DS90UB947-Q1EVM: Ferrite Bead and Capacitors Selection

Carlo

Part Number: DS90UB947-Q1EVM
Other Parts Discussed in Thread: DS90UB947-Q1,

Hi E2E,

Good day.

In the DS90UB947-Q1EVM user's guide, there are several ferrite beads and capacitors implemented in the power pins of the DS90UB947-Q1. Do we have any design guidelines or calculation tool in selecting the appropriate ferrite beads and capacitors? Why is the1.1V supply pins are connected to Z=120ohm@100MHz ferrite beads while the 1.8 supply pins are connected to Z=1Kohm@100MHz ferrite beads.

Thank you in advance for your help.

Regards,
Carlo

over 5 years ago

0 Liban Hussein1 over 5 years ago

TI__Prodigy 460 points

Hello Carlo,

I'll answer your question in two parts.

a.) The recommended values for the capacitors and ferrite beads are the values mentioned in the datasheet and the EVM reference schematics.

b.) As the DC bias current increases, the ferrite bead inductance decreases due to saturation effects on its ferrite core. From this, we can see that for the 1.1 V supply, the DC current is rated at 3A, while for the 1.8 supply, it’s rated at 800mA. This is why the 1.8 has a greater impedance at the same frequency. These ferrite beads are what we have found to work best for these voltages for noise filtering.

1.8V- https://www.mouser.com/ProductDetail/TDK/MPZ1608S102A?qs=5GteYzHiykYc7hBaAxyqRA%3D%3D

1.1- https://www.mouser.com/ProductDetail/Murata-Electronics/BLM18SG121TN1D?qs=OMB6gcCnelWdy%252B7xRA0fBw%3D%3D

Best,

Liban H.

Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

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DS90UB947-Q1EVM: Ferrite Bead and Capacitors Selection