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TIC T834: USB powered stepper?

I have a very low power/low torque USB application for my TIC T834. My motor seems to do the job fine with the currently limit set to 96mA. Thus far, I’ve been working with a 5V, 1A supply, but the current is so low, I am wondering if I could run the whole thing off the USB port.

Could I run the 5Vout to the motor VIN? Is there a reason I shouldn’t try it?



I would not recommend using the 5V (out) pin from the Tic to power VIN or VM. The 5V output comes from a power selection circuit that can draw power from either the USB port or a regulator powered by VM, so connecting the 5V pin and VM creates a loop that might produce unstable behavior. Instead, you could try connecting VBUS (5V from the USB port) directly to VM. I have attached a picture that shows where you can access VBUS through an untented via.

By the way, I recommend looking at the supply voltage with an oscilloscope to make sure the motor and driver don’t cause excessive noise or voltage spikes, especially if you plan to power the system from a USB port on a computer.



I checked out the power supply on a scope and nothing seemed untoward, so I hooked up the VBUS like you suggested and it appears to be working great. Dropping the wall wart is awesome. Thanks!

BTW, I found a typo in the TIC documentation. It says the serial baud rate is at offset 0x06, but that would overlap it with another setting. Taking a look at the data there, I think it should be 0x05.

This is my first TIC, and I am really liking it.

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Thanks for pointing out that typo; we fixed it. I’m glad to hear you are having fun with your Tic. If you feel like sharing more about your application, we would love to hear about it!