I saw these on AliExpress and thought
they are tiny. I must get some. And they
are really very small. The PCB is barely
wider than the USBC socket and slightly
shorter. It’s only 10 mm by 6 mm. So,
what does it do? It’s a USBC single cell
lithium battery charger. So, let’s have
a look at the PCB and the schematic. We
have the standard 5.1K resistors
connected to the CC lines of the USBC
port. This tells whatever is on the
other end that we want to receive power.
These are really important. Without
them, a lot of power banks just won’t
give you any juice. The main chip is the
LP 4054. This is a linear lithium ion
battery charger. We’ve got a couple of
decoupling capacitors on the 5V supply
and another couple on the battery side
of things. The fueling resistor is
1.65K.
This gives us around 600 milliamp. This
matches up with what we see with the USB
power meter when charging a flat battery
around 600 milliamps being drawn. As the
battery charges, this does decrease.
There are two indicator LEDs, a red one
that indicates charging and a green one
that lights up when the battery is fully
charged. This is a pretty interesting
circuit. There is only one pin to
indicate charge status on the IC, and
this is pulled low during charging. This
causes the red LED to light up and keeps
the green LED unlit. When the battery is
charged, it goes into high impedance.
This allows current to flow through the
green LED as well as the red LED. The
red LED will still glow dimly, but
because green LEDs are so much more
efficient, the green LED lights up quite
brightly. Now, one thing to be careful
of is that these linear battery chargers
get quite warm during charging. They
need to dissipate any power that is not
going into the battery, and they do this
as heat. Looking at the board through my
thermal camera, the temperature seems to
top out at around 92 or 93°. So, that’s
not too bad, but just be careful how you
arrange things. You probably don’t want
the battery to be sat right on top of
the PCB. Anyway, it’s a nice compact
design. Let’s try and recreate it. So,
before we jump into PCB way, let’s do a
quick shout out to the Patreons and also
to PCB way. I’ve got some PCBs with them
right now. Check out the link in the
description. So I’m over in Keycad and
here’s all our components. I hidden the
references because they were just
getting in the way. Now what I’ve done
is I’ve imported the design rules for
PCB way and that’s also imported a whole
bunch of um standard nets. So if we look
at this got some power nets and if we
look at the predefined sizes we got all
of these. Now PCB way do recommend
sticking to a minimum 0.15 mm. So that’s
600 mil. So, we’ll try and do that. And
we’ll use larger traces for any power
lines. So, let’s create our um our edge
cuts. So, I’ll go over to edge cuts and
we’ll just create a quick rectangle.
And then we’ll set the size for this.
So, we want 10x six.
So, it is a pretty small PCB. So, let’s
start arranging stuff. We’ll do what
they’ve done and we’ll flip this over to
the bottom side. So, let’s move our USB
C connector into place. So, it looks
like we can place it just around about
there. Um, we will chop off some of
this, but that’s probably okay. So, what
else do we need? So, here’s our charging
IC. So, let’s position this in a
sensible place.
And then we have our two LEDs for
indicating the status along with their
um current limiting resistors. So, let’s
put these up the top just like in the
board that we have. So,
arrange those there. And this needs to
Yep. That’s correct.
Let’s put them in the middle.
And then we have their current limiting
resistors. I think that’s one of them.
Put that there. And this is probably the
other one. Yeah. So, that can go there.
So that’s our top part of the board
pretty much arranged. Um let’s just
align these so they look nice.
So we’ll just do align align to top and
then we’ll just um distribute them
horizontally.
Okay. So that’s nicely laid out laid out
at the top. Here’s our two pads for the
battery. Um now I wonder which way
around we should put this IC. Let’s try
doing it this way round. So, battery
plus is on the left. So, let’s move our
battery plus pad
down to here. And then our ground pad
can go over here.
So, that’s those positioned. Now, we
have a bunch of components here. Let’s
just move them closer so we’re not
jumping around so much.
So, here we have
various resistors. So, here’s one. This
is the USB CC one. We can put that
there. And this is decoupling capacitor
for the battery. So, we’ll put that
there.
And this one, that’s the other CC line
for the USB. So, that can go there.
That’s nicely arranged. Now, here’s our
two 5V decoupling capacitors. They live
over here.
Now we’ll move those nicely together.
And then we have the programming
resistor which is this one. So that goes
over there.
And then we have another decoupling
capacitor for the battery. So let’s just
stick that next to that one. So now we
can just wire this up. So let’s do the
5V first. So hopefully if I’ve set my
nets up correctly,
I should get for the 5 volt, we should
get this power one net class, which will
be 0, no, 0.3 mm. So that should be
reasonably large, can carry a sensible
amount of current. So let’s go here and
start doing some routing. So we need a a
vire to come back up that can go there.
And then we’ll um we’ll route from here
as well. go around the top.
There we go. So that’s um that’s 5 volts
the power supply. Uh let’s do the
battery as well. So switch the top
layer. So here’s our battery that can go
there and then straight to there. Just
flip this around. So that’s nicely wired
up as well. Um so let’s do the USB.
Actually, let’s do these ones at the
top. So these can be fairly thin. They
pretty much can’t. So they just go like
that. And interestingly, oh my 5 volts
actually. So
this LED is the charging one. This is
the not charging. So let’s actually flip
those around completely.
Nice. And then our 5V is in the right
place to actually connect to our 5V. So
let’s hook up that in. And then our 5
volts. Let’s do a via. And then that can
connect straight to there. Switch back
to the top layer. Let’s hook up our
decoupling capacitors for the 5 volts as
well.
So that’s the decoupling done. Let’s do
our USB lines. So these CC ones need to
be hooked up. So we’ll have to
use a via drop back down and then do the
same here.
So that’s wired up. Uh what’s left? So
we got our 5 volts there. Oh yeah. So
the charging indicator. So that’s this
one hooks into there. Let’s just wire up
all the grounds so that we definitely
know they’re connected. So do ground to
there. The ground round to there. We’ll
connect that ground to that ground. That
ground to that ground. Ground to there.
Let’s do another one round to there. And
we need one from there to there. And
this ground here also needs a
connection. So let’s do let’s do that.
Actually, let’s make that thicker. So
can we fit
a.3 mm trace from this ground? Yes, we
can. So that will go to a nice wire as
well. Maybe we can do on on the other
side too. So I’m going to put a ground
paw all over this. So we’ll do that now.
And let’s see how that comes out.
So, put it on the top and the bottom
layers. It’s going to be ground. Hit.
Okay,
talk to T
talk.
And let’s get rid of this um this
reference. Don’t need that. Okay. So,
let’s also let’s wire up these grounds
explicitly.
So, they are all wired up. And let’s do
big fat traces between these actually.
So, I delete those.
Come on. Give me a big fat trace.
It doesn’t want to. Come on.
Sometimes Keycad is a bit annoying. Oh,
there we go. Big fat traces. Yes, that’s
exactly what we need.
Okay. Oh, we need to wire these grounds
up. Otherwise, our decoupling capacitors
are not going to work. That’s those
wired up as well. So, took those there.
And we can put some wires in just to
link together our ground planes nicely.
Okay. Let’s run a DLC check and see if
it actually would work.
So run DRC for all those. So nothing
unconnected. Um thermal relief thermal
relief via diameter.
I think that’s a minor thing. We can fix
that just in the in the setup of the
vires. Slightly the wrong size. Um but
apart from that, done. Let’s see what it
actually looks like. Let’s use the 3D
viewer and see if we’ve recreated the um
PCBs from AliExpress.
And yeah, it looks pretty good. Not bad
at all. So there you go. Um pretty
simple circuit really. So here’s our
battery connectors. We should label
those. Let’s put some silk screen on. So
go back here. Use the um front silk
screen. Okay. What do we need to do?
plus.
So there’s our plus. Let’s just move
that over there. And we need a minus. So
we’ll put that over there.
Minus. Okay. Let’s just move it out of
the way of those resistors.
Okay. And move it in a bit as well. And
let’s just adjust this one slightly.
Cool. Okie dokie. You can tidy this up
quite a bit. Um, we don’t need all this
silk screen really. Um, but let’s have
another check and see how it looks. You
know, there’s our plus and our minus for
the battery. Um, yeah, it’s pretty neat.
Not bad. I made a good effort. Not bad
at all.