TPS562200: Feed Forward Capacitor

Tateo,

I will check it for you.  As you know,  China team is in National Holiday,  so will give you feedback on 10/8 .

Hi,

Thank you for your reply. We look forward to your feedback. Thank you for your cooperation.

Best Regards,

tateo

Hi, Are there any update on that?

And we got additional question.

Now the big output voltage ripple is occurred at the light load on their own board. Their layout is similar to below layout which from SLVA922. As the APP note mentioned, in order to SW is close to FB, the SW noise badly affect to FB. Therefore we assume the layout causes the big output voltage ripple. But they'd rather not change the layout due to design schedule. So they tried to add 100pF Cff and the ripple is improved.

- According to the user's guide of EVM, the recommended maximum Cff is 10pF. Why is Cff limited to 10pF?

- If they use 100pF Cff, are there any concerns on this usage?

- Are there the waveform of the output voltage ripple at the light load by the layout version 2 from SLVA922?

- Customer condition -
Vin=12V
Vout=3.3V
Iout=1mA to 1A
L=4.7uH
Cout=22uF(16V)*2pcs

Best Regards,
tateo

Hi,

The forward capacitor is useful for the loop, I am asking the writer why it was deleted, will give you the answer later.

For the large ripple, could you please share the waveforms? It is skip mode at light load, so the ripple is larger than CCM.

For this device, it is internal compensation, if you add the Cff, a zero and a pole are introduced to the loop, so the frequency of the zero and pole should be appropriate.

Shawn

Hi, Thank you for your reply. The ripple voltage is about 1V. We can share the detail. But we want to send you the detail internally. Could you provide your e-mail address?

Best Regard,

tateo