LM1577/LM2577 Series
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 ver-
sions: 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 3.0ANPN 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
nRequires few external components
nNPN output switches 3.0A, can stand off 65V
nWide input voltage range: 3.5V to 40V
nCurrent-mode operation for improved transient
response, line regulation, and current limit
n52 kHz internal oscillator
nSoft-start function reduces in-rush current during start-up
nOutput switch protected by current limit, under-voltage
lockout, and thermal shutdown
Typical Applications
nSimple boost regulator
nFlyback and forward regulators
nMultiple-output regulator
Typical Application
Ordering Information
Temperature
Range Package
Type Output Voltage NSC
12V 15V ADJ Package Package
Drawing
−40˚C T
A
+125˚C 24-Pin Surface Mount LM2577M-12 LM2577M-15 LM2577M-ADJ M24B SO
16-Pin Molded DIP LM2577N-12 LM2577N-15 LM2577N-ADJ N16A N
5-Lead Surface Mount LM2577S-12 LM2577S-15 LM2577S-ADJ TS5B TO-263
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
A
+150˚C 4-Pin TO-3 LM1577K-12/883 LM1577K-15/883 LM1577K-
ADJ/883 K04A TO-3
SIMPLE SWITCHER®is a registered trademark of National Semiconductor Corporation.
DS011468-1
Note: Pin numbers shown are for TO-220 (T) package.
June 1999
LM1577/LM2577 Series SIMPLE SWITCHER Step-Up Voltage Regulator
© 1999 National Semiconductor Corporation DS011468 www.national.com
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 45V
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
Maximum Junction Temperature 150˚C
Minimum ESD Rating
(C =100 pF, R =1.5 k)2kV
Operating Ratings
Supply Voltage 3.5V V
IN
40V
Output Switch Voltage 0V V
SWITCH
60V
Output Switch Current I
SWITCH
3.0A
Junction Temperature Range
LM1577 −55˚C T
J
+150˚C
LM2577 −40˚C T
J
+125˚C
Electrical CharacteristicsLM1577-12, 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 LM2577-12 Units
Symbol Parameter Conditions Typical Limit Limit (Limits)
(Notes 3, 4) (Note 5)
SYSTEM PARAMETERS Circuit of
Figure 1
(Note 6)
V
OUT
Output Voltage V
IN
=5V to 10V 12.0 V
I
LOAD
=100 mA to 800 mA 11.60/11.40 11.60/11.40 V(min)
(Note 3) 12.40/12.60 12.40/12.60 V(max)
Line Regulation V
IN
=3.5V to 10V 20 mV
I
LOAD
=300 mA 50/100 50/100 mV(max)
Load Regulation V
IN
=5V 20 mV
I
LOAD
=100 mA to 800 mA 50/100 50/100 mV(max)
ηEfficiency V
IN
=5V, I
LOAD
=800 mA 80 %
DEVICE PARAMETERS
I
S
Input Supply Current V
FEEDBACK
=14V (Switch Off) 7.5 mA
10.0/14.0 10.0/14.0 mA(max)
I
SWITCH
=2.0A 25 mA
V
COMP
=2.0V (Max Duty Cycle) 50/85 50/85 mA(max)
V
UV
Input Supply I
SWITCH
=100 mA 2.90 V
Undervoltage Lockout 2.70/2.65 2.70/2.65 V(min)
3.10/3.15 3.10/3.15 V(max)
f
O
Oscillator Frequency Measured at Switch Pin 52 kHz
I
SWITCH
=100 mA 48/42 48/42 kHz(min)
56/62 56/62 kHz(max)
V
REF
Output Reference Measured at Feedback Pin V
Voltage V
IN
=3.5V to 40V 12 11.76/11.64 11.76/11.64 V(min)
V
COMP
=1.0V 12.24/12.36 12.24/12.36 V(max)
Output Reference V
IN
=3.5V to 40V 7mV
Voltage Line Regulator
R
FB
Feedback Pin Input 9.7 k
Resistance
G
M
Error Amp I
COMP
=−30 µA to +30 µA 370 µmho
Transconductance V
COMP
=1.0V 225/145 225/145 µmho(min)
515/615 515/615 µmho(max)
A
VOL
Error Amp V
COMP
=1.1V to 1.9V 80 V/V
Voltage Gain R
COMP
=1.0 M50/25 50/25 V/V(min)
(Note 7)
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Electrical CharacteristicsLM1577-12, 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 LM2577-12 Units
Symbol Parameter Conditions Typical Limit Limit (Limits)
(Notes 3, 4) (Note 5)
DEVICE PARAMETERS
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
V
FEEDBACK
=15.0V 0.40/0.55 0.40/0.55 V(max)
Error Amplifier V
FEEDBACK
=10.0V to 15.0V ±200 µA
Output Current V
COMP
=1.0V ±130/±90 ±130/±90 µA(min)
±300/±400 ±300/±400 µA(max)
I
SS
Soft Start Current V
FEEDBACK
=10.0V 5.0 µA
V
COMP
=0V 2.5/1.5 2.5/1.5 µA(min)
7.5/9.5 7.5/9.5 µA(max)
D Maximum Duty Cycle V
COMP
=1.5V 95 %
I
SWITCH
=100 mA 93/90 93/90 %(min)
Switch
Transconductance 12.5 A/V
I
L
Switch Leakage V
SWITCH
=65V 10 µA
Current V
FEEDBACK
=15V (Switch Off) 300/600 300/600 µA(max)
V
SAT
Switch Saturation I
SWITCH
=2.0A 0.5 V
Voltage V
COMP
=2.0V (Max Duty Cycle) 0.7/0.9 0.7/0.9 V(max)
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 CharacteristicsLM1577-15, 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 LM2577-15 Units
Symbol Parameter Conditions Typical Limit Limit (Limits)
(Notes 3, 4) (Note 5)
SYSTEM PARAMETERS Circuit of
Figure 2
(Note 6)
V
OUT
Output Voltage V
IN
=5V to 12V 15.0 V
I
LOAD
=100 mA to 600 mA 14.50/14.25 14.50/14.25 V(min)
(Note 3) 15.50/15.75 15.50/15.75 V(max)
Line Regulation V
IN
=3.5V to 12V 20 50/100 50/100 mV
I
LOAD
=300 mA mV(max)
Load Regulation V
IN
=5V 20 50/100 50/100 mV
I
LOAD
=100 mA to 600 mA mV(max)
ηEfficiency V
IN
=5V, I
LOAD
=600 mA 80 %
DEVICE PARAMETERS
I
S
Input Supply Current V
FEEDBACK
=18.0V 7.5 mA
(Switch Off) 10.0/14.0 10.0/14.0 mA(max)
I
SWITCH
=2.0A 25 mA
V
COMP
=2.0V 50/85 50/85 mA(max)
(Max Duty Cycle)
V
UV
Input Supply I
SWITCH
=100 mA 2.90 V
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Electrical CharacteristicsLM1577-15, LM2577-15 (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.
LM1577-15 LM2577-15 Units
Symbol Parameter Conditions Typical Limit Limit (Limits)
(Notes 3, 4) (Note 5)
DEVICE PARAMETERS
Undervoltage 2.70/2.65 2.70/2.65 V(min)
Lockout 3.10/3.15 3.10/3.15 V(max)
f
O
Oscillator Frequency Measured at Switch Pin 52 kHz
I
SWITCH
=100 mA 48/42 48/42 kHz(min)
56/62 56/62 kHz(max)
V
REF
Output Reference Measured at Feedback Pin V
Voltage V
IN
=3.5V to 40V 15 14.70/14.55 14.70/14.55 V(min)
V
COMP
=1.0V 15.30/15.45 15.30/15.45 V(max)
Output Reference V
IN
=3.5V to 40V 10 mV
Voltage Line Regulation
R
FB
Feedback Pin Input 12.2 k
Voltage Line Regulator
G
M
Error Amp I
COMP
=−30 µA to +30 µA 300 µmho
Transconductance V
COMP
=1.0V 170/110 170/110 µmho(min)
420/500 420/500 µmho(max)
A
VOL
Error Amp V
COMP
=1.1V to 1.9V 65 V/V
Voltage Gain R
COMP
=1.0 M40/20 40/20 V/V(min)
(Note 7)
Error Amplifier Upper Limit 2.4 V
Output Swing V
FEEDBACK
=12.0V 2.2/2.0 2.2/2.0 V(min)
Lower Limit 0.3 V
V
FEEDBACK
=18.0V 0.4/0.55 0.40/0.55 V(max)
Error Amp V
FEEDBACK
=12.0V to 18.0V ±200 µA
Output Current V
COMP
=1.0V ±130/±90 ±130/±90 µA(min)
±300/±400 ±300/±400 µA(max)
I
SS
Soft Start Current V
FEEDBACK
=12.0V 5.0 µA
V
COMP
=0V 2.5/1.5 2.5/1.5 µA(min)
7.5/9.5 7.5/9.5 µA(max)
D Maximum Duty V
COMP
=1.5V 95 %
Cycle I
SWITCH
=100 mA 93/90 93/90 %(min)
Switch
Transconductance 12.5 A/V
I
L
Switch Leakage V
SWITCH
=65V 10 µA
Current V
FEEDBACK
=18.0V 300/600 300/600 µA(max)
(Switch Off)
V
SAT
Switch Saturation I
SWITCH
=2.0A 0.5 V
Voltage V
COMP
=2.0V 0.7/0.9 0.7/0.9 V(max)
(Max Duty Cycle)
NPN Switch V
COMP
=2.0V 4.3 A
Current Limit 3.7/3.0 3.7/3.0 A(min)
5.3/6.0 5.3/6.0 A(max)
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Electrical CharacteristicsLM1577-ADJ, LM2577-ADJ
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, V
FEEDBACK
=V
REF
, and I
SWITCH
=0.
LM1577-ADJ LM2577-ADJ Units
Symbol Parameter Conditions Typical Limit Limit (Limits)
(Notes 3, 4) (Note 5)
SYSTEM PARAMETERS Circuit of
Figure 3
(Note 6)
V
OUT
Output Voltage V
IN
=5V to 10V 12.0 V
I
LOAD
=100 mA to 800 mA 11.60/11.40 11.60/11.40 V(min)
(Note 3) 12.40/12.60 12.40/12.60 V(max)
V
OUT
/ Line Regulation V
IN
=3.5V to 10V 20 mV
V
IN
I
LOAD
=300 mA 50/100 50/100 mV(max)
V
OUT
/ Load Regulation V
IN
=5V 20 mV
I
LOAD
I
LOAD
=100 mA to 800 mA 50/100 50/100 mV(max)
ηEfficiency V
IN
=5V, I
LOAD
=800 mA 80 %
DEVICE PARAMETERS
I
S
Input Supply Current V
FEEDBACK
=1.5V (Switch Off) 7.5 mA
10.0/14.0 10.0/14.0 mA(max)
I
SWITCH
=2.0A 25 mA
V
COMP
=2.0V (Max Duty Cycle) 50/85 50/85 mA(max)
V
UV
Input Supply I
SWITCH
=100 mA 2.90 V
Undervoltage Lockout 2.70/2.65 2.70/2.65 V(min)
3.10/3.15 3.10/3.15 V(max)
f
O
Oscillator Frequency Measured at Switch Pin 52 kHz
I
SWITCH
=100 mA 48/42 48/42 kHz(min)
56/62 56/62 kHz(max)
V
REF
Reference Measured at Feedback Pin V
Voltage V
IN
=3.5V to 40V 1.230 1.214/1.206 1.214/1.206 V(min)
V
COMP
=1.0V 1.246/1.254 1.246/1.254 V(max)
V
REF
/ Reference Voltage V
IN
=3.5V to 40V 0.5 mV
V
IN
Line Regulation
I
B
Error Amp V
COMP
=1.0V 100 nA
Input Bias Current 300/800 300/800 nA(max)
G
M
Error Amp I
COMP
=−30 µA to +30 µA 3700 µmho
Transconductance V
COMP
=1.0V 2400/1600 2400/1600 µmho(min)
4800/5800 4800/5800 µmho(max)
A
VOL
Error Amp V
COMP
=1.1V to 1.9V 800 V/V
Voltage Gain R
COMP
=1.0 M(Note 7) 500/250 500/250 V/V(min)
Error Amplifier Upper Limit 2.4 V
Output Swing V
FEEDBACK
=1.0V 2.2/2.0 2.2/2.0 V(min)
Lower Limit 0.3 V
V
FEEDBACK
=1.5V 0.40/0.55 0.40/0.55 V(max)
Error Amp V
FEEDBACK
=1.0V to 1.5V ±200 µA
Output Current V
COMP
=1.0V ±130/±90 ±130/±90 µA(min)
±300/±400 ±300/±400 µA(max)
I
SS
Soft Start Current V
FEEDBACK
=1.0V 5.0 µA
V
COMP
=0V 2.5/1.5 2.5/1.5 µA(min)
7.5/9.5 7.5/9.5 µA(max)
D Maximum Duty Cycle V
COMP
=1.5V 95 %
I
SWITCH
=100 mA 93/90 93/90 %(min)
I
SWITCH
/ Switch 12.5 A/V
V
COMP
Transconductance
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Electrical CharacteristicsLM1577-ADJ, LM2577-ADJ (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, V
FEEDBACK
=V
REF
, and I
SWITCH
=0.
LM1577-ADJ LM2577-ADJ Units
Symbol Parameter Conditions Typical Limit Limit (Limits)
(Notes 3, 4) (Note 5)
DEVICE PARAMETERS
I
L
Switch Leakage V
SWITCH
=65V 10 µA
Current V
FEEDBACK
=1.5V (Switch Off) 300/600 300/600 µA(max)
V
SAT
Switch Saturation I
SWITCH
=2.0A 0.5 V
Voltage V
COMP
=2.0V (Max Duty Cycle) 0.7/0.9 0.7/0.9 V(max)
NPN Switch V
COMP
=2.0V 4.3 A
Current Limit 3.7/3.0 3.7/3.0 A(min)
5.3/6.0 5.3/6.0 A(max)
THERMAL PARAMETERS (All Versions)
θ
JA
Thermal Resistance K Package, Junction to Ambient 35
˚C/W
θ
JC
K Package, Junction to Case 1.5
θ
JA
T Package, Junction to Ambient 65
θ
JC
T Package, Junction to Case 2
θ
JA
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: Amilitary 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%produc-
tion 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 Mresistor is connected to the compensation pin (which is the error amplifier’s output) to ensure accuracy in measuring AVOL. In actual applications,
this pin’s load resistance should be 10 M, resulting in AVOL that is typically twice the guaranteed minimum limit.
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, θJA is 50˚C/W; with 1 square inch of copper area, θJA is 37˚C/W; and with 1.6 or more square inches of copper area, θJA is 32˚C/W.
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Typical Performance Characteristics
Reference Voltage
vs Temperature
DS011468-34
Reference Voltage
vs Temperature
DS011468-35
Reference Voltage
vs Temperature
DS011468-36
Reference Voltage
vs Supply Voltage
DS011468-37
Reference Voltage
vs Supply Voltage
DS011468-38
Reference Voltage
vs Supply Voltage
DS011468-39
Error Amp Transconductance
vs Temperature
DS011468-40
Error Amp Transconductance
vs Temperature
DS011468-41
Error Amp Transconductance
vs Temperature
DS011468-42
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Typical Performance Characteristics (Continued)
Error Amp Voltage
Gain vs Temperature
DS011468-43
Error Amp Voltage
Gain vs Temperature
DS011468-44
Error Amp Voltage
Gain vs Temperature
DS011468-45
Quiescent Current
vs Temperature
DS011468-46
Quiescent Current
vs Switch Current
DS011468-47
Current Limit
vs Temperature
DS011468-48
Current Limit Response
Time vs Overdrive
DS011468-49
Switch Saturation Voltage
vs Switch Current
DS011468-50
Switch Transconductance
vs Temperature
DS011468-51
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Typical Performance Characteristics (Continued)
Connection Diagrams
Feedback Pin Bias
Current vs Temperature
DS011468-52
Oscillator Frequency
vs Temperature
DS011468-53
Maximum Power Dissipation
(TO-263) (Note 9)
DS011468-31
Straight Leads
5-Lead TO-220 (T)
DS011468-4
Top View
Order Number LM2577T-12, LM2577T-15,
or LM2577T-ADJ
See NS Package Number T05A
Bent, Staggered Leads
5-Lead TO-220 (T)
DS011468-5
Top View
Order Number LM2577T-12 Flow LB03, LM2577T-15
Flow LB03, or LM2577T-ADJ Flow LB03
See NS Package Number T05D
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Connection Diagrams (Continued)
16-Lead DIP (N)
DS011468-6
*No internal Connection
Top View
Order Number LM2577N-12, LM2577N-15,
or LM2577N-ADJ
See NS Package Number N16A
24-Lead Surface Mount (M)
DS011468-7
*No internal Connection
Top View
Order Number LM2577M-12, LM2577M-15,
or LM2577M-ADJ
See NS Package Number M24B
TO-263 (S)
5-Lead Surface-Mount Package
DS011468-32
Top View
DS011468-33
Side View
Order Number LM2577S-12, LM2577S-15,
or LM2577S-ADJ
See NS Package Number TS5B
4-Lead TO-3 (K)
DS011468-8
Bottom View
Order Number LM1577K-12/883, LM1577K-15/883,
or LM1577K-ADJ/883
See NS Package Number K04A
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LM1577-12, LM2577-12 Test Circuit
LM1577-15, LM2577-15 Test Circuit
LM1577-ADJ, LM2577-ADJ Test Circuit
DS011468-30
L=415-0930 (AIE)
D=any manufacturer
COUT =Sprague Type 673D
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
DS011468-26
L=415-0930 (AIE)
D=any manufacturer
COUT =Sprague Type 673D
Electrolytic 680 µF, 20V
Note: Pin numbers shown are for TO-220 (T) package
FIGURE 2. Circuit Used to Specify System Parameters for 15V Versions
DS011468-9
L=415-0930 (AIE)
D=any manufacturer
COUT =Sprague Type 673D
Electrolytic 680 µF, 20V
R1 =48.7k in series with 511(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
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Application Hints
DS011468-10
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
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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 di-
rectly 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 fre-
quency 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
IN
/L, storing current in the inductor. When the
switch turns off, the lower end of the inductor flies above V
IN
,
discharging its current through diode (D) into the output ca-
pacitor (C
OUT
) at a rate of (V
OUT
−V
IN
)/L. Thus, 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 feed-
back 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 cur-
rent 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
Fig-
ure 6
.
STEP-UP REGULATOR DESIGN PROCEDURE
The following design procedure can be used to select the ap-
propriate external components for the circuit in
Figure 4
,
based on these system requirements.
Given:
V
IN (min)
=Minimum input supply voltage
V
OUT
=Regulated output voltage
I
LOAD(max)
=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 V
IN
. The upper
limits for V
OUT
and I
LOAD(max)
are given by the following
equations.
V
OUT
60V
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
DS011468-11
FIGURE 5. Step-Up Regulator Waveforms
Duty Cycle D
Average
Inductor
Current I
IND(AVE)
Inductor
Current
Ripple I
IND
Peak
Inductor
Current I
IND(PK)
Peak Switch
Current I
SW(PK)
Switch
Voltage
When Off V
SW(OFF)
V
OUT
+V
F
Diode
Reverse
Voltage V
R
V
OUT
−V
SAT
Average
Diode
Current I
D(AVE)
I
LOAD
Peak Diode
Current I
D(PK)
Power
Dissipation
of
LM1577/2577
P
D
VF=Forward Biased Diode Voltage
ILOAD =Output Load Current
FIGURE 6. Step-Up Regulator Formulas
www.national.com13
Application Hints (Continued)
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
conditions 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.
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:
D
(max)
, the maximum switch duty cycle (0 D0.9):
where V
F
=0.5V for Schottky diodes and 0.8V for fast recov-
ery diodes (typically);
E
T
, the product of volts x time that charges the inductor:
I
IND,DC
, the average inductor current under full load;
B.
Identify Inductor Value:
1. From
Figure 9
, identify the inductor code for the re-
gion indicated by the intersection of ET 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 ETof90V
µs (L) or 250 Vµs (H).
2. If D <0.85, go on to step C. If D 0.85, then calcu-
late the minimum inductance needed to ensure the
switching regulator’s stability:
If L
MIN
is smaller than the inductor value found in step B1, go
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:
1. Find the lowest value inductor that is greater than L
MIN
.
2. Find where ET intersects this inductor value to determine
if it has an L or H prefix. If ET intersects both the L and H re-
gions, select the inductor with an H prefix.
DS011468-27
FIGURE 7. LM2577-12 Inductor Selection Guide
DS011468-28
FIGURE 8. LM2577-15 Inductor Selection Guide
www.national.com 14
Application Hints (Continued)
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 specifica-
tions for these inductors are available from the respec-
tive 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 ET and peak current, as this
will saturate the core.
Pulse:
powdered iron, toroid core inductors; Benefits are
low EMI and ability to withstand ET and peak current
above rated value better than ferrite cores.
Renco:
ferrite, bobbin-core inductors; Benefits are low
cost and best ability to withstand ET and peak current
above rated value. Be aware that these inductors gener-
ate more EMI than the other types, and this may inter-
fere with signals sensitive to noise.
DS011468-12
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.
FIGURE 9. LM1577-ADJ/LM2577-ADJ Inductor Selection Graph
www.national.com15
Application Hints (Continued)
2. Compensation Network (R
C
,C
C
) and Output Capacitor
(C
OUT
) Selection
R
C
and C
C
form a pole-zero compensation network that sta-
bilizes the regulator. The values of R
C
and C
C
are mainly de-
pendant on the regulator voltage gain, I
LOAD(max)
, L and
C
OUT
. The following procedure calculates values for R
C
,C
C
,
and C
OUT
that ensure regulator stability. Be aware that this
procedure doesn’t necessarily result in R
C
and C
C
that pro-
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
OUT
tran-
sient response when pulsing I
LOAD
(see
Figure 15
).
A.
First, calculate the maximum value for R
C
.
Select a resistor less than or equal to this value, and it
should also be no greater than 3 k.
B.
Calculate the minimum value for
C
OUT
using the following
two equations.
The larger of these two values is the minimum value that en-
sures stability.
C.
Calculate the minimum value of C
C
.
The compensation capacitor is also part of the soft start cir-
cuitry. When power to the regulator is turned on, the switch
duty cycle is allowed to rise at a rate controlled by this ca-
pacitor (with no control on the duty cycle, it would immedi-
ately rise to 90%, drawing huge currents from the input
power supply). In order to operate properly, the soft start cir-
cuit requires C
C
0.22 µF.
The value of the output filter capacitor is normally large
enough to require the use of aluminum electrolytic capaci-
tors.
Figure 11
lists several different types that are recom-
mended for switching regulators, and the following param-
eters are used to select the proper capacitor.
Working Voltage (WVDC):
Choose a capacitor with a work-
ing voltage at least 20%higher than the regulator output volt-
age.
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
of R
C
and C
C
needed to stabilize the regulator. As a result,
the preceding calculations for C
C
and R
C
are only valid if
ESR doesn’t exceed the maximum value specified by the fol-
lowing equations.
Select a capacitor with ESR, at 52 kHz, that is less than or
equal to the lower value calculated. Most electrolytic capaci-
tors 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.
Inductor Manufacturer’s Part Number
Code Schott Pulse Renco
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., (612) 475-1173
1000 Parkers Lake Rd., Wayzata, MN 55391
Pulse Engineering, (619) 268-2400
P.O. Box 12235, San Diego, CA 92112
Renco Electronics Inc., (516) 586-5566
60 Jeffryn Blvd. East, Deer Park, NY 11729
FIGURE 10. Table of Standardized Inductors and
Manufacturer’s Part Numbers
www.national.com 16
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 V
OUT
=1.23V (1 + R1/R2)
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
OUT
,
select R1 and R2 so that
4. Input Capacitor Selection (C
IN
)
The switching action in the step-up regulator causes a trian-
gular 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.
If the LM1577 is located far from the supply source filter ca-
pacitors, 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 with-
stand 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
LOAD(max)
and I
D(PK)
. Schottky barrier diodes are often favored for use
in switching regulators. Their low forward voltage drop allows
higher regulator efficiency than if a (less expensive) fast re-
covery diode was used. See
Figure 12
for recommended
part numbers and voltage ratings of 1A and 3A diodes.
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
Fig-
ure 15
. The switching waveforms observed during the opera-
tion of this circuit are shown in
Figure 16
.
Cornell Dublier Types 239, 250, 251, UFT,
300, or 350
P.O. Box 128, Pickens, SC 29671
(803) 878-6311
Nichicon Types PF, PX, or PZ
927 East Parkway,
Schaumburg, IL 60173
(708) 843-7500
Sprague Types 672D, 673D, or 674D
Box 1, Sprague Road,
Lansing, NC 28643
(919) 384-2551
United Chemi-Con Types LX, SXF, or SXJ
9801 West Higgins Road,
Rosemont, IL 60018
(708) 696-2000
FIGURE 11. Aluminum Electrolytic Capacitors
Recommended for Switching Regulators
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
www.national.com17
Application Hints (Continued)
DS011468-13
Note: Pin numbers shown are for TO-220 (T) package.
FIGURE 13. Step-up Regulator Delivers 12V from a 5V Input
DS011468-14
FIGURE 14. Line Regulation (Typical) of Step-Up Regulator of
Figure 13
DS011468-15
A: Output Voltage Change, 100 mV/div. (AC-coupled)
B: Load current, 0.2 A/div
Horizontal: 5 ms/div
FIGURE 15. Load Transient Response of Step-Up
Regulator of
Figure 13
DS011468-16
A: Switch pin voltage, 10 V/div
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
www.national.com 18
Application Hints (Continued)
FLYBACK REGULATOR
A Flyback regulator can produce single or multiple output
voltages that are lower or greater than the input supply volt-
age.
Figure 18
shows the LM1577/LM2577 used as a fly-
back regulator with positive and negative regulated outputs.
Its operation is similar to a step-up regulator, except the out-
put switch contols the primary current of a flyback trans-
former. 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 out-
puts. 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
Fig-
ure 19
.
FLYBACK REGULATOR DESIGN PROCEDURE
1. Transformer Selection
A family of standardized flyback transformers is available for
creating flyback regulators that produce dual output volt-
ages, from ±10V to ±15V, as shown in
Figure 18
.
Figure
20
lists these transformers with the input voltage, output volt-
ages and maximum load current they are designed for.
2. Compensation Network (C
C
,R
C
) and
Output Capacitor (C
OUT
) Selection
As explained in the Step-Up Regulator Design Procedure,
C
C
,R
C
and C
OUT
must be selected as a group. The following
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.
A. First, calculate the maximum value for R
C
.
Where I
LOAD(max)
is the sum of the load current (magni-
tude) required from both outputs. Select a resistor less than
or equal to this value, and no greater than 3 k.
B. Calculate the minimum value for C
OUT
(sum of C
OUT
at both outputs) using the following two equations.
The larger of these two values must be used to ensure regu-
lator stability.
DS011468-17
FIGURE 17. Flyback Regulator Waveforms
DS011468-18
T1 =Pulse Engineering, PE-65300
D1, D2 =1N5821
FIGURE 18. LM1577-ADJ/LM2577-ADJ Flyback Regulator with ±Outputs
www.national.com19
Application Hints (Continued)
C.
Calculate the minimum value of C
C
D.
Calculate the maximum ESR
of the +V
OUT
and −V
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 Regu-
lator 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 V
OUT
=1.23V (1 + R1/R2)
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 aver-
age 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
step-up regulator, and this requires a larger bypass capacitor
to decouple the LM1577/LM2577 V
IN
pin from this noise. For
most applications, a low ESR, 1.0 µF cap will be sufficient, if
it is connected very close to the V
IN
and Ground pins.
Duty Cycle D
Primary Current Variation I
P
Peak Primary Current I
P(PK)
Switch Voltage when Off V
SW(OFF)
Diode Reverse Voltage V
R
V
OUT+
N(V
IN
V
SAT
)
Average Diode Current I
D(AVE)
I
LOAD
Peak Diode Current I
D(PK)
Short Circuit Diode Current
Power Dissipation of
LM1577/LM2577
P
D
DS011468-78
FIGURE 19. Flyback Regulator Formulas
www.national.com 20
Application Hints (Continued)
Transformer Input Dual Maxi-
mum
Type Voltage Output Output
Voltage Current
L
P
=100 µH 5V ±10V 325 mA
1N
=
15V
±
12V 275 mA
5V ±15V 225 mA
10V ±10V 700 mA
10V ±12V 575 mA
2L
P
=
200 µH 10V ±15V 500 mA
N=0.5 12V ±10V 800 mA
12V ±12V 700 mA
12V ±15V 575 mA
3L
P
=
250 µH 15V ±10V 900 mA
N=0.5 15V ±12V 825 mA
15V ±15V 700 mA
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 inter-
fere 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
L
P
200 µH. This circuit clamps a voltage spike from the
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-
ber consists of a fast recovery diode, and a parallel RC. The
RC values are selected for switch clamp voltage (V
CLAMP
)
that is 5V to 10V greater than V
SW(OFF)
. Use the following
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
.
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
.
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
FIGURE 20. Flyback Transformer Selection Guide
DS011468-19
FIGURE 21. Snubber Circuit
www.national.com21
Application Hints (Continued)
DS011468-20
T1 =Pulse Engineering, PE-65300
D1, D2 =1N5821
FIGURE 22. Flyback Regulator Easily Provides Dual Outputs
DS011468-21
FIGURE 23. Line Regulation (Typical) of Flyback
Regulator of
Figure 22
, +15V Output
DS011468-23
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
DS011468-22
FIGURE 25. Line Regulation (Typical) of Flyback
Regulator of
Figure 22
, −15V Output
DS011468-24
A: Output Voltage Change, 100 mV/div
B: Output Current, 100 mA/div
Horizontal: 10 ms/div
FIGURE 26. Load Transient Response of Flyback
Regulator of
Figure 22
, −15V Output
www.national.com 22
Application Hints (Continued)
DS011468-25
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
FIGURE 27. Switching Waveforms of Flyback Regulator of
Figure 22
, Each Output Loaded with 60
www.national.com23
Physical Dimensions inches (millimeters) unless otherwise noted
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.com 24
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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.com25
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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.com 26
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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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.
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www.national.com
5-Lead TO-263 (S)
Order Number LM2577S-12, LM2577S-15 or LM2577S-ADJ
NS Package Number TS5B
LM1577/LM2577 Series 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.
National P/N LM1577 - SIMPLE SWITCHER Step-Up Voltage Regulator
See Wireless Products
Products > Analog - Regulators > Simple Switchers > LM1577
LM1577 Product Folder
SIMPLE SWITCHER Step-Up Voltage Regulator
Generic P/N 1577
General
Description Features Datasheet Package
& Models Samples
& Pricing Design
Tools
Parametric Table Parametric Table
Multiple Output Capability Yes
On/Off Pin No
Error Flag No
Input Voltage, min (Volt) 3.50
Input Voltage, max (Volt) 40
Output Current, max 3000 mA
Output Voltage (Volt) 1.20
Adjustable Output Voltage Yes
Switching Frequency (Hz) 52000
Adjustable Switching Frequency No
Sync Pin No
Efficiency (%) 80
Flyback Yes
Inverting -
Step-up Yes
Step-down -
Datasheet
Title Size in Kbytes Date View Online Download Receive via Email
LM1577 LM2577 Series SIMPLE
SWITCHER Step-Up Voltage
Regulator 889 Kbytes 29-Jun-99 View Online Download Receive via Email
LM1577 Mil-Aero Datasheet
MNLM1577-X-ADJ 23 Kbytes View Online Download Receive via Email
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N/A
-
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.
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
52 kHz internal oscillator
Soft-start function reduces in-rush current during start-up
Output switch protected by current limit, under-voltage lockout, and thermal shutdown
Applications
Simple boost regulator
Flyback and forward regulators
Multiple-output regulator
Design Tools
Title Size in Kbytes Date View Online Download Receive via
Email
SimpleSwitcher® DC-DC
Converters Design Software 10 Kbytes 12-Jun-
2002 View
If you have trouble printing or viewing PDF file(s), see Printing Problems.
[Information as of 5-Aug-2002]
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National P/N LM1577 - SIMPLE SWITCHER Step-Up Voltage Regulator
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National P/N LM2577 - SIMPLE SWITCHER Step-Up Voltage Regulator
See Wireless Products
Products > Analog - Regulators > Simple Switchers > LM2577
LM2577 Product Folder
SIMPLE SWITCHER Step-Up Voltage Regulator
See Also: LM2585 - HIGHER SWITCHING FREQUENCY
LM2586 - ADDITIONAL FEATURES, HIGHER SWITCHING FREQUENCY
Generic P/N 2577
General
Description Features Datasheet Package
& Models Samples
& Pricing Design
Tools Application
Notes
WEBENCH Live Simulation!
LM2577 Webench™ Custom
Design/Analyze/Build It
3.5 <=
V in Lower
V
<=
V in Upper
V
<= 40.0
V out 1.2 <= V<= 300.0
I out A<= 3.00
Ambient Temperature °C <= 100
What is Webench?
Parametric Table
Multiple Output Capability Yes
On/Off Pin No
Error Flag No
Input Voltage, min (Volt) 3.50
Input Voltage, max (Volt) 40
Output Current, max 3000 mA
Output Voltage (Volt) 12, 15
Adjustable Output Voltage No, Yes
Switching Frequency (Hz) 52000
Adjustable Switching Frequency No
Sync Pin No
Efficiency (%) 80
Flyback Yes
Step-up Yes
-
Datasheet
Title Size in
Kbytes Date View Online Download Receive via
Email
LM1577 LM2577 Series SIMPLE SWITCHER Step-Up
Voltage Regulator 889
Kbytes
29-
Jun-
99 View Online Download Receive via
Email
LM1577 LM2577 Series SIMPLE SWITCHER Step-Up
Voltage Regulator (JAPANESE)1149
Kbytes
View Online
Download
Receive via
Email
If you have trouble printing or viewing PDF file(s), see Printing Problems.
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4.5
5.5
12.0
0.50
30
Create This Design
National P/N LM2577 - SIMPLE SWITCHER Step-Up Voltage Regulator
Package Availability, Models, Samples & Pricing
Part Number Package Status Models Samples &
Electronic
Orders
Budgetary
Pricing Std
Pack
Size
Package
Marking
Type Pins MSL SPICE IBIS Qty $US each
LM2577M-12 SOIC
WIDE 24 MSL Full
production N/A N/A
Samples
1K+ $3.1200 rail
of
30
[logo]¢U¢Z¢2¢T
LM2577M
-12 P+
LM2577M-15 SOIC
WIDE 24 MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
30
[logo]¢U¢Z¢2¢T
LM2577M
-15 P+
LM2577M-ADJ SOIC
WIDE 24 MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
30
[logo]¢U¢Z¢2¢T
LM2577M
-ADJ P+
LM2577MX-12 SOIC
WIDE 24 MSL Full
production N/A N/A 1K+ $3.1200 reel
of
1000
[logo]¢U¢Z¢2¢T
LM2577M
-12 P+
LM2577MX-15 SOIC
WIDE 24 MSL Full
production N/A N/A 1K+ $3.1200 reel
of
1000
[logo]¢U¢Z¢2¢T
LM2577M
-15 P+
LM2577MX-
ADJ SOIC
WIDE 24 MSL Full
production N/A N/A 1K+ $3.1200 reel
of
1000
[logo]¢U¢Z¢2¢T
LM2577M
-ADJ P+
LM2577N-12 MDIP 16 MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
20
[logo]¢U¢Z¢3¢T¢P
LM2577N-12
P+
LM2577N-15 MDIP 16 MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
20
[logo]¢U¢Z¢3¢T¢P
LM2577N-15
P+
LM2577N-ADJ MDIP 16 MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
20
[logo]¢U¢Z¢3¢T¢P
LM2577N-ADJ
P+
LM2577T-12 TO 220 5 MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
45
[logo]¢U¢Z¢2¢T
LM2577T-12
P+
LM2577T-15 TO 220 5 MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
45
[logo]¢U¢Z¢2¢T
LM2577T-15
P+
LM2577T-ADJ TO 220 5 MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
45
[logo]¢U¢Z¢2¢T
LM2577T
-ADJ
P+
LM2577S-12 TO 263 5MSL Full
production N/A N/A
Samples
Buy Now
1K+ $3.1200 rail
of
45
[logo]¢U¢Z¢2¢T
LM2577S
-12 P+
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National P/N LM2577 - SIMPLE SWITCHER Step-Up Voltage Regulator
LM2577S-15 TO 263 5MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
45
[logo]¢U¢Z¢2¢T
LM2577S
-15 P+
LM2577S-ADJ TO 263 5MSL Full
production N/A N/A
24 Hour
Samples
Buy Now
1K+ $3.1200 rail
of
45
[logo]¢U¢Z¢2¢T
LM2577S
-ADJ P+
LM2577SX-12 TO 263 5MSL Full
production N/A N/A
Buy Now
1K+ $3.1200 reel
of
500
[logo]¢U¢Z¢2¢T
LM2577S
-12 P+
LM2577SX-15 TO 263 5MSL Full
production N/A N/A 1K+ $3.1200 reel
of
500
[logo]¢U¢Z¢2¢T
LM2577S
-15 P+
LM2577SX-
ADJ TO 263 5MSL Full
production N/A N/A
Buy Now
1K+ $3.1200 reel
of
500
[logo]¢U¢Z¢2¢T
LM2577S
-ADJ P+
LM2577-ADJ
MDC Die Full
production N/A N/A tray
of
N/A -
LM2577-ADJ
MWC Wafer Full
production N/A N/A
wafer
jar
of
N/A
-
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.
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
52 kHz internal oscillator
Soft-start function reduces in-rush current during start-up
Output switch protected by current limit, under-voltage lockout, and thermal shutdown
Applications
file:///H|/imaging/BITTING/cpl/20020808_1/08062002_10/NATL/08062002_HTML/LM2577.html (3 of 4) [Aug-09-2002 12:20:04 PM]
National P/N LM2577 - SIMPLE SWITCHER Step-Up Voltage Regulator
Simple boost regulator
Flyback and forward regulators
Multiple-output regulator
Design Tools
Title Size in Kbytes Date View Online Download Receive via
Email
SimpleSwitcher® DC-DC
Converters Design Software 10 Kbytes 12-Jun-
2002 View
If you have trouble printing or viewing PDF file(s), see Printing Problems.
Application Notes
Title Size in Kbytes Date View Online Download Receive via Email
AN-1061: AN-1061 Power
Conversion in Line-Powered
Equipment 142 Kbytes 5-Jan-97 View Online Download Receive via Email
AN-1229: Application Note 1229
SIMPLE SWITCHER PCB Layout
Guidelines 229 Kbytes 29-Jul-02 View Online Download Receive via Email
AN-776: Application Note 776 20
Watt Simple Switcher Forward
Converter 387 Kbytes 1-May-98 View Online Download Receive via Email
AN-777: Application Note 777
LM2577 Three Output, Isolated
Flyback Regulator 80 Kbytes 1-May-98 View Online Download Receive via Email
If you have trouble printing or viewing PDF file(s), see Printing Problems.
[Information as of 5-Aug-2002]
Search Design Purchasing Quality Company Home
About Languages . Website Guide . About "Cookies" . National is QS 9000 Certified . Privacy/Security Statement .
Contact Us . Site Terms & Conditions of Use . Copyright 2002 © National Semiconductor Corporation . My Preferences .
Feedback
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