I am very fond of the TB6612 dual motor driver board. Often I see reference to the need for flyback diodes, but -just as often - the subject is ignored. Are there times when this board will need the 8 diodes? Is the requirement related to motor current or supply voltage? Thanks!
Hi.
Flyback diodes are generally needed when controlling motors to prevent voltage spikes when power is removed from the motor (which is an inductive load). However, newer MOSFET based drivers, like the TB6612FNG, have built-in body diodes that act as flyback diodes, so there is no need to add external diodes. The diagrams on pages 3 and 4 of the TB6612FNG datasheet show the built-in diodes. The references you saw to needing external flyback diodes might have been referring to BJT based H-bridges.
-Claire
Hi.
I agree that the newer mosfets have built-in body diodes and much lower on resistance which is especially important with smaller robots and lower voltage power sources. I have, however, read that the body diodes are not really built to handle the power surges created by low cost hobby motors. Have you folks ever done any extensive testing to determine if the built-in diodes actually are large enough to handle external surges? I guess I’ll do my own testing, but I am looking for external input.
Thanks, Jim.
Can you let us know where you read that? We have not done testing specifically for that, but we have used and sold hundreds of thousands of drivers like these without external diodes without notable issues.
-Claire