I found this development module datasheet for FTDI FT4232H chip: https://ftdichip.com/wp-content/uploads/2020/07/DS_FT4232H-56Q_Mini_Module.pdf At page 9, there is the module schematic, and there are two LC filters for VPLL and VPHY:


The inductors are marked "1K/0.8A", what value in H would "1K" indicate?


2 Answers 2


FB is "Ferrite Bead". One typical way to rate ferrite beads is the impedance at some reference frequency such as 100MHz and the allowable current.

Typically this impedance is lossy (resistive) so it is given in ohms. "1K" indicates 1k\$\Omega\$. At lower frequencies, the bead appears more inductive than resistive. The 0.8A is the rated current.

Here is a datasheet for an 0603 ferrite bead that likely meets the given requirements. From that datasheet, the complex impedance vs. frequency curves:

enter image description here

Sometimes other characteristics are important such as the DC resistance etc.


They’re ferrite beads with a 1k ohm impedance at (usually) 100MHz. They’re rated for 800mA.


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