When one looks at common mode chokes for USB 2.0 applications choke manufacturers always recommend CMC with a common mode impedance of 90 ohms @ 100 MHz.
How does this relate to
- USB 2.0 differential impedance of 90 ohms (& 45 ohm single ended impedance)
- the "Hi-Speed" data rate of 480 MBit/s (respectively a frequency of 240 MHz)
- an approximate USB 2.0 bandwidth of ~1200 MHz (5 x 240 MHz)
Why aren't they made for, say 90 ohm @ 240 MHz? Why are they trimmed for 90 ohm @ 100MHz? Couldn't chokes with values that differ from this 90 ohm @ 100 MHz be used as well? What are the determining factors here?
Sorry the question may seem a bit weird but I couldn't quite get that topic. Maybe someone can shed some light on this.