LM2576 datasheet(13/46 Pages) TI

13 / 46 page

20 k

10 k

CIN

+VIN

LM2576-XX

GND

+VIN

ON/OFF

Complete circuit not shown.

Figure 7-1. Undervoltage Lockout for Buck Circuit

20 k

10 k

CIN

+VIN

LM2576-XX

+VIN

ON/OFF

-VOUT

GND

Complete circuit not shown (see Figure 8-1).

Figure 7-2. Undervoltage Lockout for Buck-Boost Circuit

7.3.2 Delayed Start-Up

The ON /OFF pin can be used to provide a delayed start-up feature as shown in Figure 7-3. With an input

voltage of 20 V and for the part values shown, the circuit provides approximately 10 ms of delay time before the

circuit begins switching. Increasing the RC time constant can provide longer delay times. But excessively large

RC time constants can cause problems with input voltages that are high in 60-Hz or 120-Hz ripple, by coupling

the ripple into the ON /OFF pin.

7.3.3 Adjustable Output, Low-Ripple Power Supply

Figure 7-4 shows a 3-A power supply that features an adjustable output voltage. An additional LC filter that

reduces the output ripple by a factor of 10 or more is included in this circuit.

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LM2576, LM2576HV

SNVS107G – JUNE 1999 – REVISED MARCH 2023

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LM2576 Datasheet(PDF) 13 Page - Texas Instruments