TPS53355: I see large switching spike from our setup using model specs

Harjot Singh

Part Number: TPS53355

Hi,

We have a setup using the model in WEBENCH. The setup we have is 1.9V input to Vin and we are outputting 1.35V. Current max is 20A. For the inductor we are using 120nH (VSLC7649S-121KLB)

and 6 100uF ceramic caps (LMK325BJ107MM-T)

We see the large spikes from the scope when measuring near the Vout with very short gnd. The spikes we see are reaching about 500 to 600mV.

Wondering if this normal to see with this setup and if any improvement can be made?

Thanks Jot

over 6 years ago

0 JohnTucker over 6 years ago

TI__Guru**** 191445 points

Harjot,

Can we see your schematic, PCB layout and waveform?

0 Harjot Singh over 6 years ago in reply to JohnTucker

Prodigy 30 points

Hi Yes,

Here is the layout. I have a feeling the GNDs may have some effect. Also posted a scopeshot.

0 JohnTucker over 6 years ago in reply to Harjot Singh

TI__Guru**** 191445 points

Harjot,

I see you already have a snubber and a BOOT resistor. You can attempt to optimize the values to decrease the switching noise. Your other option is to add some HF bypass capacitors at the output. 0.1 uF, 0.01 uF and 0.001 uF. If that does not work you can try a secondary LC filter. Very likely the second L can be a ferrite bead.

0 Harjot Singh over 6 years ago in reply to JohnTucker

Prodigy 30 points

Hi John,

Thanks for the reply. I had one last question. Can noise coming into the VDD cause issues to the Vout? The Vin is nice and clean but i do have noise being transmitted into VDD from a 12.5V

Thanks

Jot

0 JohnTucker over 5 years ago in reply to Harjot Singh

TI__Guru**** 191445 points

Jot,

Vdd is very much noise sensitive. I doubt that it is the cause of your switching noise though.

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TPS53355: I see large switching spike from our setup using model specs