LM2588-12MWC [NSC]
IC 9.5 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, UUC, WAFER, Switching Regulator or Controller;
| 型号： | LM2588-12MWC |
| 厂家： | 
National Semiconductor |
| 描述： | IC 9.5 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, UUC, WAFER, Switching Regulator or Controller 开关 |
| 文件： | 总34页 (文件大小：870K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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April 1998
LM2588
SIMPLE SWITCHER® 5A Flyback Regulator with
Shutdown
General Description
Features
n Requires few external components
n Family of standard inductors and transformers
n NPN output switches 5.0A, can stand off 65V
n Wide input voltage range: 4V to 40V
The LM2588 series of regulators are monolithic integrated
circuits specifically designed for flyback, step-up (boost), and
forward converter applications. The device is available in 4
different output voltage versions: 3.3V, 5.0V, 12V, and adjust-
able.
n Adjustable switching frequency: 100 kHz to 200 kHz
n External shutdown capability
n Draws less than 60 µA when shut down
n Frequency synchronization
n Current-mode operation for improved transient
response, line regulation, and current limit
n Internal soft-start function reduces in-rush current during
start-up
n Output transistor protected by current limit, under
voltage lockout, and thermal shutdown
Requiring a minimum number of external components, these
regulators are cost effective, and simple to use. Included in
the datasheet are typical circuits of boost and flyback regula-
tors. Also listed are selector guides for diodes and capacitors
and a family of standard inductors and flyback transformers
designed to work with these switching regulators.
The power switch is a 5.0A NPN device that can stand-off
65V. Protecting the power switch are current and thermal
limiting circuits, and an undervoltage lockout circuit. This IC
contains an adjustable frequency oscillator that can be pro-
grammed up to 200 kHz. The oscillator can also be synchro-
nized with other devices, so that multiple devices can oper-
ate at the same switching frequency.
±
n System output voltage tolerance of 4% max over line
and load conditions
Typical Applications
n Flyback regulator
n Forward converter
n Multiple-output regulator
n Simple boost regulator
Other features include soft start mode to reduce in-rush cur-
rent during start up, and current mode control for improved
rejection of input voltage and output load transients and
cycle-by-cycle current limiting. The device also has a shut-
down pin, so that it can be turned off externally. An output
±
voltage tolerance of 4%, within specified input voltages and
output load conditions, is guaranteed for the power supply
system.
Flyback Regulator
DS012420-1
®
SIMPLE SWITCHER® and Switchers Made Simple are registered trademarks of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation
DS012420
www.national.com
Ordering Information
Package Type
NSC Package
Drawing
TA07B
Order Number
7-Lead TO-220 Bent, Staggered Leads
7-Lead TO-263
LM2588T-3.3, LM2588T-5.0, LM2588T-12, LM2588T-ADJ
LM2588S-3.3, LM2588S-5.0, LM2588S-12, LM2588S-ADJ
TS7B
7-Lead TO-263 Tape and Reel
TS7B
LM2588SX-3.3, LM2588SX-5.0, LM2588SX-12,
LM2588SX-ADJ
www.national.com
2
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Lead Temperature
(Soldering, 10 sec.)
Maximum Junction Temperature
(Note 3)
260˚C
150˚C
2 kV
Minimum ESD Rating
Input Voltage
−0.4V ≤ VIN ≤ 45V
−0.4V ≤ VSW ≤ 65V
Internally Limited
=
=
(C 100 pF, R 1.5 kΩ)
Switch Voltage
Switch Current (Note 2)
Compensation Pin Voltage
Feedback Pin Voltage
ON /OFF Pin Voltage
Sync Pin Voltage
Operating Ratings
Supply Voltage
−0.4V ≤ VCOMP ≤ 2.4V
−0.4V ≤ VFB ≤ 2 VOUT
−0.4V ≤ VSH ≤ 6V
−0.4V ≤ VSYNC ≤ 2V
Internally Limited
4V ≤ VIN ≤ 40V
0V ≤ VSW ≤ 60V
ISW ≤ 5.0A
Output Switch Voltage
Output Switch Current
Junction Temperature Range
Power Dissipation (Note 3)
Storage Temperature Range
−40˚C ≤ TJ ≤ +125˚C
−65˚C to +150˚C
LM2588-3.3
Electrical Characteristics
=
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.
Symbol Parameters Conditions
SYSTEM PARAMETERS Test Circuit of Figure 1 (Note 4)
Typical
3.3
Min
Max
3.43/3.46
50/100
50/100
Units
V
=
VOUT
Output Voltage
Line Regulation
Load Regulation
Efficiency
VIN 4V to 12V
3.17/3.14
=
ILOAD 400 mA to 1.75A
=
∆VOUT
∆VIN
/
/
VIN 4V to 12V
20
mV
mV
%
=
ILOAD 400 mA
=
∆VOUT
VIN 12V
20
=
ILOAD 400 mA to 1.75A
∆ILOAD
=
=
η
VIN 12V, ILOAD 1A
75
UNIQUE DEVICE PARAMETERS (Note 5)
VREF
∆VREF
GM
Output Reference
Voltage
Measured at Feedback Pin
3.3
3.242/3.234
3.358/3.366
V
=
VCOMP 1.0V
=
Reference Voltage
Line Regulation
Error Amp
VIN 4V to 40V
2.0
mV
mmho
V/V
=
ICOMP −30 µA to +30 µA
1.193
260
0.678
2.259
=
VCOMP 1.0V
Transconductance
Error Amp
=
AVOL
VCOMP 0.5V to 1.6V
151/75
=
RCOMP 1.0 MΩ (Note 6)
Voltage Gain
LM2588-5.0
Electrical Characteristics
=
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.
Symbol Parameters Conditions
SYSTEM PARAMETERS Test Circuit of Figure 1 (Note 4)
Typical
5.0
Min
Max
5.20/5.25
50/100
50/100
Units
V
=
VOUT
Output Voltage
Line Regulation
Load Regulation
Efficiency
VIN 4V to 12V
4.80/4.75
=
ILOAD 500 mA to 1.45A
=
∆VOUT
∆VIN
/
/
VIN 4V to 12V
20
mV
mV
%
=
ILOAD 500 mA
=
∆VOUT
VIN 12V
20
=
ILOAD 500 mA to 1.45A
∆ILOAD
=
=
η
VIN 12V, ILOAD 750 mA
80
UNIQUE DEVICE PARAMETERS (Note 5)
VREF
Output Reference
Voltage
Measured at Feedback Pin
5.0
4.913/4.900
5.088/5.100
V
=
VCOMP 1.0V
3
www.national.com
LM2588-5.0
Electrical Characteristics (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.
Symbol Parameters Conditions
UNIQUE DEVICE PARAMETERS (Note 5)
Typical
3.3
Min
Max
Units
mV
=
VIN 4V to 40V
∆VREF
Reference Voltage
Line Regulation
Error Amp
=
GM
ICOMP −30 µA to +30 µA
0.750
165
0.447
1.491
mmho
V/V
=
VCOMP 1.0V
Transconductance
Error Amp
=
AVOL
VCOMP 0.5V to 1.6V
99/49
=
RCOMP 1.0 MΩ (Note 6)
Voltage Gain
LM2588-12
Electrical Characteristics
=
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.
Symbol Parameters Conditions
SYSTEM PARAMETERS Test Circuit of Figure 2 (Note 4)
Typical
12.0
20
Min
Max
Units
V
=
VOUT
Output Voltage
Line Regulation
Load Regulation
Efficiency
VIN 4V to 10V
11.52/11.40
12.48/12.60
100/200
=
ILOAD 300 mA to 1.2A
=
∆VOUT
∆VIN
/
/
VIN 4V to 10V
mV
mV
%
=
ILOAD 300 mA
=
∆VOUT
VIN 10V
20
100/200
=
ILOAD 300 mA to 1.2A
∆ILOAD
=
=
η
VIN 10V, ILOAD 1A
90
UNIQUE DEVICE PARAMETERS (Note 5)
VREF
∆VREF
GM
Output Reference
Voltage
Measured at Feedback Pin
12.0
7.8
11.79/11.76
12.21/12.24
V
=
VCOMP 1.0V
=
Reference Voltage
Line Regulation
Error Amp
VIN 4V to 40V
mV
mmho
V/V
=
ICOMP −30 µA to +30 µA
0.328
70
0.186
0.621
=
VCOMP 1.0V
Transconductance
Error Amp
=
AVOL
VCOMP 0.5V to 1.6V
41/21
=
RCOMP 1.0 MΩ (Note 6)
Voltage Gain
LM2588-ADJ
Electrical Characteristics
=
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.
Symbol Parameters
SYSTEM PARAMETERS Test Circuit of Figure 2 (Note 4)
Conditions
Typical
12.0
20
Min
Max
Units
V
=
VOUT
Output Voltage
Line Regulation
Load Regulation
Efficiency
VIN 4V to 10V
11.52/11.40
12.48/12.60
100/200
=
ILOAD 300 mA to 1.2A
=
∆VOUT
∆VIN
/
/
VIN 4V to 10V
mV
mV
%
=
ILOAD 300 mA
=
∆VOUT
VIN 10V
20
100/200
=
ILOAD 300 mA to 1.2A
∆ILOAD
=
=
η
VIN 10V, ILOAD 1A
90
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4
LM2588-ADJ
Electrical Characteristics (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.
Symbol Parameters
UNIQUE DEVICE PARAMETERS (Note 5)
Conditions
Typical
1.230
1.5
Min
Max
Units
V
VREF
∆VREF
GM
Output Reference
Voltage
Measured at Feedback Pin
1.208/1.205
1.252/1.255
=
VCOMP 1.0V
=
Reference Voltage
Line Regulation
Error Amp
VIN 4V to 40V
mV
=
ICOMP −30 µA to +30 µA
3.200
670
1.800
6.000
mmho
V/V
nA
=
VCOMP 1.0V
Transconductance
Error Amp
=
AVOL
VCOMP 0.5V to 1.6V
400/200
=
RCOMP 1.0 MΩ (Note 6)
Voltage Gain
Error Amp
=
IB
VCOMP 1.0V
125
425/600
Input Bias Current
All Output Voltage Versions
Electrical Characteristics (Note 5)
=
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.
Symbol
IS
Parameters
Conditions
Typical
Min
Max
Units
Input Supply Current Switch Off
(Note 8)
11
15.5/16.5
mA
=
ISWITCH 3.0A
85
16
140/165
100/300
mA
µA
=
VSH 3V
IS/D
Shutdown Input
Supply Current
Input Supply
=
VUV
RLOAD 100Ω
3.30
3.05
3.75
V
Undervoltage
Lockout
fO
Oscillator Frequency Measured at Switch Pin
=
=
RLOAD 100Ω, VCOMP 1.0V
100
200
25
85/75
115/125
kHz
kHz
kHz
V
Freq. Adj. Pin Open (Pin 1)
=
RSET 22 kΩ
fSC
Short-Circuit
Frequency
Measured at Switch Pin
=
RLOAD 100Ω
=
VFEEDBACK 1.15V
VEAO
Error Amplifier
Output Swing
Upper Limit
(Note 7)
2.8
2.6/2.4
Lower Limit
(Note 8)
0.25
0.40/0.55
V
IEAO
Error Amp
(Note 9)
Output Current
(Source or Sink)
Soft Start Current
165
11.0
98
110/70
8.0/7.0
93/90
260/320
µA
µA
%
=
ISS
VFEEDBACK 0.92V
17.0/19.0
=
VCOMP 1.0V
=
DMAX
Maximum Duty
Cycle
RLOAD 100Ω
(Note 7)
IL
Switch Leakage
Current
Switch Off
15
300/600
µA
V
=
VSWITCH 60V
=
VSUS
Switch Sustaining
Voltage
dV/dT 1.5V/ns
65
5
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All Output Voltage Versions
Electrical Characteristics (Note 5) (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.
Symbol
Parameters
Conditions
Typical
Min
Max
Units
=
VSAT
Switch Saturation
Voltage
ISWITCH 5.0A
0.7
1.1/1.4
V
ICL
NPN Switch Current
Limit
6.5
5.0
9.5
A
V
=
VSTH
Synchronization
Threshold Voltage
Synchronization
Pin Current
FSYNC 200 kHz
0.75
0.625/0.40
0.875/1.00
=
=
VCOMP 1V, VIN 5V
=
ISYNC
VSHTH
ISH
VIN 5V
100
1.6
40
200
µA
V
=
=
VCOMP 1V, VSYNC VSTH
=
ON /OFF Pin (Pin 1) VCOMP 1V
Threshold Voltage (Note 10)
ON /OFF Pin (Pin 1) VCOMP 1V
1.0/0.8
15/10
2.2/2.4
65/75
=
µA
=
Current
VSH VSHTH
θJA
Thermal Resistance
T Package, Junction to Ambient
(Note 11)
65
θJA
T Package, Junction to Ambient
(Note 12)
45
θJC
θJA
T Package, Junction to Case
S Package, Junction to Ambient
(Note 13)
2
56
˚C/W
θJA
θJA
θJC
S Package, Junction to Ambient
(Note 14)
35
26
2
S Package, Junction to Ambient
(Note 15)
S Package, Junction to Case
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. These ratings apply when the current is limited to less than 1.2 mA
for pins 1, 2, 3, and 6. Operating ratings indicate conditions for which the device is intended to be functional, but device parameter specifications may not be guar-
anteed under these conditions. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Note that switch current and output current are not identical in a step-up regulator. Output current cannot be internally limited when the LM2588 is used as
a step-up regulator. To prevent damage to the switch, the output current must be externally limited to 5A. However, output current is internally limited when the
LM2588 is used as a flyback regulator (see the Application Hints section for more information).
Note 3: The junction temperature of the device (T ) is a function of the ambient temperature (T ), the junction-to-ambient thermal resistance (θ ), and the power
JA
J
A
dissipation of the device (P ). A thermal shutdown will occur if the temperature exceeds the maximum junction temperature of the device: P x θ + T
JA A(MAX)
≥ T -
J
D
D
(MAX). For a safe thermal design, check that the maximum power dissipated by the device is less than: P ≤ [T
− T ]/θ . When calculating the maximum
A(MAX) JA
D
J(MAX)
allowable power dissipation, derate the maximum junction temperature — this ensures a margin of safety in the thermal design.
Note 4: External components such as the diode, inductor, input and output capacitors can affect switching regulator performance. When the LM2588 is used as
shown in Figure 1 and Figure 2, system performance will be as specified by the system parameters.
Note 5: All room temperature limits are 100% production tested, and all limits at temperature extremes are guaranteed via correlation using standard Statistical Qual-
ity Control (SQC) methods.
Note 6: A 1.0 MΩ resistor is connected to the compensation pin (which is the error amplifier output) to ensure accuracy in measuring A
.
VOL
Note 7: To measure this parameter, the feedback voltage is set to a low value, depending on the output version of the device, to force the error amplifier output high
and the switch on.
Note 8: To measure this parameter, the feedback voltage is set to a high value, depending on the output version of the device, to force the error amplifier output low
and the switch off.
Note 9: To measure the worst-case error amplifier output current, the LM2588 is tested with the feedback voltage set to its low value (specified in (Note 7)) and at
its high value (specified in (Note 8)).
Note 10: When testing the minimum value, do not sink current from this pin — isolate it with a diode. If current is drawn from this pin, the frequency adjust circuit will
begin operation (see Figure 41).
Note 11: Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with 1
⁄2
inch leads in a socket, or on a PC
board with minimum copper area.
Note 12: Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with 1⁄2 inch leads soldered to a PC board
containing approximately 4 square inches of (1 oz.) copper area surrounding the leads.
Note 13: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board area of 0.136 square inches (the same size as the
TO-263 package) of 1 oz. (0.0014 in. thick) copper.
Note 14: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board area of 0.4896 square inches (3.6 times the area
of the TO-263 package) of 1 oz. (0.0014 in. thick) copper.
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6
All Output Voltage Versions
Electrical Characteristics (Note 5) (Continued)
Note 15: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board copper area of 1.0064 square inches (7.4 times the
area of the TO-263 package) of 1 oz. (0.0014 in. thick) copper. Additional copper area will reduce thermal resistance further. See the thermal model in Switchers Made
Simple® software.
Typical Performance Characteristics
Supply Current
vs Temperature
Reference Voltage
vs Temperature
∆Reference Voltage
vs Supply Voltage
DS012420-2
DS012420-3
DS012420-4
Supply Current
vs Switch Current
Current Limit
vs Temperature
Feedback Pin Bias
Current vs Temperature
DS012420-5
DS012420-6
DS012420-7
Switch Saturation
Voltage vs Temperature
Switch Transconductance
vs Temperature
Oscillator Frequency
vs Temperature
DS012420-8
DS012420-9
DS012420-10
7
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Typical Performance Characteristics (Continued)
Error Amp Transconductance
vs Temperature
Error Amp Voltage
Gain vs Temperature
Short Circuit Frequency
vs Temperature
DS012420-11
DS012420-12
DS012420-13
Shutdown Supply Current
vs Temperature
ON /OFF Pin Current
vs Voltage
Oscillator Frequency
vs Resistance
DS012420-14
DS012420-15
DS012420-16
Connection Diagrams
Bent, Staggered Leads
7-Lead TO-220 (T)
Top View
Bent, Staggered Leads
7-Lead TO-220 (T)
Side View
DS012420-18
DS012420-17
Order Number LM2588T-3.3, LM2588T-5.0,
LM2588T-12 or LM2588T-ADJ
See NS Package Number TA07B
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8
Connection Diagrams (Continued)
7-Lead TO-263 (S)
Top View
7-Lead TO-263 (S)
Side View
DS012420-20
DS012420-19
Order Number LM2588S-3.3, LM2588S-5.0,
LM2588S-12 or LM2588S-ADJ
Tape and Reel Order Number LM2588SX-3.3,
LM2588SX-5.0, LM2588SX-12 or LM2588SX-ADJ
See NS Package Number TS7B
Test Circuits
DS012420-21
C
C
— 100 µF, 25V Aluminum Electrolytic
— 0.1 µF Ceramic
IN1
IN2
T — 22 µH, 1:1 Schott #67141450
D — 1N5820
C
C
R
— 680 µF, 16V Aluminum Electrolytic
— 0.47 µF Ceramic
— 2k
OUT
C
C
FIGURE 1. LM2588-3.3 and LM2588-5.0
9
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Test Circuits (Continued)
DS012420-22
C
C
— 100 µF, 25V Aluminum Electrolytic
— 0.1 µF Ceramic
IN1
IN2
L — 15 µH, Renco #RL-5472-5
D — 1N5820
C
C
R
— 680 µF, 16V Aluminum Electrolytic
OUT
C
C
— 0.47 µF Ceramic
— 2k
=
For 12V Devices: R1 Short (0Ω) and
=
R2 Open
For ADJ Devices: R1 48.75k, 0.1% and
R2 5.62k, 0.1%
=
±
=
±
FIGURE 2. LM2588-12 and LM2588-ADJ
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10
Block Diagram
DS012420-23
For Fixed Versions
=
=
3.3V, R1 3.4k, R2 2k
=
=
5.0V, R1 6.15k, R2 2k
=
=
12V, R1 8.73k, R2 1k
For Adj. Version
=
=
R1 Short (0Ω), R2 Open
FIGURE 3.
Flyback Regulator Operation
The LM2588 is ideally suited for use in the flyback regulator
topology. The flyback regulator can produce a single output
voltage, such as the one shown in Figure 4, or multiple out-
put voltages. In Figure 4, the flyback regulator generates an
output voltage that is inside the range of the input voltage.
This feature is unique to flyback regulators and cannot be
duplicated with buck or boost regulators.
lapses, reversing the voltage polarity of the primary and sec-
ondary windings. Now rectifier D1 is forward biased and
current flows through it, releasing the energy stored in the
transformer. This produces voltage at the output.
The output voltage is controlled by modulating the peak
switch current. This is done by feeding back a portion of the
output voltage to the error amp, which amplifies the differ-
ence between the feedback voltage and a 1.230V reference.
The error amp output voltage is compared to a ramp voltage
proportional to the switch current (i.e., inductor current dur-
ing the switch on time). The comparator terminates the
switch on time when the two voltages are equal, thereby
controlling the peak switch current to maintain a constant
output voltage.
The operation of a flyback regulator is as follows (refer to
Figure 4): when the switch is on, current flows through the
primary winding of the transformer, T1, storing energy in the
magnetic field of the transformer. Note that the primary and
secondary windings are out of phase, so no current flows
through the secondary when current flows through the pri-
mary. When the switch turns off, the magnetic field col-
11
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Flyback Regulator Operation (Continued)
DS012420-24
As shown in Figure 4, the LM2588 can be used as a flyback regulator by using a minimum number of external components. The switching waveforms of this
regulator are shown in Figure 5. Typical Performance Characteristics observed during the operation of this circuit are shown in Figure 6.
FIGURE 4. 12V Flyback Regulator Design Example
Typical Performance Characteristics
DS012420-60
DS012420-61
A: Switch Voltage, 10V/div
B: Switch Current, 5A/div
C: Output Rectifier Current, 5A/div
D: Output Ripple Voltage, 100 mV/div
AC-Coupled
FIGURE 6. VOUT Response to Load Current Step
FIGURE 5. Switching Waveforms
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12
Typical Flyback Regulator Applications
Figure 7 through 12 show six typical flyback applications,
varying from single output to triple output. Each drawing con-
tains the part number(s) and manufacturer(s) for every com-
ponent except the transformer. For the transformer part
numbers and manufacturers’ names, see the table in Figure
13.
For
applications
with
different
output
voltages — requiring the LM2588-ADJ — or different output
configurations that do not match the standard configurations,
refer to the Switchers Made Simple software.
™
DS012420-25
FIGURE 7. Single-Output Flyback Regulator
DS012420-26
FIGURE 8. Single-Output Flyback Regulator
13
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Typical Flyback Regulator Applications (Continued)
DS012420-27
FIGURE 9. Single-Output Flyback Regulator
DS012420-28
FIGURE 10. Dual-Output Flyback Regulator
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14
Typical Flyback Regulator Applications (Continued)
DS012420-29
FIGURE 11. Dual-Output Flyback Regulator
DS012420-30
FIGURE 12. Triple-Output Flyback Regulator
15
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Typical Flyback Regulator Applications (Continued)
Transformer Selection (T)
Figure 13 lists the standard transformers available for flyback regulator applications. Included in the table are the turns ratio(s) for
each transformer, as well as the output voltages, input voltage ranges, and the maximum load currents for each circuit.
Applications
Transformers
VIN
Figure 7
T1
Figure 8
T1
Figure 9
T1
Figure 10
T2
Figure 11
T3
Figure 12
T4
4V–6V
3.3V
1.8A
1
4V–6V
5V
8V–16V
12V
4V–6V
12V
18V–36V
12V
18V–36V
5V
VOUT1
IOUT1 (Max)
N1
1.4A
1
1.2A
1
0.3A
2.5
1A
2.5A
0.35
0.8
VOUT2
−12V
0.3A
2.5
−12V
1A
12V
IOUT2 (Max)
N2
0.5A
0.8
0.8
VOUT3
−12V
0.5A
0.8
IOUT3 (Max)
N3
FIGURE 13. Transformer Selection Table
Manufacturers’ Part Numbers
Transformer
Type
Coilcraft
(Note 16)
Q4434-B
Q4337-B
Q4343-B
Q4344-B
Coilcraft (Note 16)
Pulse (Note 17)
Surface Mount
PE-68411
Renco
Schott
Surface Mount
(Note 18)
RL-5530
RL-5531
RL-5534
RL-5535
(Note 19)
67141450
67140860
67140920
67140930
T1
T2
T3
T4
Q4435-B
Q4436-B
—
PE-68412
PE-68421
—
PE-68422
Note 16: Coilcraft Inc.,: Phone: (800) 322-2645
1102 Silver Lake Road, Cary, IL 60013: Fax: (708) 639-1469
European Headquarters, 21 Napier Place: Phone: +44 1236 730 595
Wardpark North, Cumbernauld, Scotland G68 0LL: Fax: +44 1236 730 627
Note 17: Pulse Engineering Inc.,: Phone: (619) 674-8100
12220 World Trade Drive, San Diego, CA 92128: Fax: (619) 674-8262
European Headquarters, Dunmore Road: Phone: +353 93 24 107
Tuam, Co. Galway, Ireland: Fax: +353 93 24 459
Note 18: Renco Electronics Inc.,: Phone: (800) 645-5828
60 Jeffryn Blvd. East, Deer Park, NY 11729: Fax: (516) 586-5562
Note 19: Schott Corp.,: Phone: (612) 475-1173
1000 Parkers Lane Road, Wayzata, MN 55391: Fax: (612) 475-1786
FIGURE 14. Transformer Manufacturer Guide
Transformer Footprints
Figure 15 through 32 show the footprints of each transformer, listed in Figure 14.
T1
T2
DS012420-31
Top View
DS012420-32
FIGURE 15. Coilcraft Q4434-B
Top View
FIGURE 16. Coilcraft Q4337-B
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16
Typical Flyback Regulator
Applications (Continued)
T1
T3
DS012420-37
DS012420-33
Top View
Top View
FIGURE 21. Pulse PE-68411
(Surface Mount)
FIGURE 17. Coilcraft Q4343-B
T4
T2
DS012420-38
DS012420-34
Top View
Top View
FIGURE 22. Pulse PE-68412
(Surface Mount)
FIGURE 18. Coilcraft Q4344-B
T1
T3
DS012420-39
DS012420-35
Top View
Top View
FIGURE 23. Pulse PE-68421
(Surface Mount)
FIGURE 19. Coilcraft Q4435-B
(Surface Mount)
T4
T2
DS012420-36
Top View
FIGURE 20. Coilcraft Q4436-B
(Surface Mount)
DS012420-40
Top View
FIGURE 24. Pulse PE-68422
(Surface Mount)
17
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Typical Flyback Regulator
Applications (Continued)
T4
T1
DS012420-44
DS012420-41
Top View
Top View
FIGURE 28. Renco RL-5535
FIGURE 25. Renco RL-5530
T2
T1
DS012420-45
DS012420-42
Top View
Top View
FIGURE 29. Schott 67141450
FIGURE 26. Renco RL-5531
T2
T3
DS012420-46
DS012420-43
Top View
Top View
FIGURE 30. Schott 67140860
FIGURE 27. Renco RL-5534
T3
DS012420-47
Top View
FIGURE 31. Schott 67140920
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18
Typical Flyback Regulator Applications (Continued)
T4
DS012420-48
Top View
FIGURE 32. Schott 67140930
19
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Step-Up (Boost) Regulator Operation
Figure 33 shows the LM2588 used as a step-up (boost)
regulator. This is a switching regulator that produces an out-
put voltage greater than the input supply voltage.
off, the lower end of the inductor flies above VIN, discharging
its current through diode (D) into the output capacitor (COUT
)
at a rate of (VOUT − VIN)/L. Thus, energy stored in the induc-
tor during the switch on time is transferred to the output dur-
ing the switch off time. The output voltage is controlled by
adjusting the peak switch current, as described in the flyback
regulator section.
A brief explanation of how the LM2588 Boost Regulator
works is as follows (refer to Figure 33). When the NPN
switch turns on, the inductor current ramps up at the rate of
V
IN/L, storing energy in the inductor. When the switch turns
DS012420-49
FIGURE 33. 12V Boost Regulator
By adding a small number of external components (as shown in Figure 33), the LM2588 can be used to produce a regulated out-
put voltage that is greater than the applied input voltage. The switching waveforms observed during the operation of this circuit
are shown in Figure 34. Typical performance of this regulator is shown in Figure 35.
Typical Performance Characteristics
DS012420-63
DS012420-62
A: Switch Voltage,10V/div
B: Switch Current, 5A/div
C: Inductor Current, 5A/div
D: Output Ripple Voltage,
100 mV/div, AC-Coupled
FIGURE 35. VOUT Response to Load Current Step
FIGURE 34. Switching Waveforms
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20
Typical Boost Regulator Applications
Figure 36 and 38 through 40 show four typical boost
applications — one fixed and three using the adjustable ver-
sion of the LM2588. Each drawing contains the part num-
ber(s) and manufacturer(s) for every component. For the
fixed 12V output application, the part numbers and manufac-
turers’ names for the inductor are listed in a table in Figure
37. For applications with different output voltages, refer to
the Switchers Made Simplesoftware.
DS012420-50
FIGURE 36. +5V to +12V Boost Regulator
Figure 37 contains a table of standard inductors, by part number and corresponding manufacturer, for the fixed output regulator
of Figure 36.
Coilcraft (Note 20)
R4793-A
Pulse (Note 21)
Renco (Note 22)
Schott (Note 23)
PE-53900
RL-5472-5
67146520
Note 20: Coilcraft Inc.,: Phone: (800) 322-2645
1102 Silver Lake Road, Cary, IL 60013: Fax: (708) 639-1469
European Headquarters, 21 Napier Place: Phone: +44 1236 730 595
Wardpark North, Cumbernauld, Scotland G68 0LL: Fax: +44 1236 730 627
Note 21: Pulse Engineering Inc.,: Phone: (619) 674-8100
12220 World Trade Drive, San Diego, CA 92128: Fax: (619) 674-8262
European Headquarters, Dunmore Road: Phone: +353 93 24 107
Tuam, Co. Galway, Ireland: Fax: +353 93 24 459
Note 22: Renco Electronics Inc.,: Phone: (800) 645-5828
60 Jeffryn Blvd. East, Deer Park, NY 11729: Fax: (516) 586-5562
Note 23: Schott Corp.,: Phone: (612) 475-1173
1000 Parkers Lane Road, Wayzata, MN 55391: Fax: (612) 475-1786
FIGURE 37. Inductor Selection Table
21
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Typical Boost Regulator Applications (Continued)
DS012420-51
FIGURE 38. +12V to +24V Boost Regulator
DS012420-52
FIGURE 39. +24V to +36V Boost Regulator
DS012420-53
*
The LM2588 will require a heat sink in these applications. The size of the heat sink will depend on the maximum ambient temperature. To calculate the thermal
resistance of the IC and the size of the heat sink needed, see the “Heat Sink/Thermal Considerations” section in the Application Hints.
FIGURE 40. +24V to +48V Boost Regulator
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22
Application Hints
LM2588 SPECIAL FEATURES
DS012420-55
FIGURE 43. Frequency Synchronization
FREQUENCY SYNCHRONIZATION
Another feature of the LM2588 is the ability to synchronize
the switching frequency to an external source, using the
sync pin (pin 6). This feature allows the user to parallel mul-
tiple devices to deliver more output power.
A negative falling pulse applied to the sync pin will synchro-
nize the LM2588 to an external oscillator (see Figure 43 and
44).
DS012420-54
FIGURE 41. Shutdown Operation
SHUTDOWN CONTROL
Use of this feature enables the LM2588 to be synchronized
to an external oscillator, such as a system clock. This opera-
tion allows multiple power supplies to operate at the same
frequency, thus eliminating frequency-related noise
problems.
A feature of the LM2588 is its ability to be shut down using
the ON /OFF pin (pin 1). This feature conserves input power
by turning off the device when it is not in use. For proper op-
eration, an isolation diode is required (as shown in Figure
41).
The device will shut down when 3V or greater is applied on
the ON /OFF pin, sourcing current into pin 1. In shut down
mode, the device will draw typically 56 µA of supply current
(16 µA to VIN and 40 µA to the ON /OFF pin). To turn the de-
vice back on, leave pin 1 floating, using an (isolation) diode,
as shown in Figure 41 (for normal operation, do not source
or sink current to or from this pin — see the next section).
FREQUENCY ADJUSTMENT
The switching frequency of the LM2588 can be adjusted with
the use of an external resistor. This feature allows the user to
optimize the size of the magnetics and the output capaci-
tor(s) by tailoring the operating frequency. A resistor con-
nected from pin 1 (the Freq. Adj. pin) to ground will set the
switching frequency from 100 kHz to 200 kHz (maximum).
As shown in Figure 41, the pin can be used to adjust the fre-
quency while still providing the shut down function. A curve in
the Performance Characteristics Section graphs the resistor
value to the corresponding switching frequency. The table in
Figure 42 shows resistor values corresponding to commonly
used frequencies.
DS012420-64
FIGURE 44. Waveforms of a Synchronized
12V Boost Regulator
The scope photo in Figure 44 shows a LM2588 12V Boost
Regulator synchronized to a 200 kHz signal. There is a 700
ns delay between the falling edge of the sync signal and the
turning on of the switch.
PROGRAMMING OUTPUT VOLTAGE
(SELECTING R1 AND R2)
However, changing the LM2588’s operating frequency from
its nominal value of 100 kHz will change the magnetics se-
lection and compensation component values.
Referring to the adjustable regulator in Figure 45, the output
voltage is programmed by the resistors R1 and R2 by the fol-
lowing formula:
=
=
where VREF 1.23V
VOUT VREF (1 + R1/R2)
RSET(kΩ)
Open
200
Frequency (kHz)
Resistors R1 and R2 divide the output voltage down so that
it can be compared with the 1.23V internal reference. With
R2 between 1k and 5k, R1 is:
100
125
150
175
200
47
=
=
where VREF 1.23V
R1 R2 (VOUT/VREF − 1)
33
For best temperature coefficient and stability with time, use
1% metal film resistors.
22
FIGURE 42. Frequency Setting Resistor Guide
SHORT CIRCUIT CONDITION
Due to the inherent nature of boost regulators, when the out-
put is shorted (see Figure 45 ), current flows directly from the
input, through the inductor and the diode, to the output, by-
passing the switch. The current limit of the switch does not
limit the output current for the entire circuit. To protect the
23
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the main output. When the output voltage drops to 80% of its
nominal value, the frequency will drop to 25 kHz. With a
lower frequency, off times are larger. With the longer off
times, the transformer can release all of its stored energy be-
fore the switch turns back on. Hence, the switch turns on ini-
tially with zero current at its collector. In this condition, the
switch current limit will limit the peak current, saving the
device.
Application Hints (Continued)
load and prevent damage to the switch, the current must be
externally limited, either by the input supply or at the output
with an external current limit circuit. The external limit should
be set to the maximum switch current of the device, which is
5A.
In a flyback regulator application (Figure 46 ), using the stan-
dard transformers, the LM2588 will survive a short circuit to
DS012420-56
FIGURE 45. Boost Regulator
DS012420-57
FIGURE 46. Flyback Regulator
FLYBACK REGULATOR INPUT CAPACITORS
capacitor. The storage capacitor will also attenuate noise
which may interfere with other circuits connected to the
same input supply voltage.
A flyback regulator draws discontinuous pulses of current
from the input supply. Therefore, there are two input capaci-
tors needed in a flyback regulator — one for energy storage
and one for filtering (see Figure 46). Both are required due to
the inherent operation of a flyback regulator. To keep a
stable or constant voltage supply to the LM2588, a storage
capacitor (≥100 µF) is required. If the input source is a reciti-
fied DC supply and/or the application has a wide tempera-
ture range, the required rms current rating of the capacitor
might be very large. This means a larger value of capaci-
tance or a higher voltage rating will be needed for the input
In addition, a small bypass capacitor is required due to the
noise generated by the input current pulses. To eliminate the
noise, insert a 1.0 µF ceramic capacitor between VIN and
ground as close as possible to the device.
www.national.com
24
Application Hints (Continued)
SWITCH VOLTAGE LIMITS
In a flyback regulator, the maximum steady-state voltage ap-
pearing at the switch, when it is off, is set by the transformer
turns ratio, N, the output voltage, VOUT, and the maximum in-
put voltage, VIN (Max):
=
VSW(OFF) VIN (Max) + (VOUT +VF)/N
where VF is the forward biased voltage of the output diode,
and is typically 0.5V for Schottky diodes and 0.8V for
ultra-fast recovery diodes. In certain circuits, there exists a
voltage spike, VLL, superimposed on top of the steady-state
voltage (see Figure 5, waveform A). Usually, this voltage
spike is caused by the transformer leakage inductance
and/or the output rectifier recovery time. To “clamp” the volt-
age at the switch from exceeding its maximum value, a tran-
sient suppressor in series with a diode is inserted across the
transformer primary (as shown in the circuit in Figure 4 and
other flyback regulator circuits throughout the datasheet).
The schematic in Figure 46 shows another method of clamp-
ing the switch voltage. A single voltage transient suppressor
(the SA51A) is inserted at the switch pin. This method
clamps the total voltage across the switch, not just the volt-
age across the primary.
DS012420-58
FIGURE 47. Input Line Filter
OUTPUT VOLTAGE LIMITATIONS
The maximum output voltage of a boost regulator is the
maximum switch voltage minus a diode drop. In a flyback
regulator, the maximum output voltage is determined by the
turns ratio, N, and the duty cycle, D, by the equation:
VOUT ≈ N x VIN x D/(1 − D)
If poor circuit layout techniques are used (see the “Circuit
Layout Guideline” section), negative voltage transients may
appear on the Switch pin (pin 5). Applying a negative voltage
(with respect to the IC’s ground) to any monolithic IC pin
causes erratic and unpredictable operation of that IC. This
holds true for the LM2588 IC as well. When used in a flyback
regulator, the voltage at the Switch pin (pin 5) can go nega-
tive when the switch turns on. The “ringing” voltage at the
switch pin is caused by the output diode capacitance and the
transformer leakage inductance forming a resonant circuit at
the secondary(ies). The resonant circuit generates the “ring-
ing” voltage, which gets reflected back through the trans-
former to the switch pin. There are two common methods to
avoid this problem. One is to add an RC snubber around the
output rectifier(s), as in Figure 46. The values of the resistor
and the capacitor must be chosen so that the voltage at the
Switch pin does not drop below −0.4V. The resistor may
range in value between 10Ω and 1 kΩ, and the capacitor will
vary from 0.001 µF to 0.1 µF. Adding a snubber will (slightly)
reduce the efficiency of the overall circuit.
The duty cycle of a flyback regulator is determined by the fol-
lowing equation:
Theoretically, the maximum output voltage can be as large
as desired — just keep increasing the turns ratio of the trans-
former. However, there exists some physical limitations that
prevent the turns ratio, and thus the output voltage, from in-
creasing to infinity. The physical limitations are capacitances
and inductances in the LM2588 switch, the output diode(s),
and the transformer — such as reverse recovery time of the
output diode (mentioned above).
NOISY INPUT LINE CONDITION
A small, low-pass RC filter should be used at the input pin of
the LM2588 if the input voltage has an unusually large
amount of transient noise, such as with an input switch that
bounces. The circuit in Figure 47 demonstrates the layout of
the filter, with the capacitor placed from the input pin to
ground and the resistor placed between the input supply and
the input pin. Note that the values of RIN and CIN shown in
the schematic are good enough for most applications, but
some readjusting might be required for a particular applica-
tion. If efficiency is a major concern, replace the resistor with
a small inductor (say 10 µH and rated at 200 mA).
The other method to reduce or eliminate the “ringing” is to in-
sert a Schottky diode clamp between pins 5 and 4 (ground),
also shown in Figure 46. This prevents the voltage at pin 5
from dropping below −0.4V. The reverse voltage rating of the
diode must be greater than the switch off voltage.
STABILITY
All current-mode controlled regulators can suffer from an in-
stability, known as subharmonic oscillation, if they operate
with a duty cycle above 50%. To eliminate subharmonic os-
cillations, a minimum value of inductance is required to en-
sure stability for all boost and flyback regulators. The mini-
mum inductance is given by:
where VSAT is the switch saturation voltage and can be
found in the Characteristic Curves.
25
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Application Hints (Continued)
DS012420-59
FIGURE 48. Circuit Board Layout
∑
CIRCUIT LAYOUT GUIDELINES
is the maximum load current (and ILOAD is the sum of the
maximum load currents for multiple-output flyback regula-
tors). The duty cycle is given by:
As in any switching regulator, layout is very important. Rap-
idly switching currents associated with wiring inductance
generate voltage transients which can cause problems. For
minimal inductance and ground loops, keep the length of the
leads and traces as short as possible. Use single point
grounding or ground plane construction for best results.
Separate the signal grounds from the power grounds (as in-
dicated in Figure 48). When using the Adjustable version,
physically locate the programming resistors as near the
regulator IC as possible, to keep the sensitive feedback wir-
ing short.
Boost:
where VF is the forward biased voltage of the diode and is
typically 0.5V for Schottky diodes and 0.8V for fast recovery
diodes. VSAT is the switch saturation voltage and can be
found in the Characteristic Curves.
HEAT SINK/THERMAL CONSIDERATIONS
In many cases, a heat sink is not required to keep the
LM2588 junction temperature within the allowed operating
temperature range. For each application, to determine
whether or not a heat sink will be required, the following must
be identified:
When no heat sink is used, the junction temperature rise is:
=
∆TJ PD • θJA
.
Adding the junction temperature rise to the maximum ambi-
ent temperature gives the actual operating junction tempera-
ture:
1) Maximum ambient temperature (in the application).
2) Maximum regulator power dissipation (in the application).
=
TJ ∆TJ + TA.
3) Maximum allowed junction temperature (125˚C for the
LM2588). For a safe, conservative design, a temperature ap-
proximately 15˚C cooler than the maximum junction tem-
perature should be selected (110˚C).
If the operating junction temperature exceeds the maximum
junction temperatue in item 3 above, then a heat sink is re-
quired. When using a heat sink, the junction temperature rise
can be determined by the following:
4) LM2588 package thermal resistances θJA and θJC (given
in the Electrical Characteristics).
=
∆TJ PD • (θJC + θInterface + θHeat Sink
)
Again, the operating junction temperature will be:
Total power dissipated (PD) by the LM2588 can be estimated
as follows:
=
TJ ∆TJ + TA
Boost:
As before, if the maximum junction temperature is exceeded,
a larger heat sink is required (one that has a lower thermal
resistance).
Included in the Switchers Made Simple design software is a
more precise (non-linear) thermal model that can be used to
determine junction temperature with different input-output
parameters or different component values. It can also calcu-
late the heat sink thermal resistance required to maintain the
regulator junction temperature below the maximum operat-
ing temperature.
VIN is the minimum input voltage, VOUT is the output voltage,
N is the transformer turns ratio, D is the duty cycle, and ILOAD
www.national.com
26
on a (31⁄
") diskette for IBM compatible computers from a
2
Application Hints (Continued)
National Semiconductor sales office in your area or the Na-
tional Semiconductor Customer Response Center
(1-800-272-9959).
To further simplify the flyback regulator design procedure,
National Semiconductor is making available computer de-
sign software Switchers Made Simple. Software is available
27
www.national.com
Physical Dimensions inches (millimeters) unless otherwise noted
Order Number LM2588T-3.3, LM2588T-5.0,
LM2588T-12 or LM2588T-ADJ
NS Package Number TA07B
www.national.com
28
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number LM2588S-3.3, LM2588S-5.0,
LM2588S-12 or LM2588S-ADJ
Tape and Reel Order Number LM2588SX-3.3,
LM2588SX-5.0, LM2588SX-12 or LM2588SX-ADJ
NS Package Number TS7B
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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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Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
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Products > Analog - Regulators > Simple Switchers > LM2588
LM2588 Product Folder
SIMPLE SWITCHER 5A Flyback Regulator with Shutdown
Generic P/N 2588
General
Description
Package
& Models
Samples
& Pricing
Design
Tools
Application
Notes
Features
Datasheet
WEBENCH Live Simulation!
Parametric Table
Multiple Output Capability
On/Off Pin
Yes
LM2588 Webench™ Custom
Design/Analyze/Build It
Yes
Error Flag
No
V in Lower
V in Upper
Input Voltage, min (Volt)
Input Voltage, max (Volt)
Output Current, max
Output Voltage (Volt)
Adjustable Output Voltage
Switching Frequency (Hz)
4
4.0 <=
V out
I out
<=
<= 40.0
<= 300.0
<= 5.00
<= 100
4.5
5.5
V
V
40
1.2 <=
12.0
1.00
5000 mA
12, 3.30, 5
No, Yes
200000
Yes
V
A
Ambient Temperature
30
°C
Adjustable Switching Frequency
Sync Pin
Yes
Create This Design
Efficiency (%)
Flyback
90, 75, 80
Yes
What is Webench?
Step-up
Yes
-
Datasheet
Size in
Kbytes
Title
Date
Receive via
Email
Download
View Online
29-
Jun-
99
Receive via
Email
LM2588 SIMPLE SWITCHER 5A Flyback Regulator with
Shutdown
786
Kbytes
View Online Download
LM2588 SIMPLE SWITCHER 5A Flyback Regulator with
Shutdown (JAPANESE)
922
Kbytes
View Online Download
Receive via
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Package Availability, Models, Samples & Pricing
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Samples
TO 263
TO 263
TO 263
TO 263
LM2588S-12
LM2588S-3.3
LM2588S-5.0
LM2588S-ADJ
-12 P+
Samples
rail
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45
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LM2588S
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-3.3 P+
rail
of
45
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LM2588S
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Samples
24 Hour
-5.0 P+
rail
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45
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LM2588S
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-ADJ P+
reel
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500
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LM2588S
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TO 263
TO 263
TO 263
TO 263
MSL
MSL
MSL
MSL
LM2588SX-12
LM2588SX-3.3
LM2588SX-5.0
LM2588SX-ADJ
7
7
7
7
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
1K+ $4.2700
1K+ $4.2700
1K+ $4.2700
1K+ $4.2700
-12 P+
reel
of
500
[logo]¢U¢Z¢2¢T
LM2588S
Full
production
-3.3 P+
reel
of
500
[logo]¢U¢Z¢2¢T
LM2588S
Full
production
-5.0 P+
reel
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500
[logo]¢U¢Z¢2¢T
LM2588S
Full
production
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Samples
-ADJ P+
gel pak
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N/A
LM2588-12
MDC
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Die
-
-
-
gel pak
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N/A
LM2588-5.0
MDC
Full
production
Samples
Samples
Die
Die
gel pak
of
N/A
LM2588-ADJ
MDC
Full
production
wafer
jar
of
LM2588-12
MWC
Full
production
Wafer
Wafer
N/A
N/A
N/A
N/A
-
-
N/A
wafer
jar
of
LM2588-ADJ
MWC
Full
production
N/A
General Description
The LM2588 series of regulators are monolithic integrated circuits specifically designed for flyback, step-up
(boost), and forward converter applications. The device is available in 4 different output voltage versions:
3.3V, 5.0V, 12V, and adjustable.
Requiring a minimum number of external components, these regulators are cost effective, and simple to use.
Included in the datasheet are typical circuits of boost and flyback regulators. Also listed are selector guides
for diodes and capacitors and a family of standard inductors and flyback transformers designed to work with
these switching regulators.
The power switch is a 5.0A NPN device that can stand-off 65V. Protecting the power switch are current and
thermal limiting circuits, and an undervoltage lockout circuit. This IC contains an adjustable frequency
oscillator that can be programmed up to 200 kHz. The oscillator can also be synchronized with other devices,
so that multiple devices can operate at the same switching frequency.
Other features include 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 and cycle-by-cycle current limiting. The
device also has a shutdown pin, so that it can be turned off externally. An output voltage tolerance of ±4%,
within specified input voltages and output load conditions, is guaranteed for the power supply system.
Features
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Requires few external components
Family of standard inductors and transformers
NPN output switches 5.0A, can stand off 65V
Wide input voltage range: 4V to 40V
Adjustable switching frequency: 100 kHz to 200 kHz
External shutdown capability
Draws less than 60 µA when shut down
Frequency synchronization
Current-mode operation for improved transient response, line regulation, and current limit
Internal soft-start function reduces in-rush current during start-up
Output transistor protected by current limit, under voltage lockout, and thermal shutdown
System output voltage tolerance of ±4% max over line and load conditions
Applications
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Flyback regulator
Forward converter
Multiple-output regulator
Simple boost regulator
Design Tools
Title
Size in Kbytes Date
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Email
Download
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SimpleSwitcher® DC-DC
Converters Design Software
12-Jun-
2002
View
10 Kbytes
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Application Notes
Title
Size in Kbytes Date
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AN-1082: Application Note 1082
Adjust or Synchronize LM2586/88 25 Kbytes
Switching Frequency
View Online Download Receive via Email
View Online Download Receive via Email
4-Feb-98
5-Jan-97
AN-1061: AN-1061 Power
Conversion in Line-Powered
Equipment
142 Kbytes
If you have trouble printing or viewing PDF file(s), see Printing Problems.
[Information as of 5-Aug-2002]
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