AM3356: Ferrite Bead Requirement for AM3356 Power

Hi Eby,

There are a few good threads on E2E with this same question, and the consensus has been ferrite beads are not strictly required on the I/O supplies.  If you search "AM335x ferrite bead", you will find these threads.

It is important to include ferrite beads on the analog supplies (you didn't ask this, but wanted to be sure this was clear).

Regards,
Mike

Inserting ferrite beads in the path of power supply connections is an effective way of increasing power supply noise rejection between power rails. However, it is very important that you place appropriate decoupling capacitors between each ferrite bead and associated processor power pins. Once you insert the ferrite bead, the processor power pins are effectively isolated from your low impedance power distribution network (PDN), so local decoupling capacitors must act as the low impedance power source that is able to accommodate worst case power supply transient currents. Therefore, you should verify each isolated power rail in your system remains within the recommended operating conditions under worst case operating conditions. You also need to confirm these isolated supplies never develop a resonance due to the combination of current transient frequency and the natural resonance of ferrite bead and decoupling capacitors.

Regards,
Paul