TPS543C20: TPS543C20RVFT : High input ripple issue

jitheesh pathayapurakkal

Part Number: TPS543C20

We using stackable TPS543C20RVFT regulator in our project for providing 0.85 V for Zynq Ultrascale+ SoC (19EG). Input 5 V for both master & slave is provided through ferrite bead (Pi Filter). In 5V input we getting around 28.8mV ripple whereas After the Master input ferrite bead 57.6mV and after slave input ferrite bead 86.4mV (Please check the waveforms)

Can i please know why there is increase in amplitude of the ripple after the ferrite beads?

Circuit Diagram also given below

over 5 years ago

0 Yuchang Zhang over 5 years ago

TI__Mastermind 18510 points

The “after bead” should be the PVIN of Buck converter, right? As we know, when buck works, high-side mosfet will turn on and turn off under switching Frequency, this will cause the input current discontinuous, which willl cause high frequency noise at input line as well, The bead is helpful to filter the high frequency noise to the Vcc-5V bus, so you can see the ripple is smaller before the bead.

Yuchang

0 jitheesh pathayapurakkal over 5 years ago in reply to Yuchang Zhang

Prodigy 50 points

Thanks for your reply. If that is the case how we can reduce the ripple in PVIN side of the regulator?

0 Yuchang Zhang over 5 years ago in reply to jitheesh pathayapurakkal

TI__Mastermind 18510 points

More input filter,more better, such as more input caps

And for layout, suggest you can add one 0.1uf closest to PVIN pin, and Two stage of input LC filters will be much better

Yuchang

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TPS543C20: TPS543C20RVFT : High input ripple issue