TB67H420FTG Power Circuit

I recently purchased the TB67H420FTG board and it is working perfectly in a project I am building. As I am fairly new to electronics, I have been making a point of studying the schematics for the boards that I am using. Long story short, I was hoping to get some clarification on the power circuit and back EMF protection on the board.

The schematic shows that that the power circuit contains a Diode (D1) and something else (Q1). Searching for the symbol, makes me think it is a MOSFET, but I wasn’t sure. What is this component, and what purpose is it serving?


Q1 is a P-Channel MOSFET, and it is part of a reverse voltage protection circuit, similar to the one seen in this Hackaday article.


Hi Tony,

Thanks for the follow up. The article / were very informative. One follow up I have is whether this reverse voltage protection circuit also provides fly back protection, or should I put a separate diode across my motor when using this board?


The reverse voltage protection circuit on that motor driver carrier is there to minimize damage if you plug in your power input incorrectly, and is not the same as fly back protection. However, MOSFET-based drivers like the TB67H420FTG have built-in body diodes that act as flyback diodes, so there is no need to add external diodes. The diagrams on page 4 of the TB67H420FTG datasheet show the built-in diodes.


Thanks, Tony. Very clear now.