LM1577K-883 [NSC]
SIMPLE SWITCHER Step-Up Voltage Regulator; SIMPLE SWITCHER升压型稳压器
| 型号： | LM1577K-883 |
| 厂家： | 
National Semiconductor |
| 描述： | SIMPLE SWITCHER Step-Up Voltage Regulator |
| 文件： | 总27页 (文件大小：891K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
June 1999
LM1577/LM2577 Series
SIMPLE SWITCHER® Step-Up Voltage Regulator
General Description
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
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.
n Soft-start function reduces in-rush current during start-up
n Output switch protected by current limit, under-voltage
lockout, and thermal shutdown
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.
Typical Applications
n Simple boost regulator
n Flyback and forward regulators
n Multiple-output regulator
Typical Application
DS011468-1
Note: Pin numbers shown are for TO-220 (T) package.
Ordering Information
Temperature
Range
Package
Type
Output Voltage
15V
NSC
12V
ADJ
Package Package
Drawing
−40˚C ≤ TA ≤ +125˚C 24-Pin Surface Mount
16-Pin Molded DIP
LM2577M-12
LM2577N-12
LM2577S-12
LM2577T-12
LM2577T-12
Flow LB03
LM2577M-15
LM2577N-15
LM2577S-15
LM2577T-15
LM2577T-15
Flow LB03
LM2577M-ADJ
LM2577N-ADJ
LM2577S-ADJ
LM2577T-ADJ
LM2577T-ADJ
Flow LB03
M24B
N16A
TS5B
T05A
T05D
SO
N
5-Lead Surface Mount
5-Straight Leads
TO-263
TO-220
TO-220
5-Bent Staggered
Leads
−55˚C ≤ TA ≤ +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.
© 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.
Minimum ESD Rating
=
=
(C 100 pF, R 1.5 kΩ)
2 kV
Operating Ratings
Supply Voltage
45V
65V
Supply Voltage
3.5V ≤ VIN ≤ 40V
0V ≤ VSWITCH ≤ 60V
ISWITCH ≤ 3.0A
Output Switch Voltage
Output Switch Current (Note 2)
Power Dissipation
Output Switch Voltage
Output Switch Current
Junction Temperature Range
LM1577
6.0A
Internally Limited
−65˚C to +150˚C
Storage Temperature Range
Lead Temperature
−55˚C ≤ TJ ≤ +150˚C
−40˚C ≤ TJ ≤ +125˚C
LM2577
(Soldering, 10 sec.)
260˚C
150˚C
Maximum Junction Temperature
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, VIN 5V, and ISWITCH 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)
=
VOUT
Output Voltage
VIN 5V to 10V
12.0
V
=
ILOAD 100 mA to 800 mA
11.60/11.40 11.60/11.40
12.40/12.60 12.40/12.60
V(min)
V(max)
mV
(Note 3)
=
Line Regulation
Load Regulation
Efficiency
VIN 3.5V to 10V
20
20
=
ILOAD 300 mA
50/100
50/100
50/100
50/100
mV(max)
mV
=
VIN 5V
=
ILOAD 100 mA to 800 mA
mV(max)
%
=
=
η
VIN 5V, ILOAD 800 mA
80
7.5
25
DEVICE PARAMETERS
=
IS
Input Supply Current
VFEEDBACK 14V (Switch Off)
mA
mA(max)
mA
10.0/14.0
50/85
10.0/14.0
50/85
=
ISWITCH 2.0A
=
VCOMP 2.0V (Max Duty Cycle)
mA(max)
V
=
VUV
Input Supply
ISWITCH 100 mA
2.90
Undervoltage Lockout
2.70/2.65
3.10/3.15
2.70/2.65
3.10/3.15
V(min)
V(max)
kHz
fO
Oscillator Frequency
Measured at Switch Pin
52
=
ISWITCH 100 mA
48/42
56/62
48/42
56/62
kHz(min)
kHz(max)
V
VREF
Output Reference
Voltage
Measured at Feedback Pin
=
VIN 3.5V to 40V
12
7
11.76/11.64 11.76/11.64
12.24/12.36 12.24/12.36
V(min)
V(max)
mV
=
VCOMP 1.0V
=
VIN 3.5V to 40V
Output Reference
Voltage Line Regulator
RFB
GM
Feedback Pin Input
Resistance
9.7
kΩ
=
Error Amp
ICOMP −30 µA to +30 µA
370
µmho
µmho(min)
µmho(max)
V/V
=
Transconductance
VCOMP 1.0V
225/145
515/615
225/145
515/615
=
AVOL
Error Amp
VCOMP 1.1V to 1.9V
80
=
Voltage Gain
RCOMP 1.0 MΩ
50/25
50/25
V/V(min)
(Note 7)
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2
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, VIN 5V, and ISWITCH 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
0.3
V
V(min)
V
=
Output Swing
VFEEDBACK 10.0V
2.2/2.0
2.2/2.0
Lower Limit
=
VFEEDBACK 15.0V
0.40/0.55
0.40/0.55
V(max)
µA
=
±
200
Error Amplifier
Output Current
VFEEDBACK 10.0V to 15.0V
=
±
±
±
±
VCOMP 1.0V
130/ 90
130/ 90
µA(min)
µA(max)
µA
±
±
±
±
300/ 400
300/ 400
=
ISS
Soft Start Current
VFEEDBACK 10.0V
5.0
=
VCOMP 0V
2.5/1.5
7.5/9.5
2.5/1.5
7.5/9.5
µA(min)
µA(max)
%
=
D
Maximum Duty Cycle
VCOMP 1.5V
95
=
ISWITCH 100 mA
93/90
93/90
%(min)
A/V
Switch
Transconductance
12.5
=
IL
Switch Leakage
Current
VSWITCH 65V
10
0.5
4.5
µA
µA(max)
V
=
VFEEDBACK 15V (Switch Off)
300/600
0.7/0.9
300/600
0.7/0.9
=
ISWITCH 2.0A
VSAT
Switch Saturation
Voltage
=
VCOMP 2.0V (Max Duty Cycle)
V(max)
A
NPN Switch
Current Limit
3.7/3.0
5.3/6.0
3.7/3.0
5.3/6.0
A(min)
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, VIN 5V, and ISWITCH 0.
LM1577-15
Limit
LM2577-15
Limit
Units
Symbol
Parameter
Conditions
Typical
(Limits)
(Notes 3, 4)
(Note 5)
SYSTEM PARAMETERS Circuit of Figure 2 (Note 6)
=
VOUT
Output Voltage
VIN 5V to 12V
15.0
V
=
ILOAD 100 mA to 600 mA
14.50/14.25 14.50/14.25
15.50/15.75 15.50/15.75
V(min)
V(max)
mV
(Note 3)
=
Line Regulation
Load Regulation
Efficiency
VIN 3.5V to 12V
20
20
50/100
50/100
50/100
50/100
=
ILOAD 300 mA
mV(max)
mV
=
VIN 5V
=
ILOAD 100 mA to 600 mA
mV(max)
%
=
=
η
VIN 5V, ILOAD 600 mA
80
7.5
25
DEVICE PARAMETERS
=
IS
Input Supply Current
VFEEDBACK 18.0V
mA
(Switch Off)
10.0/14.0
50/85
10.0/14.0
50/85
mA(max)
mA
=
ISWITCH 2.0A
=
VCOMP 2.0V
mA(max)
(Max Duty Cycle)
=
VUV
Input Supply
ISWITCH 100 mA
2.90
V
3
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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, VIN 5V, and ISWITCH 0.
LM1577-15
Limit
LM2577-15
Limit
Units
Symbol
Parameter
Conditions
Typical
(Limits)
(Notes 3, 4)
(Note 5)
DEVICE PARAMETERS
Undervoltage
2.70/2.65
3.10/3.15
2.70/2.65
3.10/3.15
V(min)
V(max)
kHz
Lockout
fO
Oscillator Frequency
Measured at Switch Pin
52
=
ISWITCH 100 mA
48/42
56/62
48/42
56/62
kHz(min)
kHz(max)
V
VREF
Output Reference
Voltage
Measured at Feedback Pin
=
VIN 3.5V to 40V
15
10
14.70/14.55 14.70/14.55
15.30/15.45 15.30/15.45
V(min)
V(max)
mV
=
VCOMP 1.0V
=
VIN 3.5V to 40V
Output Reference
Voltage Line Regulation
RFB
GM
Feedback Pin Input
Voltage Line Regulator
Error Amp
12.2
300
kΩ
=
ICOMP −30 µA to +30 µA
µmho
µmho(min)
µmho(max)
V/V
=
Transconductance
VCOMP 1.0V
170/110
420/500
170/110
420/500
=
AVOL
Error Amp
VCOMP 1.1V to 1.9V
65
=
Voltage Gain
RCOMP 1.0 MΩ
40/20
40/20
V/V(min)
(Note 7)
Error Amplifier
Output Swing
Upper Limit
2.4
0.3
V
V(min)
V
=
VFEEDBACK 12.0V
2.2/2.0
2.2/2.0
Lower Limit
=
VFEEDBACK 18.0V
0.4/0.55
0.40/0.55
V(max)
µA
=
±
200
Error Amp
VFEEDBACK 12.0V to 18.0V
=
±
±
±
±
Output Current
VCOMP 1.0V
130/ 90
130/ 90
µA(min)
µA(max)
µA
±
±
±
±
300/ 400
300/ 400
=
ISS
Soft Start Current
VFEEDBACK 12.0V
5.0
=
VCOMP 0V
2.5/1.5
7.5/9.5
2.5/1.5
7.5/9.5
µA(min)
µA(max)
%
=
D
Maximum Duty
Cycle
VCOMP 1.5V
95
=
ISWITCH 100 mA
93/90
93/90
%(min)
A/V
Switch
Transconductance
12.5
=
IL
Switch Leakage
Current
VSWITCH 65V
10
0.5
4.3
µA
=
VFEEDBACK 18.0V
300/600
0.7/0.9
300/600
0.7/0.9
µA(max)
(Switch Off)
=
VSAT
Switch Saturation
Voltage
ISWITCH 2.0A
V
=
VCOMP 2.0V
V(max)
(Max Duty Cycle)
=
NPN Switch
Current Limit
VCOMP 2.0V
A
3.7/3.0
5.3/6.0
3.7/3.0
5.3/6.0
A(min)
A(max)
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4
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, VIN 5V, VFEEDBACK VREF, and ISWITCH 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)
=
VOUT
Output Voltage
VIN 5V to 10V
12.0
V
V(min)
V(max)
mV
=
ILOAD 100 mA to 800 mA
11.60/11.40
12.40/12.60
11.60/11.40
12.40/12.60
(Note 3)
=
∆VOUT
∆VIN
/
/
Line Regulation
Load Regulation
Efficiency
VIN 3.5V to 10V
20
20
=
ILOAD 300 mA
50/100
50/100
50/100
50/100
mV(max)
mV
=
VIN 5V
∆VOUT
=
∆ILOAD
ILOAD 100 mA to 800 mA
mV(max)
%
=
=
η
VIN 5V, ILOAD 800 mA
80
DEVICE PARAMETERS
=
IS
Input Supply Current
VFEEDBACK 1.5V (Switch Off)
7.5
25
mA
mA(max)
mA
10.0/14.0
50/85
10.0/14.0
50/85
=
ISWITCH 2.0A
=
VCOMP 2.0V (Max Duty Cycle)
mA(max)
V
=
VUV
Input Supply
ISWITCH 100 mA
2.90
Undervoltage Lockout
2.70/2.65
3.10/3.15
2.70/2.65
3.10/3.15
V(min)
V(max)
kHz
fO
Oscillator Frequency
Measured at Switch Pin
52
=
ISWITCH 100 mA
48/42
56/62
48/42
56/62
kHz(min)
kHz(max)
V
VREF
Reference
Voltage
Measured at Feedback Pin
=
VIN 3.5V to 40V
1.230
0.5
1.214/1.206
1.246/1.254
1.214/1.206
1.246/1.254
V(min)
V(max)
mV
=
VCOMP 1.0V
=
VIN 3.5V to 40V
∆VREF
∆VIN
IB
/
Reference Voltage
Line Regulation
Error Amp
=
VCOMP 1.0V
100
nA
nA(max)
µmho
µmho(min)
µmho(max)
V/V
Input Bias Current
Error Amp
300/800
300/800
=
GM
ICOMP −30 µA to +30 µA
3700
=
Transconductance
VCOMP 1.0V
2400/1600
4800/5800
2400/1600
4800/5800
=
AVOL
Error Amp
VCOMP 1.1V to 1.9V
800
2.4
0.3
=
Voltage Gain
Error Amplifier
Output Swing
RCOMP 1.0 MΩ (Note 7)
500/250
2.2/2.0
500/250
2.2/2.0
V/V(min)
V
Upper Limit
=
VFEEDBACK 1.0V
V(min)
V
Lower Limit
=
VFEEDBACK 1.5V
0.40/0.55
0.40/0.55
V(max)
µA
=
±
200
Error Amp
VFEEDBACK 1.0V to 1.5V
=
±
±
±
±
Output Current
VCOMP 1.0V
130/ 90
130/ 90
µA(min)
µA(max)
µA
±
±
±
±
300/ 400
300/ 400
=
ISS
Soft Start Current
VFEEDBACK 1.0V
5.0
=
VCOMP 0V
2.5/1.5
7.5/9.5
2.5/1.5
7.5/9.5
µA(min)
µA(max)
%
=
D
Maximum Duty Cycle
VCOMP 1.5V
95
=
ISWITCH 100 mA
93/90
93/90
%(min)
A/V
∆ISWITCH
/
Switch
12.5
∆VCOMP
Transconductance
5
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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, VIN 5V, VFEEDBACK VREF, and ISWITCH 0.
LM1577-ADJ LM2577-ADJ
Units
Symbol
Parameter
Conditions
Typical
Limit
Limit
(Limits)
(Notes 3, 4)
(Note 5)
DEVICE PARAMETERS
=
IL
Switch Leakage
VSWITCH 65V
10
0.5
4.3
µA
µA(max)
V
=
Current
VFEEDBACK 1.5V (Switch Off)
300/600
0.7/0.9
300/600
0.7/0.9
=
ISWITCH 2.0A
VSAT
Switch Saturation
Voltage
=
VCOMP 2.0V (Max Duty Cycle)
V(max)
A
=
VCOMP 2.0V
NPN Switch
Current Limit
3.7/3.0
5.3/6.0
3.7/3.0
5.3/6.0
A(min)
A(max)
THERMAL PARAMETERS (All Versions)
θJA
θJC
θJA
θJC
θJA
Thermal Resistance
K Package, Junction to Ambient
K Package, Junction to Case
T Package, Junction to Ambient
T Package, Junction to Case
N Package, Junction to
Ambient (Note 8)
35
1.5
65
2
85
˚C/W
θJA
M Package, Junction
100
37
to Ambient (Note 8)
θJA
S Package, Junction to
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% 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 MΩ resistor is connected to the compensation pin (which is the error amplifier’s output) to ensure accuracy in measuring A
. In actual applications,
VOL
this pin’s load resistance should be ≥10 MΩ, resulting in A
VOL
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, θ is 50˚C/W; with 1 square inch of copper area, θ is 37˚C/W; and with 1.6 or more square inches of copper area, θ is 32˚C/W.
JA JA JA
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6
Typical Performance Characteristics
Reference Voltage
vs Temperature
Reference Voltage
vs Temperature
Reference Voltage
vs Temperature
DS011468-34
DS011468-35
DS011468-36
∆ Reference Voltage
∆ Reference Voltage
∆ Reference Voltage
vs Supply Voltage
vs Supply Voltage
vs Supply Voltage
DS011468-37
DS011468-38
DS011468-39
Error Amp Transconductance
vs Temperature
Error Amp Transconductance
vs Temperature
Error Amp Transconductance
vs Temperature
DS011468-40
DS011468-41
DS011468-42
7
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Typical Performance Characteristics (Continued)
Error Amp Voltage
Error Amp Voltage
Error Amp Voltage
Gain vs Temperature
Gain vs Temperature
Gain vs Temperature
DS011468-43
DS011468-46
DS011468-49
DS011468-44
DS011468-47
DS011468-50
DS011468-45
DS011468-48
DS011468-51
Quiescent Current
vs Temperature
Quiescent Current
vs Switch Current
Current Limit
vs Temperature
Current Limit Response
Time vs Overdrive
Switch Saturation Voltage
vs Switch Current
Switch Transconductance
vs Temperature
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8
Typical Performance Characteristics (Continued)
Feedback Pin Bias
Current vs Temperature
Oscillator Frequency
vs Temperature
DS011468-52
DS011468-53
Maximum Power Dissipation
(TO-263) (Note 9)
DS011468-31
Connection Diagrams
Straight Leads
5-Lead TO-220 (T)
Bent, Staggered Leads
5-Lead TO-220 (T)
DS011468-4
DS011468-5
Top View
Top View
Order Number LM2577T-12, LM2577T-15,
or LM2577T-ADJ
Order Number LM2577T-12 Flow LB03, LM2577T-15
Flow LB03, or LM2577T-ADJ Flow LB03
See NS Package Number T05D
See NS Package Number T05A
9
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Connection Diagrams (Continued)
16-Lead DIP (N)
24-Lead Surface Mount (M)
DS011468-6
*
No internal Connection
Top View
Order Number LM2577N-12, LM2577N-15,
or LM2577N-ADJ
DS011468-7
See NS Package Number N16A
*
No internal Connection
Top View
Order Number LM2577M-12, LM2577M-15,
or LM2577M-ADJ
See NS Package Number M24B
TO-263 (S)
4-Lead TO-3 (K)
5-Lead Surface-Mount Package
DS011468-32
Top View
DS011468-8
Bottom View
Order Number LM1577K-12/883, LM1577K-15/883,
or LM1577K-ADJ/883
DS011468-33
Side View
Order Number LM2577S-12, LM2577S-15,
or LM2577S-ADJ
See NS Package Number K04A
See NS Package Number TS5B
www.national.com
10
LM1577-12, LM2577-12 Test Circuit
DS011468-30
DS011468-26
DS011468-9
=
=
L
D
C
415-0930 (AIE)
any manufacturer
=
Sprague Type 673D
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
D
C
415-0930 (AIE)
any manufacturer
=
Sprague Type 673D
OUT
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
LM1577-ADJ, LM2577-ADJ Test Circuit
=
L
415-0930 (AIE)
=
D
C
any manufacturer
=
Sprague Type 673D
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
11
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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
www.national.com
12
Application Hints (Continued)
Duty Cycle
D
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.
Average
Inductor
Current
IIND(AVE)
Inductor
Current
Ripple
∆IIND
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 VIN/L, storing current in the inductor. When the
Peak
Inductor
Current
IIND(PK)
Peak Switch
Current
ISW(PK)
switch turns off, the lower end of the inductor flies above VIN
,
discharging its current through diode (D) into the output ca-
pacitor (COUT) at a rate of (VOUT − VIN)/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).
Switch
Voltage
When Off
VSW(OFF)
VOUT + VF
VOUT − VSAT
ILOAD
Diode
Reverse
Voltage
VR
Average
Diode
Current
ID(AVE)
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.
Peak Diode
Current
ID(PK)
Power
Dissipation
of
Voltage and current waveforms for this circuit are shown in
Figure 5, and formulas for calculating them are given in Fig-
ure 6.
PD
LM1577/2577
=
V
F
Forward Biased Diode Voltage
=
I
Output Load Current
LOAD
FIGURE 6. Step-Up Regulator Formulas
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:
=
VIN (min) Minimum input supply voltage
=
VOUT Regulated output voltage
=
ILOAD(max) Maximum output load current
Before proceeding any further, determine if the LM1577/
LM2577 can provide these values of VOUT and ILOAD(max)
when operating with the minimum value of VIN. The upper
limits for VOUT and ILOAD(max) are given by the following
equations.
DS011468-11
FIGURE 5. Step-Up Regulator Waveforms
VOUT ≤ 60V
and VOUT ≤ 10 x VIN(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
13
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If LMIN 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:
Application Hints (Continued)
From Figure 7 (for 12V output) or Figure 8 (for 15V
output), identify inductor code for region indicated by
VIN
and ILOAD (max). The shaded region indicates
(min)
1. Find the lowest value inductor that is greater than LMIN
.
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.
2. Find where E•T intersects this inductor value to determine
if it has an L or H prefix. If E•T intersects both the L and H re-
gions, select the inductor with an H prefix.
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 ≤ D ≤ 0.9):
=
where VF 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:
DS011468-27
FIGURE 7. LM2577-12 Inductor Selection Guide
IIND,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 E•T and IIND,DC
.
This code gives the inductor value in microhenries. The
L or H prefix signifies whether the inductor is rated for a
maximum E•T of 90 V•µs (L) or 250 V•µs (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:
DS011468-28
FIGURE 8. LM2577-15 Inductor Selection Guide
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14
Application Hints (Continued)
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
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 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 gener-
ate more EMI than the other types, and this may inter-
fere with signals sensitive to noise.
15
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Application Hints (Continued)
Inductor
Code
L47
Manufacturer’s Part Number
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 CC ≥ 0.22 µF.
Schott
Pulse
Renco
RL2442
RL2443
RL2444
RL1954
RL1953
RL1952
RL1951
RL1950
RL2445
RL2446
RL2447
RL1961
RL1960
RL1959
RL1958
RL2448
67126980
67126990
67127000
67127010
67127020
67127030
67127040
67127050
67127060
67127070
67127080
67127090
67127100
67127110
67127120
67127130
PE - 53112
PE - 92114
PE - 92108
PE - 53113
PE - 52626
PE - 52627
PE - 53114
PE - 52629
PE - 53115
PE - 53116
PE - 53117
PE - 53118
PE - 53119
PE - 53120
PE - 53121
PE - 53122
L68
L100
L150
L220
L330
L470
L680
H150
H220
H330
H470
H680
H1000
H1500
H2200
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
Schott Corp., (612) 475-1173
1000 Parkers Lake Rd., Wayzata, MN 55391
Pulse Engineering, (619) 268-2400
Choose a capacitor that is rated at least 50% higher than this
value at 52 kHz.
P.O. Box 12235, San Diego, CA 92112
Renco Electronics Inc., (516) 586-5566
60 Jeffryn Blvd. East, Deer Park, NY 11729
Equivalent Series Resistance (ESR) : This is the primary
cause of output ripple voltage, and it also affects the values
of RC and CC needed to stabilize the regulator. As a result,
the preceding calculations for CC and RC are only valid if
ESR doesn’t exceed the maximum value specified by the fol-
lowing equations.
FIGURE 10. Table of Standardized Inductors and
Manufacturer’s Part Numbers
2. Compensation Network (RC, CC) and Output Capacitor
(COUT) Selection
RC and CC form a pole-zero compensation network that sta-
bilizes the regulator. The values of RC and CC are mainly de-
pendant on the regulator voltage gain, ILOAD(max), L and
C
OUT. The following procedure calculates values for RC, CC,
and COUT that ensure regulator stability. Be aware that this
procedure doesn’t necessarily result in RC and CC 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 VOUT tran-
sient response when pulsing ILOAD (see Figure 15).
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.
A. First, calculate the maximum value for RC.
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.
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 COUT 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 CC
.
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16
Application Hints (Continued)
VOUT
(max)
20V
Schottky
Fast Recovery
3. Output Voltage Selection (R1 and R2)
1A
1N5817
3A
1A
3A
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.
1N5820
MBR120P MBR320P
1N5818 1N5821
MBR130P MBR330P
With the LM1577-ADJ/LM2577-ADJ, the output voltage is
given by
30V
40V
=
VOUT 1.23V (1 + R1/R2)
11DQ03
1N5819
31DQ03
1N5822
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 VOUT
,
MBR140P MBR340P
select R1 and R2 so that
11DQ04
MBR150
11DQ05
31DQ04
MBR350
31DQ05
1N4933
MUR105
1N4934
HER102
MUR110
10DL1
50V
MR851
30DL1
4. Input Capacitor Selection (CIN
)
100V
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.
MR831
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 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
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 ILOAD(max)
and ID(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.
17
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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
DS011468-16
A: Switch pin voltage, 10 V/div
DS011468-15
B: Switch pin current, 2 A/div
C: Inductor current, 2 A/div
A: Output Voltage Change, 100 mV/div. (AC-coupled)
B: Load current, 0.2 A/div
D: Output ripple voltage, 100 mV/div (AC-coupled)
Horizontal: 5 µs/div
Horizontal: 5 ms/div
FIGURE 15. Load Transient Response of Step-Up
FIGURE 16. Switching Waveforms of Step-Up
Regulator of Figure 13
Regulator of Figure 13
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18
A. First, calculate the maximum value for RC.
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.
∑
Where ILOAD(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 kΩ.
∑
B. Calculate the minimum value for COUT (sum of COUT
at both outputs) using the following two equations.
The larger of these two values must be used to ensure regu-
lator stability.
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
20lists these transformers with the input voltage, output volt-
ages and maximum load current they are designed for.
2. Compensation Network (CC, RC) and
Output Capacitor (COUT) Selection
As explained in the Step-Up Regulator Design Procedure,
CC, RC and COUT 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
DS011468-17
FIGURE 17. Flyback Regulator Waveforms
∑
single output regulator by changing ILOAD(max) to ILOAD(max)
in the following equations.
DS011468-18
=
T1 Pulse Engineering, PE-65300
=
D1, D2 1N5821
±
FIGURE 18. LM1577-ADJ/LM2577-ADJ Flyback Regulator with Outputs
19
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Application Hints (Continued)
Duty Cycle
D
Primary Current Variation
Peak Primary Current
∆IP
IP(PK)
Switch Voltage when Off
VSW(OFF)
+
−
Diode Reverse Voltage
Average Diode Current
Peak Diode Current
VR
VOUT N (VIN VSAT
ILOAD
)
ID(AVE)
ID(PK)
Short Circuit Diode Current
Power Dissipation of
LM1577/LM2577
PD
DS011468-78
FIGURE 19. Flyback Regulator Formulas
C. Calculate the minimum value of CC
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 VOUT, select
R1 and R2 so that
D. Calculate the maximum ESR of the +VOUT and −VOUT
output capacitors in parallel.
4. Diode Selection
The switching diode in a flyback converter must withstand
the reverse voltage specified by the following equation.
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
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.
selection of COUT
.
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.
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 VIN 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 VIN and Ground pins.
With the LM1577-ADJ/LM2577-ADJ, the output voltage is
given by
=
VOUT 1.23V (1 + R1/R2)
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20
RC values are selected for switch clamp voltage (VCLAMP
that is 5V to 10V greater than VSW(OFF). Use the following
equations to calculate R and C;
)
Application Hints (Continued)
Dual
Maxi-
Transformer
Type
Input
mum
Voltage
Output
Output
Current
325 mA
275 mA
225 mA
700 mA
575 mA
500 mA
800 mA
700 mA
575 mA
900 mA
825 mA
700 mA
Voltage
=
±
±
±
±
±
±
±
±
±
±
±
±
LP 100 µH
5V
10V
12V
15V
10V
12V
15V
10V
12V
15V
10V
12V
15V
=
1
2
3
N
1
5V
Power dissipation (and power rating) of the resistor is;
The fast recovery diode must have a reverse voltage rating
5V
10V
10V
10V
12V
12V
12V
15V
15V
15V
=
LP 200 µH
=
N
0.5
greater than VCLAMP
.
=
LP 250 µH
=
N
0.5
Transformer
Manufacturers’ Part Numbers
Type
AIE
Pulse
Renco
RL-2580
RL-2581
RL-2582
1
2
3
326-0637
330-0202
330-0203
PE-65300
PE-65301
PE-65302
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 inter-
fere with other circuits connected to the same input supply
voltage.
DS011468-19
FIGURE 21. Snubber Circuit
FLYBACK REGULATOR CIRCUIT EXAMPLE
6. Snubber Circuit
±
The circuit of Figure 22 produces 15V (at 225 mA each)
A “snubber” circuit is required when operating from input
voltages greater than 10V, or when using a transformer with
LP ≥ 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
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.
21
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Application Hints (Continued)
DS011468-20
=
T1 Pulse Engineering, PE-65300
=
D1, D2 1N5821
FIGURE 22. Flyback Regulator Easily Provides Dual Outputs
DS011468-21
DS011468-22
FIGURE 23. Line Regulation (Typical) of Flyback
Regulator of Figure 22, +15V Output
FIGURE 25. Line Regulation (Typical) of Flyback
Regulator of Figure 22, −15V Output
DS011468-24
DS011468-23
A: Output Voltage Change, 100 mV/div
B: Output Current, 100 mA/div
Horizontal: 10 ms/div
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
FIGURE 24. Load Transient Response of Flyback
Regulator of Figure 22, +15V Output
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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 60Ω
23
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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
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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
25
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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
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26
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
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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
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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.
相关型号：
LM1578AH
IC 0.75 A SWITCHING REGULATOR, 100 kHz SWITCHING FREQ-MAX, MBCY8, METAL CAN, TO-99, 8 PIN, Switching Regulator or Controller
NSC
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