I'm making a USB host using the Teensy 4.0 and I think I've worked out details, but have a few lingering questions I'm making educated guesses about.
I'm using a PTC fuse, a TVS diode and 100uF between the 5V that powers the Teensy and VBUS and TVS diodes on the D+ and D- lines
1) Is there no need for any termination resistors in series with the D+ D- lines?
2) Any need for common mode chokes in series with the D+ D- lines? I see some USB designs don't bother with chokes or beads or termination, but others do.
3) I have the same question regarding adding bead in series on the VBUS after the fuse. And if a bead is recommended, what frequency would we be filtering. Is there a recommended inductance?
4) Any advantage to using a current limiting switch vs a resettable PTC fuse on VBUS IF that IC switch is high by default anyway? Perhaps an advantage to having this switch turn on AFTER the Teensy boots up rather than when the 5v on the main board turns on?
5) Was there a connection scheme in mind when putting these where they are on the bottom side with SMT pads?
Working on connecting D+ D- using right angle header soldered to the SMT pads. We'll see how that works out. A tiny flexible cable is still possible.
Thanks for any thoughts and advice.
I'm using a PTC fuse, a TVS diode and 100uF between the 5V that powers the Teensy and VBUS and TVS diodes on the D+ and D- lines
1) Is there no need for any termination resistors in series with the D+ D- lines?
2) Any need for common mode chokes in series with the D+ D- lines? I see some USB designs don't bother with chokes or beads or termination, but others do.
3) I have the same question regarding adding bead in series on the VBUS after the fuse. And if a bead is recommended, what frequency would we be filtering. Is there a recommended inductance?
4) Any advantage to using a current limiting switch vs a resettable PTC fuse on VBUS IF that IC switch is high by default anyway? Perhaps an advantage to having this switch turn on AFTER the Teensy boots up rather than when the 5v on the main board turns on?
5) Was there a connection scheme in mind when putting these where they are on the bottom side with SMT pads?
Working on connecting D+ D- using right angle header soldered to the SMT pads. We'll see how that works out. A tiny flexible cable is still possible.
Thanks for any thoughts and advice.