LM2576HVS-ADJ National Semiconductor, LM2576HVS-ADJ Datasheet - Page 10

• Manufacturer Part Number: LM2576HVS-ADJ
• Description: Voltage Regulator IC
• Manufacturer: National Semiconductor

Specifications of LM2576HVS-ADJ

• Input Voltage: 60V
• No. Of Pins: 3
• Peak Reflow Compatible (260 C): No
• Termination Type: SMD
• Supply Voltage Max: 60V
• Leaded Process Compatible: No
• Package / Case: 3-TO-263
• Output Current Max: 3A
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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LM2576 Series Buck Regulator Design Procedure
Given:
V
(3.3V, 5V, 12V, or 15V)
V
I
1. Inductor Selection (L1)
A. Select the correct Inductor value selection guide from
Figures 3, 4, 5 or Figure 6 . (Output voltages of 3.3V, 5V,
12V or 15V respectively). For other output voltages, see
the design procedure for the adjustable version.
B. From the inductor value selection guide, identify the in-
ductance region intersected by V
and note the inductor code for that region.
C. Identify the inductor value from the inductor code, and
select an appropriate inductor from the table shown in
Figure 3 . Part numbers are listed for three inductor manu-
facturers. The inductor chosen must be rated for opera-
tion at the LM2576 switching frequency (52 kHz) and for a
current rating of 1.15 x I
formation, see the inductor section in the Application
Hints section of this data sheet.
2. Output Capacitor Selection (C
A. The value of the output capacitor together with the in-
ductor defines the dominate pole-pair of the switching
regulator loop. For stable operation and an acceptable
output ripple voltage, (approximately 1% of the output
voltage) a value between 100 µF and 470 µF is recom-
mended.
B. The capacitor’s voltage rating should be at least 1.5
times greater than the output voltage. For a 5V regulator,
a rating of at least 8V is appropriate, and a 10V or 15V
rating is recommended.
Higher voltage electrolytic capacitors generally have
lower ESR numbers, and for this reason it may be neces-
sary to select a capacitor rated for a higher voltage than
would normally be needed.
3. Catch Diode Selection (D1)
A.The catch-diode current rating must be at least 1.2
times greater than the maximum load current. Also, if the
power supply design must withstand a continuous output
short, the diode should have a current rating equal to the
maximum current limit of the LM2576. The most stressful
condition for this diode is an overload or shorted output
condition.
B. The reverse voltage rating of the diode should be at
least 1.25 times the maximum input voltage.
4. Input Capacitor (C
An aluminum or tantalum electrolytic bypass capacitor lo-
cated close to the regulator is needed for stable opera-
tion.
LOAD
OUT
IN
(Max) = Maximum Input Voltage
PROCEDURE (Fixed Output Voltage Versions)
(Max) = Maximum Load Current
= Regulated Output Voltage
IN
)
LOAD
. For additional inductor in-
IN
(Max) and I
OUT
)
LOAD
(Max),
10
Given:
V
V
I
1. Inductor Selection (L1)
A. Use the selection guide shown in Figure 4 .
B. From the selection guide, the inductance area inter-
sected by the 15V line and 3A line is L100.
C. Inductor value required is 100 µH. From the table in
Figure 3 . Choose AIE 415-0930, Pulse Engineering
PE92108, or Renco RL2444.
2. Output Capacitor Selection (C
A. C
lytic.
B.Capacitor voltage rating = 20V.
3. Catch Diode Selection (D1)
A.For this example, a 3A current rating is adequate.
B. Use a 20V 1N5823 or SR302 Schottky diode, or any of
the suggested fast-recovery diodes shown in Figure 8 .
4. Input Capacitor (C
A 100 µF, 25V aluminum electrolytic capacitor located
near the input and ground pins provides sufficient
bypassing.
LOAD
OUT
IN
(Max) = 15V
OUT
EXAMPLE (Fixed Output Voltage Versions)
(Max) = 3A
= 5V
= 680 µF to 2000 µF standard aluminum electro-
IN
)
OUT
)