LM2575T-12 National Semiconductor, LM2575T-12 Datasheet - Page 14

• Manufacturer Part Number: LM2575T-12
• Description: Voltage Regulator IC
• Manufacturer: National Semiconductor

Specifications of LM2575T-12

• No. Of Pins: 5
• Output Current: 1A
• Peak Reflow Compatible (260 C): No
• Output Voltage: 12V
• Termination Type: Through Hole
• Supply Voltage Max: 40V
• Leaded Process Compatible: No
• Mounting Type: Through Hole
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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INDUCTOR VALUE SELECTION GUIDES
3. Output Capacitor Selection (C
A. The value of the output capacitor together with the inductor
defines the dominate pole-pair of the switching regulator loop.
For stable operation, the capacitor must satisfy the following
requirement:
The above formula yields capacitor values between 10 µF and
2000 µF that will satisfy the loop requirements for stable
operation. But to achieve an acceptable output ripple voltage,
(approximately 1% of the output voltage) and transient re-
sponse, the output capacitor may need to be several times
larger than the above formula yields.
B. The capacitor’s voltage rating should be at last 1.5 times
greater than the output voltage. For a 10V regulator, a rating
of at least 15V or more is recommended.
Higher voltage electrolytic capacitors generally have lower
ESR numbers, and for this reasion it may be necessary to
select a capacitor rate for a higher voltage than would nor-
mally be needed.
4. 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 LM2575. The most stressful condition for
this diode is an overload or shorted output. See diode selec-
tion guide in Figure 8 .
B. The reverse voltage rating of the diode should be at least
1.25 times the maximum input voltage.
5. Input Capacitor (C
An aluminum or tantalum electrolytic bypass capacitor located
close to the regulator is needed for stable operation.
To further simplify the buck regulator design procedure, National Semiconductor is making available computer design software to
be used with the Simple Switcher line of switching regulators. Switchers Made Simple (version 3.3) is available on a (3
diskette for IBM compatible computers from a National Semiconductor sales office in your area.
PROCEDURE (Adjustable Output Voltage Versions)
IN
)
OUT
)
14
3. Output Capacitor Selection (C
A.
However, for acceptable output ripple voltage select
C
C
4. Catch Diode Selection (D1)
A. For this example, a 3A current rating is adequate.
B. Use a 40V MBR340 or 31DQ04 Schottky diode, or any of
the suggested fast-recovery diodes in Figure 8 .
5. Input Capacitor (C
A 100 µF aluminum electrolytic capacitor located near the
input and ground pins provides sufficient bypassing.
OUT
OUT
(For Continuous Mode Operation) (Continued)
EXAMPLE (Adjustable Output Voltage Versions)
= 220 µF electrolytic capacitor
220 µF
IN
)
OUT
)
1
⁄
2
")