LM25149-Q1: comparison between LM25149-Q1 and LM25141-Q1

wang nick

Part Number: LM25149-Q1
Other Parts Discussed in Thread: LM25141-Q1, , LM25148-Q1

Tool/software:

Hi there!

We have an EMI issue caused by LM25141-Q1, so we are evaluating the feasibility of replacing the LM25141-Q1 with the LM25149-Q1. Due to time constraints, I’d like to confirm if the key differences between these two power controllers are primarily the Active EMI Filter and Dual Random Spread Spectrum (DRSS).

Additionally, I noticed in the datasheet that "DRSS is disabled when an external clock is applied to the PFM/SYNC pin." So this means that if we use an independent external clock (via PFM/SYNC pin) to operate in PFM mode, DRSS will be disabled, my question is: "Is PFM mode beneficial for improving EMC performance?"

thanks a lot.

4 months ago

+1 Timothy Hegarty 4 months ago

TI__Guru 73402 points

Hello,

The LM25148-Q1 (no AEF) and LM25149-Q1 (with AEF) both provide DRSS, which is an enhanced spread spectrum technique relative to the triangular spread spectrum used in the LM25141-Q1. Depending on the frequency of the EMI issue, this may provide an improvement. In particular, DRSS should be better for 30+MHz noise.

DRSS is disabled with an external clock, as the frequency is fixed. The operation will be FPWM, not PFM. PFM is only to improve light-load efficiency.

Regards,

Tim

+1 wang nick 4 months ago in reply to Timothy Hegarty

Prodigy 80 points

I got it, thank you so much, Timothy.

0 Timothy Hegarty 4 months ago in reply to wang nick

TI__Guru 73402 points

Thanks for the question.

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LM25149-Q1: comparison between LM25149-Q1 and LM25141-Q1