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LM339: LM339 noise at the reference pin

Part Number: LM339

Hi Team,

My customer has a cooker working normally for 5 years. Now they changed the manufacturing factory, problem occurred.

there has a noise at the ref pin of LM339, resulting in fause trigger of the IGBT when turning up the input power of the cooker. 

Green is the waveform at the ref pin, yellow is the IGBT drive signal.

So, do you have some ideas about this issue? (Note that this issue occurred after changing the manufacturing factory, it worked well before this)

Thanks a lot,

Yang