LM2611: EVM Instability

Ryan.Bishop

Part Number: LM2611

Hello,

We are experiencing instability with the LM2611 EVM.

Attached are some plots with notes about the setup and issue. We are suspecting the slope compensation values may be wrong for these operating conditions, or potentially Hopf bifurcation.

Can you verify this behavior? Can we share the actual slope compensation values used internally on the LM2611?

Thank you! Let me know if you have any questions,

over 6 years ago

0 Youhao Xi over 6 years ago

TI__Guru 68495 points

This can be a result of either gate jitters or subharmonics oscillation. Can you change the inductor to a higher inductance to see if the waveform becomes more stable?

This part is transferred to us and we need to search for the slope compensation info.

0 Nate Morrison70 over 6 years ago in reply to Youhao Xi

Prodigy 50 points

I will change the inductance and measure again.

I look forward to hearing about the slope compensation value.

0 Nate Morrison70 over 6 years ago in reply to Nate Morrison70

Prodigy 50 points

Here are the results at 47uH for the inductors. The downslope is now less than half. The jitter is now about half (50ns vs 100ns), but is still present.LM2611 Eval Board switching instability _2 w_47uH.pdf

Any update on the slope compensation value?

0 Youhao Xi over 6 years ago in reply to Nate Morrison70

TI__Guru 68495 points

We found the design database and after studied it. In referenced to the inductor current, there is ~300mA peak of slope compensation, which is 25% of the 1.2A current limit.

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LM2611: EVM Instability