D1 is now a B140, which is a MacroFab house part. It's actually a bit
more expensive from distributors than the SS14FL, but the lack of a
labor charge makes it quite a bit cheaper for PCBA. It's also larger,
so in order to fit the new part, I moved it between Q2 and J1. This is
possible because…
Q2 is now a DMP3017SFG. This is a cheaper, smaller, and less
over-specified MOSFET which should be fine for the job of controlling
the PD Buddy Sink's output. It uses a proprietary Diodes Inc. package
whose footprint I contributed to KiCad's library. Because the new
MOSFET is so much smaller than the old one, I was able to fit it close
to the board edge where R9 used to be.
The whole output circuit has been rearranged, and I like its layout a
lot more now. Also, the new position of D1 allowed me to move a bunch
of reference designators closer to their footprints, which is nice.
It used to be an MMBT2222, now it's an MMBT3904. The new transistor is
slightly lower-spec'd, but is still more than plenty for this
application. Also, it's a MacroFab house part, so the boards will be
even cheaper to manufacture.
Assuming I'm going to keep ordering boards from MacroFab, it makes sense
to use their house parts as much as possible. Therefore, the next
boards will use a C&K PTS810 as the Setup switch instead of an Alps
SKQG. In addition to saving money, this change allows room for larger
"Setup" and "GND" labels.
With the VBUS symbol merged into the KiCad library, I no longer need to
use my own. This commit changes the schematic to use the standard VBUS
symbol rather than a custom one.
The SOT-89 footprint changed its name slightly in the KiCad library,
so the voltage regulator has been updated accordingly. It has a nice
new 3D model too. It's not weird and blue anymore. I like it.
The SOD-123 was also updated to have a 3D model. The board now only
lacks models for the footprints I made myself. Heh.
The footprints haven't been merged yet, but the symbol has. Therefore,
I updated the footprint in the pd-buddy library to match the new symbol
(changed shield pin number to S1) and changed the schematic to have the
new connector symbol. The board looks the same except that a couple
references changed.
Now that the appropriate pull requests have been merged, I can use the
standard part rather than the one I created in this repository.
Speaking of which, this commit removes FUSB302B and MLP-14 from this
repository.
This is a major change! Almost all the components have changed to
smaller versions, with 0603 and 0402 passives and a QFN microcontroller.
The board now has four layers, with internal layers used for VBUS and
GND. The board now measures a mere 25×30 mm! The SWD header and Boot
switch footprints have been moved to the bottom to help with this
shrinkage. Two test points were added to the bottom as well to make it
possible to power the board without using the USB connector. The
mounting holes are now slightly smaller (better sized for M3), and only
17 mm apart instead of the old 18 mm.
To sum up, everything is smaller and that's almost entirely a good
thing, except now it's not really possible to build one by hand.
There's now quite a bit of stuff located under the USB connector. A lot
of manufacturers mark that area as a keep-out zone, but luckily,
Amphenol is not one of them.
Boy, I'm good at messing up transistors! This time it was just the pin
numbers for the collector and emitter reversed, because I didn't copy
the symbol from the datasheet but rather assumed another SMT 2222 would
have the same pinout. Interestingly, it actually was able to control
the MOSFET at VBUS = 5 V and at VBUS = 9 V, but at VBUS = 15 V the
reversed transistor couldn't pull the MOSFET gate down enough.
Clara Hobbs