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LM5576 SW pin shorts with PGND

Other Parts Discussed in Thread: LM5576

Hi,


I am using LM5576 switching regulator in my design. Maximum input voltage in this design is 60V, output voltage is 13.6V, Load current is 300mA. While switching on the system, the regulator does not power up the system. This condition occurs randomly. input voltage drives from 12V, 42Ah Battery (4nos paralleled). After verified, it is found that the impedance at SW pin to PGND is 4.7ohms. The I removed the IC and measured the impedance on each pin with respect to GND and the results are below.

SW pin to GND - 21.7 ohms

PRE pin to GND - 388.5Kohms

IS pin to GND - 0.4ohms

VCC to AGND - 25.1ohms

Vin to AGND - open

I can not trouble shoot the root cause of the problem. Any one can help me to find out.