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LM5140-Q1: Switch node jitter

Thomas Sagcob
Prodigy 75 points
Part Number: LM5140-Q1
Other Parts Discussed in Thread: LM25119

Hi,

I've designed a 5V/13A power supply with LM5140-Q1using interleaved mode (2*6,5A) @ 440kHz. The circuit is working so far.

Problem: at 12V input the average duty cycle is ~ 40%, but with a jitter of +/- 15%!

So duty cycle varies in a range from 25% to 55%; at light load as well as heavy load.

In a similar circuit (0V85/2*13A) out of 5V with LM25119 in interleaved mode, the duty cyle is 17% with only +/- 0,2% switching jitter.

The layout is (IMO) well designed, the compensation is TI-FAE optimized.

Any idea, how to reduce this jitter?

Thanks in advance

Thomas

  • 0
    TI__Expert 3545 points

    Thomas,

    I've designed the LM5140 in an interleaved mode, but I've never seen the jitter as high as you’re seeing it.  Normally +/- 5% is what I have seen.  At light load are you seeing the LM5140 in a pulse skipping mode which is normal?  Can you send me your schematics and the switch node waveforms under the two operating modes, light load and heavy load?

    Terry