TriFet Motor Driver

The TriFet is a 3-nMOS one direction motor driver rated for up to 60A of continuous current. This motor driver is perfect driving high-current solenoids, motors, small electric vehicles, and other high current switching applications. I have released this design as open-source hardware, feel free to modify and fabricate it yourself!

Design

The design of this motor driver is very simple, it consists of 3 N-type MOSFETs in parallel. I added ferrite beads to the gate of each FET to filter out any switching harmonics from the three parallel gates. I also added opposing diodes to the gate drive pin, which clamps the gate voltage to a safe range. There’s also a pulldown resistor on the gate so it doesn’t float, and an indicator LED on the PWM line just for fun. The motor output includes a flyback diode to prevent back-EMF from frying the driving circuitry.

Both sides of the board have an exposed plane which is connected to the MOT- net (the heat pad of the DPAK MOSFETs). In most cases, the FETs will be adequately cooled by this plane alone. For higher-current applications the PCB can be sandwiched between two pieces of aluminum heatsink with a bit of thermal paste.

I provided connectors for VIN, PWM input from a microcontroller, and motor output. Although the transistors only switch the motor’s negative supply, I routed the motor’s positive supply through the board for convenience.

Source

• Board Design: TriFet.brd
• Schematic: TriFet.sch
• Source Repository: http://protofusion.org/hg/TriFet

Feel free to leave a comment if you have any questions or ideas on how to improve this design!

About Ethan Zonca

Ethan is a computer engineer and open source hardware/software developer from Michigan. He enjoys AVR and linux development, photography, mountain biking, and drinking significant amounts of home-roasted coffee. Find out more at ethanzonca.com.