Teensy 3.6 DIY Reference Board schematic

[PhillipNash]

Hi there.

Paul has posted a reference board for the teensy 3.6 on Oshpark here https://www.oshpark.com/shared_projects/XbimUyLX and I would like to know where I can find the schematics for this please? I want to use this to learn more about the ARM processor and I want to use the reference board design for my own personal project

Thanks

[madmattd]

Paul has the schematics for all his boards posted on the store page, here.

[PhillipNash]

Thanks but I'm looking for the schematic for the reference board I.e. the eagle files. Would be nice to build upon the design.

[tenkai]

This is the schematic: https://www.pjrc.com/teensy/schematic.html

What you want is the PCB layout. I don't think Paul usually gives these out. If you are making a new project, its generally a good idea to start with a schematic and do your own layout to have a better understanding of what is going on. If you are proficient in the ECAD tool you are using, it shouldn't take you more than a day to replicate Paul's board, and if you are not proficient, its great practice to replicate the board from the schematics he provided

[Epyon]

Paul answered this question brilliantly here .

Anyway, Paul doesn't use Eagle, so don't expect any brd files other than the ones you make yourself.

[Eurotimmy]

May I ask on the DIY reference board where the VBAT pin is?
There's a couple of pins not screened on the DIY board and I'm yet to sit down and try to map anything out.

I'm new here and want to try my hand at getting this fabricated for me to reflow a board and play about with it.

[PaulStoffregen]

On the reference board, VBAT is shorted directly to VDD 3.3V. There isn't any easy way to access just VBAT on that board.

[Eurotimmy]

On the reference board, VBAT is shorted directly to VDD 3.3V.

Thank you Paul.
I don't suppose if I were to perform these changes before fabrication the board would behave properly?

1. Seperate VBAT from the 3.3V
(leaving the 3.3V to take its present path)

2. Add a 0.1uF capacitor, then

3. Add a 1A diode, out to a VBAT pin

As per the Teensy 3.6 schematic?
https://www.pjrc.com/teensy/schematic.html

[PaulStoffregen]

That would likely work. Seems likely you'd use 2 diodes, so you can connect a coin cell to the other diode.

[Zenbob]

Another Teensy 3.6 reference board question. The datasheet for the K66 does not specify crystal load capacitance in the table (in section 3.3.3). There's a footnote (1) that says internal capacitance is 20pf. And footnote (3) says you can use internal caps to achieve proper capacitance, which I assume Teensy 3.6 does as there are no external caps on the 16Mhz crystal.

I am confused about how to determine what would be a suitable crystal load capacitance for a Teensy 3.6/K66?

For our Teensy 3.2 based design, we used an Epson FA-20H 16.0000MF10Z-AJ0 16MHz ±10ppm, 8pF, 80 Ohms, which works great. Would the same one work?

[Zenbob]

Another Teensy 3.6 reference board question. The datasheet for the K66 does not specify crystal load capacitance in the table (in section 3.3.3). There's a footnote (1) that says internal capacitance is 20pf. And footnote (3) says you can use internal caps to achieve proper capacitance, which I assume Teensy 3.6 does as there are no external caps on the 16Mhz crystal.

I am confused about how to determine what would be a suitable crystal load capacitance for a Teensy 3.6/K66?

For our Teensy 3.2 based design, we used an Epson FA-20H 16.0000MF10Z-AJ0 16MHz ±10ppm, 8pF, 80 Ohms, which works great. Would the same one work?

I have found the answer... its on the MKL02 page

Also, an enlightening post in the archive by HWGuy.
https://forum.pjrc.com/archive/index.php/t-39801.html

HWGuy
12-10-2016, 08:21 PM
Here Paul recommends 20pF load capacitors for a 18pF crystal (Teensy 3.1): https://forum.pjrc.com/threads/27378-Teensy-3-x-Crystal?p=60672&viewfull=1#post60672

The 16MHz crystal on the Teensy 3.2, 3.5 and 3.6 has a load capacitance of 9pF.


For example the crystal (http://gr.mouser.com/ProductDetail/Epson-Timing/TSX-3225-160000MF09Z-AC3/?qs=sGAEpiMZZMsBj6bBr9Q9acukpafrIaZ1%2fpqCtYImzz0% 3d) wants;no additional load capacitors needed

Paul recommends a 12.5pF crystal for RTC (Teensy 3.0): https://forum.pjrc.com/threads/724-32-768-KHz-crystal-and-battery-for-Teensy-3-0-RTC-questions?p=1561&viewfull=1#post1561

https://i.imgur.com/4CfBLv9.png

the load capacitors are calculated with this formula

CX = 2 * CL - CPARA - CINT
19pF = 2 * 18pF - 7pF - 10pF


CX: external load capacitors
CL: crystal load capacitance
CINT: in microcontroller integrated capacitors
The Teensy core sets up the 16MHz crystal pins with a 10pF load: https://github.com/PaulStoffregen/cores/blob/master/teensy3/mk20dx128.c#L812
and the 32.768kHz crystal pins with a 20pF load: https://github.com/PaulStoffregen/cores/blob/master/teensy3/mk20dx128.c#L756
CPARA: Parasitical capacitance max 7pF

It would be good to add some specifics to the Oshpark Teensy 3.6 DIY Reference Board page. https://oshpark.com/shared_projects/XbimUyLX
Besides crystal specs, some other data points like, what USB connectors and SD socket fit on those footprints, and SMD passive sizes would be convenient.
That 5 pin 6x6 tactile switch looks like an Omron B3F-1105.

[Zenbob]

This is the schematic: https://www.pjrc.com/teensy/schematic.html

What you want is the PCB layout. I don't think Paul usually gives these out. If you are making a new project, its generally a good idea to start with a schematic and do your own layout to have a better understanding of what is going on. If you are proficient in the ECAD tool you are using, it shouldn't take you more than a day to replicate Paul's board, and if you are not proficient, its great practice to replicate the board from the schematics he provided

That's the schematic for the Teensy 3.6, not the ref board. The big difference is the pins on the K66 are numbered for BGA and not the LQFP that's on the ref board. Ref board uses MKL04 instead of MKL02 that's on the T3.6. Not sure what other differences there are, but that's what we'll have to figure out in order to make a T3.6 implementation on our own board.