Im looking at the teensy schematic and it says that the usb_vbus inputs are not required. So to make sure im reading this corectly for a board im working on I can just feed my regulateded 3v3 output into VDD_SNVS_IN and that should be fine to kickstart the process? Also it shows the rating for the inductore on L1 but i am unsure what l# is supposed to be. What is Ferrite 120 supposed to mean? Is it like a ferrite inductor then 120 of what measurement? Thanks for the help if given . . .
Help With Teensy Schematic General Questions
- Thread starter anatoledp
- Start date
PaulStoffregen
Well-known member
Ferrite bead inductors are almost always rated as ohms at 100 MHz. They rarely have an actual inductance spec. So 120 means 120 ohms at 100 MHz. They also usually have a max current spec, so you'll want to choose one with high enough current for the RT1062 chip (approx 100mA) plus all the other circuitry you board will have.
Just search for ferrite at any electronic parts site like Digikey. When you see how ferrite bead parts described, it'll probably make much more sense.
Just search for ferrite at any electronic parts site like Digikey. When you see how ferrite bead parts described, it'll probably make much more sense.
allright thanks for that . . . did a little more research and man can they be valuable it seems for ringing. On the other topic i can just feed 3v3 into VDD_SNVS_IN right? since by the time the internal regulator powers up it is already feeding the voltage back into the system?
PaulStoffregen
Well-known member
For your 3V3 question, I'd recommend reading the Power Up Sequence on the T4 bootloader page, and maybe also NXP's hardware design guide which you can find on their website.
Specifically about "i can just feed 3v3 into VDD_SNVS_IN right?", the answer would be "it depends" on what other connections exist between 3V3 and any other pins on the RT1062 chip.
Specifically about "i can just feed 3v3 into VDD_SNVS_IN right?", the answer would be "it depends" on what other connections exist between 3V3 and any other pins on the RT1062 chip.
This would without anything any between. As in a direct power line and only that. I was asking because in the startup guide it mentions that 1.1v or something around is initially fed into SNVS_IN and then later after the rest of the stuff happens it gets changed to 3.3v. so I didn't know if there was some sort of logic that first expects the lower voltage or if it will just regulate the same from the beginning
Checkout the "Power Up Sequence" on the bootloader page Paul linked to and walk through the steps (use the buttons to help you visualize) until you understand the flow. I would try to add more information here, but I don't think I can do it more clearly/succinctly than it already is on that page.