LM25139: LM25139RGTR

Koki Ida

Part Number: LM25139

I am using the LM25139RGTR in a 24 V-to-5 V buck converter design, but the circuit does not operate correctly. There is no switching voltage at the SW pin. However, if I reduce the capacitance of the electrolytic capacitor connected to the 5 V output, the converter starts operating normally. Could you explain why this occurs?

10 days ago

0 Oscar Ambriz 9 days ago

TI__Genius 15720 points

Hello Koki,

Could you please provide a schematic of the LM25139RGTR. Additionally are there any scope captures of the output voltage and switch node before and after the fix? Is there any other voltage source applied to the output prior to startup?

Looping in our device expert.

Regards,

Oscar Ambriz

0 Koki Ida 9 days ago in reply to Oscar Ambriz

Prodigy 10 points

0 Joshua Austria 7 days ago in reply to Koki Ida

TI__Mastermind 33680 points

Hi Koki,

What values did you use for your electrolytic capacitor, before and after the fix. Did you also try to re-mount the original electrolytic onto the board or try another same value unit? This will help to rule out an improper solder or defective cap unit.

Thank you,

Joshua Austria

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LM25139: LM25139RGTR