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PDF LB03 Data sheet ( Hoja de datos )
| Número de pieza | LB03 | |
| Descripción | SIMPLE SWITCHER 3A Step-Down Voltage Regulator | |
| Fabricantes | National | |
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June 1999
LM2576/LM2576HV Series
SIMPLE SWITCHER® 3A Step-Down Voltage Regulator
General Description
The LM2576 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving 3A load with
excellent line and load regulation. These devices are avail-
able in fixed output voltages of 3.3V, 5V, 12V, 15V, and an
adjustable output version.
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation and a fixed-frequency oscillator.
The LM2576 series offers a high-efficiency replacement for
popular three-terminal linear regulators. It substantially re-
duces the size of the heat sink, and in some cases no heat
sink is required.
A standard series of inductors optimized for use with the
LM2576 are available from several different manufacturers.
This feature greatly simplifies the design of switch-mode
power supplies.
Other features include a guaranteed ±4% tolerance on out-
put voltage within specified input voltages and output load
conditions, and ±10% on the oscillator frequency. External
shutdown is included, featuring 50 µA (typical) standby cur-
rent. The output switch includes cycle-by-cycle current limit-
ing, as well as thermal shutdown for full protection under
fault conditions.
Features
n 3.3V, 5V, 12V, 15V, and adjustable output versions
n Adjustable version output voltage range,
1.23V to 37V (57V for HV version) ±4% max over
line and load conditions
n Guaranteed 3A output current
n Wide input voltage range, 40V up to 60V for
HV version
n Requires only 4 external components
n 52 kHz fixed frequency internal oscillator
n TTL shutdown capability, low power standby mode
n High efficiency
n Uses readily available standard inductors
n Thermal shutdown and current limit protection
n P+ Product Enhancement tested
Applications
n Simple high-efficiency step-down (buck) regulator
n Efficient pre-regulator for linear regulators
n On-card switching regulators
n Positive to negative converter (Buck-Boost)
Typical Application (Fixed Output Voltage Versions)
FIGURE 1.
DS011476-1
SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS011476
www.national.com
1 page  
LM2576-ADJ, LM2576HV-ADJ
Electrical Characteristics (Continued)
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Temperature
Range.
Symbol
Parameter
Conditions
LM2576-ADJ
LM2576HV-ADJ
Units
(Limits)
Typ Limit
(Note 2)
SYSTEM PARAMETERS (Note 3) Test Circuit Figure 2
VOUT
VOUT
η
Feedback Voltage
LM2576
Feedback Voltage
LM2576HV
Efficiency
0.5A ≤ ILOAD ≤ 3A,
8V ≤ VIN ≤ 40V
VOUT = 5V, Circuit of Figure 2
0.5A ≤ ILOAD ≤ 3A,
8V ≤ VIN ≤ 60V
VOUT = 5V, Circuit of Figure 2
VIN = 12V, ILOAD = 3A, VOUT = 5V
1.230
1.230
77
1.193/1.180
1.267/1.280
1.193/1.180
1.273/1.286
V
V(Min)
V(Max)
V
V(Min)
V(Max)
%
All Output Voltage Versions
Electrical Characteristics
Specifications with standard type face are for TJ = 25˚C, and those with boldface type apply over full Operating Temperature
VRIaNng=e3. 0UVnlfeosrsthoeth1e5rwVisveersspioenc.ifIiLeOdA, DVI=N
= 12V for
500 mA.
the
3.3V,
5V,
and
Adjustable
version,
VIN
=
25V
for
the
12V
version,
and
Symbol
Parameter
Conditions
LM2576-XX
LM2576HV-XX
Units
(Limits)
Typ Limit
(Note 2)
DEVICE PARAMETERS
Ib
Feedback Bias Current
VOUT = 5V (Adjustable Version Only)
fO Oscillator Frequency (Note 11)
50 100/500 nA
52 kHz
47/42
kHz
(Min)
58/63
kHz
(Max)
VSAT
Saturation Voltage
IOUT = 3A (Note 4)
1.4 V
1.8/2.0
V(Max)
DC Max Duty Cycle (ON)
(Note 5)
98 %
93 %(Min)
ICL Current Limit
(Notes 4, 11)
5.8 A
4.2/3.5
A(Min)
6.9/7.5
A(Max)
IL
Output Leakage Current
(Notes 6, 7): Output = 0V
2 mA(Max)
Output = −1V
7.5
mA
Output = −1V
30 mA(Max)
IQ Quiescent Current
(Note 6)
5 mA
10 mA(Max)
ISTBY
Standby Quiescent
Current
ON /OFF Pin = 5V (OFF)
50 µA
200 µA(Max)
θJA Thermal Resistance
θJA
θJC
θJA
T Package, Junction to Ambient (Note 8)
T Package, Junction to Ambient (Note 9)
T Package, Junction to Case
S Package, Junction to Ambient (Note 10)
65
45
2
50
˚C/W
5 www.national.com
5 Page 
LM2576 Series Buck Regulator Design Procedure (Continued)
INDUCTOR VALUE SELECTION GUIDES (For Continuous Mode Operation)
DS011476-9
FIGURE 3. LM2576(HV)-3.3
FIGURE 5. LM2576(HV)-12
DS011476-11
DS011476-10
FIGURE 4. LM2576(HV)-5.0
FIGURE 6. LM2576(HV)-15
DS011476-12
11 www.national.com
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet LB03.PDF ] | |
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