LM2576-XX
LM2576 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-
ableinfixedoutputvoltagesof3.3V,5V,12V,andan
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,andadjustableoutputversions
n
Adjustable version output voltage range,
1.23Vto37V
±
4% max over
line and load conditions
n
Guaranteed 3A output current
n
Wideinputvoltagerange,40V
n
n
n
n
n
n
n
Requires only 4 external components
52 kHz fixed frequency internal oscillator
TTL shutdown capability, low power standby mode
High efficiency
Uses readily available standard inductors
Thermal shutdown and current limit protection
P+ Product Enhancement tested
Applications
n
n
n
n
Simple high-efficiency step-down (buck) regulator
Efficient pre-regulator for linear regulators
On-card switching regulators
Positive to negative converter (Buck-Boost)
Typical Application
(Fixed Output Voltage Versions)
FIGURE 1.
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1
2018 AUG
LM2576-XX
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over full Operating Temperature
Range.
Symbol
Parameter
Conditions
Typ
SYSTEM PARAMETERS
(Note 3)
Test Circuit
Figure 2
V
OUT
Feedback Voltage
V
IN
= 12V, I
LOAD
= 0.5A
V
OUT
= 5V,
Circuit of
Figure 2
V
OUT
Feedback Voltage
LM2576
0.5A
≤
I
LOAD
≤
3A,
8V
≤
V
IN
≤
40V
V
OUT
= 5V, Circuit of
Figure 2
1.230
1.193/1.180
1.267/1.280
1.230
1.217
1.243
V
V(Min)
V(Max)
V
V(Min)
V(Max)
LM2576-ADJ
Limit
(Note 2)
Units
(Limits)
η
Efficiency
V
IN
= 12V, I
LOAD
= 3A, V
OUT
= 5V
77
%
All Output Voltage Versions Electrical Characteristics
Specifications with standard type face are for T
J
= 25˚C, and those with
boldface type
apply over full Operating Temperature
Range. Unless otherwise specified, V
IN
= 12V for the 3.3V, 5V, and Adjustable version, V
IN
= 25V for the 12V version, and V
IN
= 30V for the 15V version. I
LOAD
= 500 mA.
Symbol
Parameter
Conditions
LM2576-XX
Typ
DEVICE PARAMETERS
I
b
f
O
Feedback Bias Current
Oscillator Frequency
V
OUT
= 5V (Adjustable Version Only)
(Note 11)
50
52
47/42
58/63
V
SAT
DC
I
CL
Saturation Voltage
Max Duty Cycle (ON)
Current Limit
I
OUT
= 3A (Note 4)
(Note 5)
(Notes 4, 11)
1.4
1.8/2.0
98
93
5.8
4.2/3.5
6.9/7.5
I
L
Output Leakage Current
(Notes 6, 7): Output = 0V
Output = −1V
Output = −1V
I
Q
I
STBY
Quiescent Current
Standby Quiescent
Current
(Note 6)
ON /OFF Pin = 5V (OFF)
5
10
50
200
7.5
30
2
100/500
nA
kHz
kHz
(Min)
kHz
(Max)
V
V(Max)
%
%(Min)
A
A(Min)
A(Max)
mA(Max)
mA
mA(Max)
mA
mA(Max)
µA
µA(Max)
Limit
(Note 2)
Units
(Limits)
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5
2018 AUG
嵌入式系统
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