3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 1 - HTC
FEATURES
” 3.3V, 5.0V, 12V and Adjustable Output Versions
” Adjustable Version Output Voltage Range, 1.23 to 37V
+/- 4% AG10Maximum Over Line and Load Conditions
” Guaranteed 3.0A Output Current
” Wide Input Voltage Range
” Requires Only 4 External Components
” 52kHz Fixed Frequency Internal Oscillator
” TTL Shutdown Capability, Low Power Standby Mode
” High Efficiency
” Uses Readily Available Standard Inductors
” Thermal Shutdown and Current Limit Protection
” Moisture Sensitivity Level 3 for SMD packages
APPLICATION
” Simple High-Efficiency Step-Down(Buck) Regulator
” Efficient Pre-Regulator for Linear Regulators
” On-Card Switching Regulators
” Positive to Negative Converter(Buck-Boost)
” Negative Step-Up Converters
” Power Supply for Battery Chargers
SOP8-PP PKG
TO-220 PKG
TO-263 PKG
ORDERING INFORMATION
Device Marking Package
LM2576DP-X.X LM2576-X.X SOP8-PP
LM2576T-X.X LM2576-X.X TO-220
LM2576R-X.X LM2576-X.X TO-263
DESCRIPTION
The LM2576 series of regulators are monolithic integrated circuits ideally suited for easy and convenient
design of a step-down switching regulator (buck converter).
All circuits of this series are capable of driving a 3.0A load with excellent line and load regulation. These
devices are available in fixed output voltages of 3.3V, 5.0V, 12V and an adjustable output version.
These regulators were designed to minimize the number of external components to simplify the power supply
design. Standard series of inductors optimized for use with the LM2576 are offered by several different inductor
manufacturers.
Since the LM2576 converter is a switch-mode power supply, its efficiency is significantly higher in comparison
with popular three-terminal linear regulators, especially with higher input voltages.
In many cases, the power dissipated is so low that no heatsink is required or its size could be reduced
dramatically. 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. The LM2576
features include a guaranteed +/- 4% tolerance on output voltage within specified input voltages and output
load conditions, and +/-10% on the oscillator frequency (+/- 2% over 0C to 125C).
External shutdown is included, featuring 80(typical) standby current. The output switch includes cycle-
bycycle current limiting, as well as thermal shutdown for full protection under fault conditions.
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 2 - HTC
Ordering Information
VOUT Package Order No. Description Package Marking Status
ADJ
SOP8-PP LM2576DP-ADJ 3A, Adjustable, 52kHz, On/off LM2576-ADJ Contact Us
TO220-5L LM2576T-ADJ 3A, Adjustable, 52kHz, On/off LM2576-ADJ Active
TO263-5L LM2576R-ADJ 3A, Adjustable, 52kHz, On/off LM2576-ADJ Active
3.3V
SOP8-PP LM2576DP-3.3 3A, Fixed, 52kHz, On/off LM2576-3.3 Contact Us
TO220-5L LM2576T-3.3 3A, Fixed, 52kHz, On/off LM2576-3.3 Active
TO263-5L LM2576R-3.3 3A, Fixed, 52kHz, On/off LM2576-3.3 Active
5.0V
SOP8-PP LM2576DP-5.0 3A, Fixed, 52kHz, On/off LM2576-5.0 Contact Us
TO220-5L LM2576T-5.0 3A, Fixed, 52kHz, On/off LM2576-5.0 Active
TO263-5L LM2576R-5.0 3A, Fixed, 52kHz, On/off LM2576-5.0 Active
12V
SOP8-PP LM2576DP-12 3A, Fixed, 52kHz, On/off LM2576-12 Contact Us
TO220-5L LM2576T-12 3A, Fixed, 52kHz, On/off LM2576-12 Active
TO263-5L LM2576R-12 3A, Fixed, 52kHz, On/off LM2576-12 Active
Root Name
Product Code
LM 2576
Package Type DP : SOP8-PP
T : TO220-5L
R : TO263-5L
Output Voltage : ADJ / 3.3V / 5.0V /12V
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 3 - HTC
PIN CONFIGURATION
SOP8-PP TO220-5L TO263-5L
PIN DESCRIPTION
Package
Symbol Description
TO-220 5L
TO-263 5L
SOP8-PP
1 1 VIN
This pin is the positive input supply for the LM2576 step–down
switching regulator.
In order to minimize voltage transients and to supply the switching
currents needed by the regulator, a suitable input bypass capacitor
must be present. (Cin in Figure 1).
2 2 VOUT
This is the emitter of the internal switch. The saturation voltage
VSAT of this output switch is typically 1.5V. It should be kept in mind
that the PCB area connected to this pin should be kept to a
minimum in order to minimize coupling to sensitive circuitry.
3 6 GND
Circuit ground pin. See the information about the printed circuit
board layout.
4 3 FEEDBACK
This pin senses regulated output voltage to complete the feedback
loop.
The signal is divided by the internal resistor divider network R2, R1
and applied to the non–inverting input of the internal error amplifier.
In the adjustable version of the LM2576 switching regulator this pin
is the direct input of the error amplifier and the resistor network R2,
R1 is connected externally to allow programming of the output
voltage.
5 4 ON/OFF
It allows the switching regulator circuit to be shutdown using logic
level signals, thus dropping the total input supply current to
approximately 80uA.
The threshold voltage is typically 1.4V. Applying a voltage above
this value (up to +Vin) shuts the regulator off. If the voltage applied
to this pin is lower than 1.4V or if this pin is left open, the regulator
will be in the "on" condition
- 5, 7, 8 N.C. No Connect.
* Exposed Pad of SOP8-PP package should be externally connected to GND.
Exposed
PAD
VIN 1
VOUT 2
FEEDBACK 3
ON/OFF 4
8 N.C
7 N.C
6 GND
5 N.C.
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 4 - HTC
Typical Application (Fixed Output Voltage Versions)
Figure 1. Block Diagram and Typical Application
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 5 - HTC
ABSOLUTE MAXIMUM RATINGS
(Absolute Maximum Ratings indicate limits beyond which damage to the device may occur)
Rating Symbol Value UNIT
Maximum Supply Voltage Vin 45 V
On/Off Pin Input Voltage - -0.3V V +Vin V
Output Voltage to Ground (Steady-State) - -1.0 V
Power Dissipation
SOP8-PP 8Lead
Thermal Resistance, Junction to Ambient
Thermal Resistance, Junction to Case
PD
JA
JC
Internally Limited
Contact us
Contact us
W
/W
/W
TO-220 5Lead PD Internally Limited W
Thermal Resistance, Junction to Ambient J
A
65 /W
Thermal Resistance, Junction to Case JC 5 /W
TO-263 5Lead PD Internally Limited W
Thermal Resistance, Junction to Ambient J
A
70 /W
Thermal Resistance, Junction to Case JC 5 /W
Storage Temperature Range TSTG -60 to +150
Minimum ESD Rating(Human Body Model: - 2.0 kV
C=100 pF, R=1.5k
Lead Temperature (Soldering, 10seconds) - 260
Maximum Junction Temperature TJ 150
OPERATING RATINGS (Operating Ratings indicate conditions for which the device is intended to be
functional, but do not guarantee specific performance limits. For guaranteed specifications, see the
Electrical Characteristics.)
Rating Symbol Value. Unit
Operating Junction Temperature Range TJ -40 to +125
Supply Voltage Vin 40 V
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 6 - HTC
ELECTRICAL CHARACTERISTICS / SYSTEM PARAMETERS ([Note 1] Test Circuit Figure 15)
(Unless otherwise specified, Vin = 12V for the 3.3V, 5.0V, and Adjustable version, Vin = 25V for the 12V version.
ILoad = 500 mA. For typical values TJ = 25°C, for min/max values TJ is the operating junction temperature range
that applies [Note 2], unless otherwise noted.)
Characteristics Symbol Min TYP Max Unit
LM2576-3.3V ([Note 1] Test Circuit Figure 2)
Output Voltage (Vin = 12V, ILOAD=0.5A, TJ=25) Vout 3.234 3.3 3.366 V
Output Voltage (6.0V≤Vin≤40V, 0.5A≤ILOAD≤3.0A
Vout
V
TJ=25 3.168 3.3 3.432
TJ= -40 ~ +125 3.135 - 3.465
Efficiency (Vin=12V, ILOAD=3.0A) - 75 - %
LM2576-5.0V ([Note 1] Test Circuit Figure 2)
Output Voltage (Vin = 12V, ILOAD=0.5A, TJ=25) Vout 4.9 5.0 5.1 V
Output Voltage (8.0V≤Vin≤40V, 0.5A≤ILOAD≤3.0A
Vout
V
TJ=25 4.8 5.0 5.2
TJ= -40 ~ +125 4.75 - 5.25
Efficiency (Vin=12V, ILOAD=3.0A) - 77 - %
LM2576-12V ([Note 1] Test Circuit Figure 2)
Output Voltage (Vin = 25V, ILOAD=0.5A, TJ=25) Vout 11.76 12 12.24 V
Output Voltage (15V≤Vin≤40V, 0.5A≤ILOAD≤3.0A
Vout
V
TJ=25 11.52 12 12.48
TJ= -40 ~ +125 11.4 - 12.6
Efficiency (Vin=25V, ILOAD=3.0A) - 88 - %
LM2576-ADJ ([Note 1] Test Circuit Figure 2)
Feedback Voltage (Vin=12V, ILOAD=0.5A, TJ=25) Vout 1.217 1.23 1.243 V
Feedback Voltage (8.0V≤Vin≤40V, 0.5A≤ILOAD≤3.0A, Vout=5.0V)
Vout
V
TJ=25 1.193 1.23 1.267
TJ= -40 ~ +125 1.18 - 1.28
Efficiency (Vin=12V, ILOAD=3.0A, Vout=5.0V) - 77 - %
1. External components such as the catch diode, inductor, input and output capacitors can affect switching
regulator system performance.
When the LM2576 is used as shown in the Figure 15 test circuit, system performance will be as shown in
system parameters section.
2. Tested junction temperature range for the LM2576: Tlow = –40°C Thigh = +125°C
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 7 - HTC
ELECTRICAL CHARACTERISTICS / Device Parameters
(Unless otherwise specified, Vin = 12V for the 3.3V, 5.0V, and Adjustable version, Vin = 25V for the 12V version.
ILoad = 500 mA. For typical values TJ = 25°C, for min/max values TJ is the operating junction temperature range
that applies [Note 2], unless otherwise noted.)
Characteristics Symbol MIN. TYP. MAX. Unit
All Output Voltage Versions
Feedback Bias Current (Vout=5.0V [Adjustable Version Only])
TJ=25
TJ= -40 to +125
Ib
-
-
25
-
100
200 nA
Oscillator Frequency [Note 3]
TJ=25
TJ= 0 to +125
TJ= -40 to +125
FOSC
-
47
42
52
-
-
-
58
63
kHz
Saturation Voltage (Iout=3.0A [note 4])
TJ= 25
TJ= -40 to +125
VSAT
-
-
1.5
-
1.8
2
V
Max Duty Cycle (“0”) [Note 5] DC 94 98 - %
Current Limit (Peak Current [Note 3 and 4])
TJ= 25
TJ= -40 to +125
ICL
4.2
3.5
5.8
-
6.9
7.5
A
Output Leakage Current [Note 6 and 7], TJ=25
Output = 0V
Output = -1.0V
IL
-
-
0.8
6
50
30 mA
Quiescent Current [Note 6]
TJ= 25
TJ= -40 to +125
IQ
-
-
5
-
9
11 mA
Standby Quiescent Current (ON/OFF Pin = 5.0V ("off"))
TJ=25
TJ= -40 to +125
ISTBY
-
-
80
-
200
400 µA
ON/OFF Pin Logic Input Level (Test circuit Figure 15)
Vout=0V
TJ=25
TJ= -40 to +125
VIH
2.2
2.4
1.4
-
-
-
V
Vout=Nominal Output Voltage
TJ=25
TJ= -40 to +125
VIL
-
-
1.2
-
1
0.8
V
ON/OFF Pin Input Current (Test Circuit Figure 15)
ON/OFF Pin = 5.0V (Regulator OFF), TJ=25
ON/OFF Pin = 0V (Regulator ON), TJ=25
IIH
IIL
-
-
15
0
30
0.5
µA
3. The oscillator frequency reduces to approximately 18 kHz in the event of an output short or an overload which causes the
regulated output voltage to drop approximately 40% from the nominal voltage. This self protection feature lowers the
average dissipation of the IC by lowering the minimum duty cycle from 5% down to approximately 2%
4. Output sourcing current. No diode, inductor or capacitor connected to output pin.
5. Feedback removed from output and connected to 0V.
6. Feedback removed from output and connected to +12V for the Adjustable, 3.3V, and 5.0V versions, and +25V for the 12V
version, to force the output transistor “off”.
7. Vin = 40V.
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 8 - HTC
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)
Figure 2. Normalized Output Voltage Figure 3. Line Regulation
Figure 4. Dropout Voltag e Figure 5. Current Limit
Figure 6. Quiescent Current Figure 7. Standby Quiescent Current
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 9 - HTC
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)
Figure 8. Standby Quiescent Current Figure 9. Switch Saturation Voltage
Figure 10. Oscillator Frequency Figure 11. Minimum Operating Voltage
Figure 12. Feedback Pin Current
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 10 - HTC
TYPICAL PERFORMANCE CHARACTERISTICS
Vout = 15V
A : Output Pin Voltage, 10V/DIV
B: Inductor Current, 2.0A/DIV
C: Inductor Current, 2.0A/DIV
D: Output Ripple Voltage, 50mV/dDIV, AC-Coupled
Horizontal Time Base : 5.0 µs/DIV
Figure 13. Switching Waveforms Figure 14. Load Transient Response
3A, 52kHz, Step-Down Switching Regulator LM2576
Dec 2011 – Rev. 1.3 - 11 - HTC
Cin - 100µF, 75V, Aluminium Electrolytic
Cout - 1000µF, 25V, Aluminium Electrolytic
D1 - Schottky, MBR360
L1 -100 µH, Pulse Eng. PE-92108
R1 - 2.0 k, 0.1%
R2 - 6.12 k, 0.1%
)0.1
V
V
(1R=2R
ref
out -
Where Vref = 1.23V, R1 between 1.0k and 5.0k
)
1R
2R
+0.1(V=V refout
Figure 15. Typical Test Circuit
