LM2576 datasheet(20/46 Pages) TI

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2. From the inductor value selection guide, identify the inductance region intersected by VIN(Max) and

ILOAD(Max), and note the inductor code for that region. From the selection guide, the inductance area

intersected by the 15-V line and 3-A line is L100.

3. Identify the inductor value from the inductor code, and select an appropriate inductor from the table shown

in Figure 8-4. Part numbers are listed for three inductor manufacturers. The inductor chosen must be rated

for operation at the LM2576 switching frequency (52 kHz) and for a current rating of 1.15 × ILOAD. For

additional inductor information, see Section 8.1.2. Inductor value required is 100 μH from the table in Figure

8-4. Choose AIE 415-0930, Pulse Engineering PE92108, or Renco RL2444.

8.2.1.2.3 Output Capacitor Selection (COUT)

1. The value of the output capacitor together with the inductor 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) TI recommends a value between 100 μF and 470 μF. We choose COUT = 680-μF to 2000-μF

standard aluminum electrolytic.

2. The voltage rating of the capacitor must be at least 1.5 times greater than the output voltage. For a 5-V

regulator, a rating of at least 8 V is appropriate, and TI recommends a 10-V or 15-V rating. Capacitor voltage

rating = 20 V. Higher voltage electrolytic capacitors generally have lower ESR numbers, and for this reason it

can be necessary to select a capacitor rated for a higher voltage than can normally be needed.

8.2.1.2.4 Catch Diode Selection (D1)

1. 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 must 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. For this example, a 3-A current rating is adequate.

2. The reverse voltage rating of the diode must be at least 1.25 times the maximum input voltage. Use a 20-V

1N5823 or SR302 Schottky diode, or any of the suggested fast-recovery diodes shown in Table 8-3.

8.2.1.2.5 Input Capacitor (CIN)

An aluminum or tantalum electrolytic bypass capacitor located close to the regulator is needed for stable

operation. A 100-μF, 25-V aluminum electrolytic capacitor located near the input and ground pins provides

sufficient bypassing.

LM2576, LM2576HV

SNVS107G – JUNE 1999 – REVISED MARCH 2023

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LM2576 Datasheet(PDF) 20 Page - Texas Instruments