about the output wave of TPS53513

when i disconnect the load, the ripple become the sine wave(100mv Vpp) and the frequency is about 200KHz，

Can I see the SW node as well?

Hi,

Thanks for your relay.

when i connect another  10uf cap at the output, the ripple chang from the sine to the wave show in the picture following when disconnect load.

(the dcdc freqency is 400kHz)

SW note wave. DC couple . disconnect load.(now i change the dcdc frequency from 400kHz to 750KHz)

 

Thank you very much.

Hi,John

Because I have not ever saw so serious periodic square overshoot in the ripple, i think there may some errors in the design.

Now,i chang the L from 1.5uH to 3.3uH and the square disapper and the ripple down to 25mv Vpp.

Thank you very much.

The square portion on you last Vout waveform is due to ESL or other stray inductance. It is normal in my opinion. I would have to see the SW node waveform from your first waveforms to make any opinion.