteristics—LM1577-12, LM2577-12
(Continued)
Specifications with standard type face are for T
J
= 25˚C, and those in
bold type face
apply over full
Operating Temperature
Range.
Unless otherwise specified, V
IN
= 5V, and I
SWITCH
= 0.
LM1577-12
Symbol
Parameter
Conditions
Typical
Limit
(Notes 3, 4)
LM2577-12
Limit
(Note 5)
V/V
50/25
2.4
2.2/2.0
0.3
0.40/0.55
0.40/0.55
2.2/2.0
50/25
V/V(min)
V
V(min)
V
V(max)
µA
µA(min)
µA(max)
µA
2.5/1.5
7.5/9.5
95
93/90
12.5
93/90
2.5/1.5
7.5/9.5
µA(min)
µA(max)
%
%(min)
A/V
Units
(Limits)
DEVICE PARAMETERS
A
VOL
Error Amp
Voltage Gain
Error Amplifier
Output Swing
V
COMP
= 1.1V to 1.9V
R
COMP
= 1.0 MΩ
(Note 7)
Upper Limit
V
FEEDBACK
= 10.0V
Lower Limit
V
FEEDBACK
= 15.0V
Error Amplifier
Output Current
I
SS
Soft Start Current
V
FEEDBACK
= 10.0V to 15.0V
V
COMP
= 1.0V
V
FEEDBACK
= 10.0V
V
COMP
= 0V
D
Maximum Duty Cycle
Switch
Transconductance
I
L
V
SAT
Switch Leakage
Current
Switch Saturation
Voltage
NPN Switch
Current Limit
V
SWITCH
= 65V
V
FEEDBACK
= 15V (Switch Off)
I
SWITCH
= 2.0A
V
COMP
= 2.0V (Max Duty Cycle)
4.5
3.7/3.0
5.3/6.0
3.7/3.0
5.3/6.0
0.5
0.7/0.9
0.7/0.9
V
COMP
= 1.5V
I
SWITCH
= 100 mA
5.0
80
±
200
±
130/
±
90
±
300/
±
400
±
130/
±
90
±
300/
±
400
10
300/600
300/600
µA
µA(max)
V
V(max)
A
A(min)
A(max)
Electrical Characteristics—LM1577-15, LM2577-15
Specifications with standard type face are for T
J
= 25˚C, and those in
bold type face
apply over full
Operating Temperature
Range.
Unless otherwise specified, V
IN
= 5V, and I
SWITCH
= 0.
LM1577-15
Symbol
Parameter
Conditions
Typical
Limit
(Notes 3, 4)
SYSTEM PARAMETERS
Circuit of
Figure 2
(Note 6)
V
OUT
Output Voltage
V
IN
= 5V to 12V
I
LOAD
= 100 mA to 600 mA
(Note 3)
Line Regulation
V
IN
= 3.5V to 12V
I
LOAD
= 300 mA
Load Regulation
V
IN
= 5V
I
LOAD
= 100 mA to 600 mA
η
Efficiency
V
IN
= 5V, I
LOAD
= 600 mA
80
20
50/100
50/100
20
50/100
50/100
15.0
14.50/14.25
15.50/15.75
14.50/14.25
15.50/15.75
V
V(min)
V(max)
mV
mV(max)
mV
mV(max)
%
LM2577-15
Limit
(Note 5)
Units
(Limits)
5
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