LM5008AEVAL: Strange SW waveform

user4374604

Part Number: LM5008AEVAL

Just test the LM5008AEVM and find that the SW waveform is not so "standard" at the begining of HS MOS on phase. It will happen once the input voltage exceeds 50V. Why? SW waveform is attached.

Input: 80V. Output: 5V, 200mA

over 6 years ago

0 Katelyn Wiggenhorn over 6 years ago

TI__Genius 11040 points

Hello,

How are you measuring this waveform, meaning where is your test probe? Are you measuring with a 'tip and barrel' method?

www.eetimes.com/document.asp

Thank you,
Katelyn Wiggenhorn

0 user4374604 over 6 years ago in reply to Katelyn Wiggenhorn

Prodigy 20 points

Hi Katlyn,

Thank you for reply.

I just measure the SW test point on the EVM board. I think the method shold be correct.

0 Katelyn Wiggenhorn over 6 years ago in reply to user4374604

TI__Genius 11040 points

Hello,

Please use a tip and barrel method for sensing the switch node. This will reduce the loop area of the ground path. Please reference this post for an example of the tip and barrel method to accurately measure the switch node:

e2e.ti.com/.../2243.understanding-measuring-and-reducing-output-voltage-ripple

Thank you,
Katelyn

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LM5008AEVAL: Strange SW waveform