Very Hot Driver Chip, but motor current is in limits


I just purchased 10 of the TB67S128FTG Stepper Motor Driver Carrier to operate these steppers with the following specifications:

Amps: 1.5A/phase
Resistance: 1.6 ohms
Inductance 3mh

I adjusted the driver for a motor current to 1.5A ( using an ammeter in series with the motor winding ) in full step as suggested, I’m using a 24VDC supply.

At that motor current, the current draw for the 24 volt supply is .66A indicating a power supply dissipation of 15.84 watts ( 24V * .66A ).

The motor is dissipating 7.2 watts ( 2 windings * 1.6A^2 * 1.5R ohm’s law ) leaving 8.64 watts being dissipated in the chip.

The chip is indeed getting very hot immediately, though it does run the motor fine, though I don’t keep it on long.

I am concerned that the chip is dissipating far too much power since the spec sheet says maximum dissipation in the chip is 1.5 watts.

I find no limitation with respect to motor resistance or inductance in the TB67S128FTG Stepper Motor Driver spec sheet.

I would appreciate any suggestions, thank you very much.


It is normal for our TB67S128FTG Stepper Motor Driver Carrier to get very hot while operating, but something about your numbers does not seem right. The specifications for your motor that you posted do not match the specifications in your link, but either way 0.66A seems high for a 24V supply given the motor’s rated voltage is an order of magnitude lower than that. Could you tell us more about your setup? What is your power supply? What voltage do you measure on VREF? Do you have anything connected to the GAIN_SEL pin? Could you post pictures of your setup that show all connections?


Thank you Claire, I’m going to test your 36v4 driver with this motor and use that if it seems better for my application If not, I’ll document my setup and measurements of the TB67S128FTG driver more thoroughly as you suggest and post it.

Hi Claire,

The 36v4 board works great in the setup and runs cool, even at 24 volt supply and 2.0 amp motor current. I used your excellent Arduino example for testing which was very useful. I will request to return the 9 unused TB67S128FTG boards and apply them as credit for the 36v4, I prefer the safety factor anyway of not being near its limits.

I’m glad you found a solution that seems to work for you. It is not surprising that our High-Power Stepper Motor Driver 36v4 runs cooler than the TB67S128FTG carrier since it is rated to handle twice the current. We haven’t received an email from you yet, so just so there is no confusion, any return or exchange requests should be made via email.