LM5141: SW RING

cassius Dai

Part Number: LM5141

I increased the HS shut down resistor, why can I also reduce SW ringing.IS SW ring be related to the High side Mosfet shutdown speed?

over 1 year ago

0 Daniel Louis over 1 year ago

TI__Intellectual 2160 points

Hi Cassius,

Please post a picture of your schematic, I/O values, load, and any relevant waveforms.

Thanks

0 Timothy Hegarty over 1 year ago in reply to Daniel Louis

TI__Guru 64297 points

Hi Cassius,

Take a look at these app notes for more detail on switch-node ringing:

www.ti.com/lit/snva803

www.ti.com/lit/slyt682

What's critical is the input cap placement (relative to the FETs) to minimize the power-loop parasitic inductance.

Regards,

Tim

0 cassius Dai over 1 year ago in reply to Daniel Louis

TI__Prodigy 40 points

I changed Rhoff from 10Ω to 0Ω,SW voltage has changed from 19V to 17.8V

0 Timothy Hegarty over 1 year ago in reply to cassius Dai

TI__Guru 64297 points

Hi Cassius,

If you're talking about leading edge ringing (on the rising edge of the SW voltage), then it should relate to the HO turn-on resistor. The HO off resistor sets the turn-off rate.

Note you can set the low-side gate resistors to 0Ω (especially the LO turn on resistor). What FETs are you using here?

FYI, I attached a high-density 2.1MHz design here with particularly low switch ringing. Note the capacitor placement on slide 7 (both 1210 and 0402) and layer stackup shown in slide 21.

Regards,

Tim

LM25141-Q1 15A, 2.1MHz high-density design.pdf

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LM5141: SW RING