Application Information (Continued)

INVERTING REGULATOR SHUTDOWN METHODS

To use the ON /OFF pin in a standard buck configuration is

simple, pull it below 1.3V (@25˚C, referenced to ground) to

turn regulator ON, pull it above 1.3V to shut the regulator

OFF. With the inverting configuration, some level shifting is

required, because the ground pin of the regulator is no

longer at ground, but is now setting at the negative output

voltage level. Two different shutdown methods for inverting

regulators are shown in

Figure 27 and 28.

01258342

FIGURE 27. Inverting Regulator Ground Referenced Shutdown

01258343

FIGURE 28. Inverting Regulator Ground Referenced Shutdown using Opto Device

14

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LM2575

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LM2575

/LM2575HV

5.0

2A Step-Down Voltage Regulator

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UMW LM2575/LM2575HV

UMW LM2575/LM2575HV