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BoostCore-Module

BoostCore-Module is a compact adjustable DC-DC step-up boost converter module built around the MT3608 regulator.
It supports USB-C 5V input, an optional external VIN input, Schottky OR-ing input selection, resettable fuse protection, TVS protection on USB VBUS, and a trimpot-adjustable output feedback network.

PCB manufacturing sponsor: This project is sponsored by PCBWay.
PCBWay support is mentioned in the documentation because the PCB is intended to be published as an open hardware project and manufactured as a compact prototype board.

Project Highlights

MT3608 based boost converter
USB-C power-only input
External VIN input
Input OR-ing with SS36 Schottky diodes
USB-C VBUS protection with 5V TVS diode
USB-C PTC fuse protection
Optional VIN_EXT PTC fuse protection
Adjustable output voltage using trimpot
0805 resistor/LED-friendly design choices
Test points for VIN, VOUT, FB, EN and GND
KiCad-ready hardware folder structure
GitHub documentation package with BOM, assembly, layout and testing guides

Sponsorship

This project is sponsored by PCBWay.

PCBWay is mentioned here as the PCB manufacturing sponsor for the open hardware release of BoostCore-Module. The board was designed with prototype manufacturing in mind, including compact routing, silkscreen labels, test points, and an export-ready project structure.

Electrical Overview

Parameter	Value
Controller IC	MT3608
Topology	Boost / step-up
USB-C input	5V only
External VIN input	2V-24V target range
Output voltage	Adjustable by RV1 trimpot
Switching frequency	MT3608 typical 1.2MHz
Inductor	4.7uH recommended
Main boost diode	SS36, 3A, 60V
Output adjustment	R1 + R2 + RV1 feedback network
Output capacitor caution	Use 50V capacitors for high output voltage

Current Feedback Network

The adjustable output stage is:

VOUT -> R2 10k -> RV1 100k trimpot -> FB -> R1 2.2k -> GND

Recommended trimpot wiring:

RV1 pin 3 -> R2 side
RV1 pin 1 + pin 2 -> FB node

Formula:

VOUT = 0.6 x (1 + R_UPPER / R1)

Where:

R_UPPER = R2 + active RV1 resistance
R1 = 2.2k

Important:

Start with the trimpot at the lowest output setting.
Always adjust output using a multimeter.
Do not connect a sensitive load before confirming VOUT.
High output voltages require output capacitors rated above the selected voltage.

Images

Layout preview

PCB layout PCB layout 1 PCB layout 2

Important Hardware Notes

USB-C input

The USB-C connector is used as a 5V power-only input.

Required CC resistors:

CC1 -> 5.1k -> GND
CC2 -> 5.1k -> GND

USB-PD negotiation is not implemented. The USB-C input is therefore 5V only.

F1 USB fuse

Current selected part:

F1 = KLM3S300RY
PTC resettable fuse
1206 / 3A / 6V
USB-C 5V input only

Do not use this part on the 24V external input path.

F2 external VIN fuse

Compact option:

F2 = MF-MSMF110/24X-2
1812 / 1.1A / 24V

Higher-current but larger option:

F2_ALT = FSMD185-2920-R
2920 / 1.85A / 33V

D2 USB TVS

D2 must be a 5V TVS diode, not a Schottky diode.

Recommended:

D2 = P4SMAJ5.0_R1_00001

D1 / D3 / D4

The board uses SS36 diodes:

D1 = SS36
D3 = SS36
D4 = SS36

D3 and D4 are used for input OR-ing.

C4 polarity

If using the compact electrolytic output capacitor:

C4 (+) -> VOUT
C4 (-) -> GND

Mark polarity clearly on silkscreen.

PCB Layout Rules

Boost converters are layout-sensitive. Follow these rules:

Keep the SW node as short and small as possible.
The SW node is:
```
U1 pin 1 SW + L1 right side + D1 anode
```
Do not place copper pour under the SW node area.
Keep FB trace away from SW node, diode switching node and inductor.
Place C1 close to U1 IN and GND.
Place output capacitors close to D1 cathode and GND.
Use a solid GND plane on the bottom layer.
Add via stitching near high-current GND return paths.
Do not route feedback under the inductor.
Make VIN_SYS and VOUT traces wide.

Assembly Order

Recommended assembly sequence:

Inspect PCB visually.
Solder USB-C connector.
Solder protection parts: F1, D2, D3, D4.
Solder MT3608.
Solder inductor L1 and diode D1.
Solder resistors and small capacitors.
Solder RV1 trimpot.
Solder output capacitors.
Solder connectors.
Inspect polarity of C4.
Check shorts between VIN, VOUT and GND.
Power on without load.
Adjust output voltage with a multimeter.
Test with a dummy load.

First Power-Up Checklist

Before applying power:

Check USB-C VBUS is not shorted to GND.
Check VIN_SYS is not shorted to GND.
Check VOUT is not shorted to GND.
Confirm D1 cathode points to VOUT.
Confirm C4 polarity.
Confirm RV1 pin 1+2 go to FB.
Confirm RV1 pin 3 goes to R2.
Confirm EN is pulled to VIN_SYS through R6.

Initial test:

1. Apply input power.
2. Measure VIN_SYS.
3. Measure VOUT.
4. Adjust RV1 slowly.
5. Verify output under light load.
6. Check temperature of MT3608, L1 and D1.

License

Released as open hardware documentation. See LICENSE.

Disclaimer

This is an open hardware project. Use at your own risk. Verify all footprints, ratings, clearances, capacitor voltage ratings and component stock before fabrication or ordering.

BoostCore Module