LM2576, LM2576HV

SNVS107C – JUNE 1999 – REVISED APRIL 2013

www.ti.com

LM2576 Series Buck Regulator Design Procedure

PROCEDURE (Fixed Output Voltage Versions)

EXAMPLE (Fixed Output Voltage Versions)

Given:

Given:

(3.3V, 5V, 12V, or 15V)

1. Inductor Selection (L1)

1. Inductor Selection (L1)

A. Select the correct Inductor value selection guide from Figure 23, A. Use the selection guide shown in Figure 24.

Figure 24, Figure 25, or Figure 26. (Output voltages of 3.3V, 5V, 12V B. From the selection guide, the inductance area intersected by the

or 15V respectively). For other output voltages, see the design 15V line and 3A line is L100.

procedure for the adjustable version.

C. Inductor value required is 100

μH. From the table in Figure 23.

B. From the inductor value selection guide, identify the inductance Choose AIE 415-0930, Pulse Engineering PE92108, or Renco

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 23. Part

numbers are listed for three inductor manufacturers. The inductor

chosen must be rated for operation at the LM2576 switching

additional inductor information, see INDUCTOR SELECTION.

defines the dominate pole-pair of the switching regulator loop. For B.Capacitor voltage rating = 20V.

stable

operation

and

an

acceptable

output

ripple

voltage,

(approximately 1% of the output voltage) a value between 100

μF

and 470

μF is recommended.

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 necessary to select a

capacitor rated for a higher voltage than would normally be needed.

3. Catch Diode Selection (D1)

3. Catch Diode Selection (D1)

A.The catch-diode current rating must be at least 1.2 times greater A.For this example, a 3A current rating is adequate.

than the maximum load current. Also, if the power supply design B. Use a 20V 1N5823 or SR302 Schottky diode, or any of the

must withstand a continuous output short, the diode should have a suggested fast-recovery diodes shown in Table 1.

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.

An aluminum or tantalum electrolytic bypass capacitor located close A 100

μF, 25V aluminum electrolytic capacitor located near the input

to the regulator is needed for stable operation.

and ground pins provides sufficient bypassing.

12

Submit Documentation Feedback

Copyright © 1999–2013, Texas Instruments Incorporated

Product Folder Links: LM2576 LM2576HV