Disclaimer - Build and/or use this at your own risk. I am not responsible for anything that arises from use of these files or documents, or for anything that arises from constructing and/or using this device.
Disclaimer 2 - the USB battery charging standard actually provides for a maximum of 1.5A, not 1A as originally believed. The polyfuse used (Littelfuse 1812L300MR) does not reliably trip below 5A, so this splitter may result in 4.5A maximum being drawn from the source. A planned Version 4 (which uses an 3A electronic fuse in place of the high-side switch to reliabily cut off current at around 3A) is being developed to address this issue. UPDATE August 19, 2024 - Version 4 does not work as the ENABLE pin logic for the electronic fuse was inverted. Version 5 is planned to fix this.
This is a USB-C splitter that splits a 5V 3A-capable USB-C power source to 3 5V 1A sources. This is for using a single-port USB-C PD charger to charge multiple 5V USB-C devices at once. Files are done in KiCAD 8, and manufacturing files for JLCPCB are provided. An enclosure design is included (which was designed in Autodesk Fusion 360) - .3mf, .step, and .f3z file are provided.
This design has been prototyped and tested.
With the widespread adoption of USB-C for device charging, I can now travel with a single compact 45W USB-C GaN charger and cable, and charge all my USB-C devices (phone, laptop, camera, flashlight, power bank, headphones, etc.) with that one charger. However, having a single cable and single charger is often limiting when I need to charge multiple devices, especially overnight, and many USB-C devices only need 5V and not many watts for overnight charging. This splitter goes onto an existing USB-C cable, for charging those devices simultaneously with a single charger, without needing a bulkier multi-port charger and multiple cables.
For safety, the splitter outputs only power on when the splitter is connected to a charger that indicates it can actually supply 3A, and includes a resettable fuse for overcurrent protection. The white LED lights up when it is connected to a powered USB-C cable. The green LED lights up if the power source is capable of supplying 5V 3A, and indicates the outputs have been powered on.
The outputs have D+ and D- shorted to indicate that they can supply ~~~1A~~~ 1.5A of current (per the USB Battery Charging standard).
The splitter only powers on with USB-C inputs capable of supplying 5V 3A. This is done by monitoring the USB-C CC lines and checking that the signal there is greater than 1.25V. Under the USB-PD standard, if the voltage on the CC pin is greater than 1.31V, it indicates the source is capable of supplying 5V 3A. Only then are the outputs powered on (as indicated by the green LED). Otherwise, the outputs are turned off.
The CC line voltage checking is done by a pair of comparators that monitor each of the 2 CC lines (as the USB-C input cable can be plugged in either way). The CC line voltage are compared against a 1.25V reference voltage (provided by an ST TS4061AICT-1.25 shunt diode reference) - a 1.31V voltage reference would have been more precise, but were not easily available, and 1.25V is above the 1.16V cutoff for a 1.5A source and works fine. The output of the comparators are fed through a pair of diodes (functioning as an OR gate) to the ENABLE input on an SiP32509 high-side switch that turns the outputs on and off. The device is over-current protected by a 3A resettable fuse (Littelfuse 1812L300MR). The CC lines and +5V bus are ESD protected with an SRV05-4 ESD diode array and an ESD5Z5V0 TVS diode.
Note that the output cables need 56K pull-up resistors between output CC and 5V to comply with the USB-C protocol - some devices may not charge if these resistors are missing. USB-A to USB-C cables are required to include this resistor, so using the USB-C end from a cut-up USB-A to C cable is recommended for the output cables.
A 3D-printed enclosure design is supplied in the Enclosure folder. The enclosure design is meant to be 3D-printed in two halves; on mine these were printed with translucent PETG to allow the indicator LEDs to shine through. The lower enclosure features embedded M3 nuts - the print must be paused at the appropriate layer and M3 nuts need to be inserted before the print resumes. The two halves are screwed together with M3x8 countersunk screws. The enclosure is designed to use Ikea SITTBRUNN USB-A to USB-C cables, as these are widely available and inexpensive. The ends are wrapped in Qualtek Q5-3X-3/16-01-QB48IN-25 adhesive heatshrink for strain relief. To dissipate heat from the SiP32509 high-side switch (U2), which is expected to generate about 0.4W of heat at 3A, either the enclosure must be potted to facilitate heat transfer, or a thermal pad must be used between the SiP32509 and the case. Lower-enclosure-potted has a small hole to inject potting compound (or hot glue, or silicone) into the case - use a high viscosity potting compound to avoid it getting in the input USB-C connector. Lower-enclosure-thermal-pad has a small raised feature above the SiP32509 IC to place a 1.5mm thick thermal pad between it and the case.
| Description | Quantity | Notes |
|---|---|---|
| PCB | 1 | See "Ordering the PCB" section below |
| Upper enclosure | 1 | FDM 3D-printed |
| Lower enclosure (thermal pad or potted) | 1 | FDM 3D-printed. Has 4 embedded M3 nuts, which must be installed while 3D printing |
The 3D-printed parts were FDM 3D-printed in PETG, though other materials probably work fine here. A translucent or semi-translucent material is recommended so that the indicator LEDs can shine through.
| Description | Part number | Quantity | Notes |
|---|---|---|---|
| Ikea Sittbrunn USB-A to USB-C cable | Ikea 805.394.83 | 3 | |
| M3 hex nut, DIN 934, zinc-plated steel | McMaster-Carr 90591A250 | 4 | Generic. Not stainless steel to avoid galling |
| M3x8 flat head screw, DIN 7991 / ISO 10642, hex drive, 18-8 stainless steel | McMaster-Carr 92125A128 | 4 | Generic |
| Adhesive-lined heat-shrink, 3/16" / 4.8mm ID, 3:1 shrink ratio | Qualtek Qualtek Q5-3X-3/16-01-QB48IN-25 | 3x 25mm |
If you are using the thermal pad option for the lower enclosure, you will need 1.5mm thick thermal pads. I used Thermalright Extreme Odyssey 1.5mm pads for the ones I have built, but other 1.5mm thermal pads (e.g. Arctic TP-3) may work. The thermal pad must not be electrically conductive.
If you are using the potted option for the lower enclosure, you will need some sort of potting compound that can be injected through a 5mm diameter hole. The ones I built used hot glue. Make sure the potting compound has high enough viscosity to not get into the input USB-C port.
The PCB can be ordered from JLCPCB in China, and the files are provided in their format.
1.) Go to JLCPCB, and press "Order Now".
2.) Next, you want to upload the Gerber ZIP file for the PCB.
3.) Specify the following options once the Gerber file has uploaded. Non-default settings are highlighted in red.
For color, specify a color supported by JLCPCB's "Economic PCB Assembly". As of June 30, 2024, green, black, blue, red, white, and purple are supported. Note that some colors might incur an extra fee.
4.) Under "PCB Assembly", specify the following options:
5.) Press "Next":
6.) Upload the BOM and CPL files:
7.) Confirm the components in the next page. If any components are listed as "Shortfall", JLCPCB does not have enough of them in stock and will not install them on any PCBs. You will have to purchase them from and solder them on yourself. Alternatively, you can wait for JLCPCB to restock the part.
8.) Next is the component placement confirmation page. You should not have to change anything here:
9.) You will need to describe the item in the next page for customs purposes. As of June 30th, 2024, I could not find an option most suitable for this, so select "Office Appliances and Accessories > Others" in the options, and type in "USB cable splitter PCB".
| Tool | Purpose |
|---|---|
| Flush cutters | Stripping wires, trimming leads |
| Soldering iron | Soldering the USB-C output cables to the PCB |
| Solder | You need it to solder |
| Flux | Makes tinning the output cables easier |
| Heat gun | For the heat-shrink strain relief |
| Wire strippers | For stripping wire |
If you are using the thermal pad option for the lower case, you will need scissors to cut the thermal pad. If you are using the potted option, you will need potting compound and whatever tools needed to inject into the hole in the case.
1.) Test the PCB by plugging in a 5V 3A-capable USB-C source. When plugged in, both the white and green LEDs should light up. Next, test it with a non-5V 3A capable source (e.g. use a USB-A cable). When plugged in, only the white LED should light up.
2.) Unplug the PCB.
3.) Take the Ikea Sittbrunn USB-A to USB-C cable, and cut the USB-C end to about 20-30mm longer than the desired length.
4.) Strip about 20mm off the outer insulation. The method I found works well is to use a pair of flush cutters to "bite' the insulation parallel to the cable, and then cut the resulting pieces off. After stripping, check that the insulation for the individual wires are not damaged.
5.) Strip about 10mm off the inner insulation for one of the wires.
6.) Wind the strands tightly with your hands.
7.) Apply some flux to the stripped wire.
8.) Tin the wire with a little bit of solder. Try to add enough solder here that the strands don't come apart, but not so much that the stranded wires no longer fit in the output footprint through-holes in the PCB.
9.) Repeat Steps 5 through 8 for the remaining wires. This is best done one wire at a time to prevent the wires from becoming unstranded from bumping into each other.
10.) Cut some pieces of heat-shrink that are 20-30mm long:
11.) Put the heat shrink through the cable.
12.) Solder the wires to one of the three output footprints, and trim off any excess using the flush cutters.
The following wire colors correspond to the following pins, which are labelled on the underside of the PCB:
| Color | Pin |
|---|---|
| Black | GND |
| Green | D- |
| White | D+ |
| Red | +5V |
Check that the strands from each wire are not shorted to each other. However, since D+ and D- are shorted to each other on the PCB per the USB Battery Charging standard, it does not matter if those two specific wires are shorted to each other.
13.) Repeat steps 3-12 for the remaining outputs. Remember to slip the heatshrink tubing on before soldering. Double check that wires are not shorted to each other.
14.) Plug the PCB into the 5V 3A USB-C source again. Check that the green and the white lights both light up. If not, you may have a short circuit somewhere.
15.) Move the heatshrink tubing down the cables, like so:
17.) Using a heatgun, shrink the heatshrink:
18.) (For the thermal pad variant only) - Cut a piece of thermal pad to about the size and shape of the raised portion marked in red, and place it on there:
19.) Place the PCB and the soldered wires onto the lower enclosure like so:
20.) Place the upper enclosure on, and attach it with the 4 M3x8 flat head screws.
21.) Test the splitter by plugging it into the 5V 3A source again, and using it to charge various devices (e.g. a phone). Make sure each output works. If not, check your soldering.
22.) (For the potted variant only) - Inject potting compound into the 5mm hole on the lower enclosure, and it let it dry/solidify/cure.
You are done!