Capacitors on VDDA and VREFH

[pozz]

I see two capacitors for VDDA and two capacitors for VREFH pins on TWR-K60N512. They are both X7R chip capacitors, 100nF and 10nF.

What is the reason to use two of them? Is it sufficient to use a single 100nF X7R capacitor near VDDA and VREFH pins of microcontroller?

[Dekiru]

They are bypass capacitors. They have different capacitance, ESR and ESL that help to eliminate the noise at different frequencies.

If you put only one, the noise at a frequency range may effects to working of the chip.

You can get more information if google with "bypass capacitor combination"

Regards