24v21 Motor Driver failure

I have previously purchased two 24v21 motor drivers which are working well. I purchased a third and it appears to be non-functioning from day one.

The driver in question has never been used to actually power a motor. As soon as I connect VIN and GND without any load or any pins connected to the control side the board immediately gets hot. Based on feel it seems the small square SMD chip next to the CS and FLT pins is what is getting hot. Don’t know the temperature but it is in the “uncomfortable but doesn’t burn your finger range”.

A multi-meter on OUTA OUTB reads 0 volts at all times. I have tried applying HI and LOW signals to the PWM and DIR pins and OUTA OUTB reads 0 volts.

Any thoughts? Did it get fried? ESD?


Could you post some close-up pictures of both sides of the board, as well as pictures of your setup that show all of your connections? Did you ever have anything else connected to the board? What is the voltage on the 3V3 (out) pin, and has anything been connected to that? Please note that shorting the 3V3 (out) pin to the neighboring VM pin while the board is powered will instantly damage the board, so be careful while measuring it.


The only thing I have connected to the OUTA and OUTB connections is the probes of my multimeter.

I have only used a 24V DC adapter to test the board and connected that output to the GND and VIN pins.

I did not solder any header pin into the 3v3 or VM precisely to avoid accidentally shorting them.

If I connect my 24v wall wart (multimeter confirms it is 24v) the board gets hot as I mentioned and there is no voltage between GND and the 3v3 via.

Also I removed the large capacitor in a last ditch testing effort. No difference with capacitor there or not.

Thank you for the pictures and extra information. I am not sure what might have happened to the board, but the behavior you are describing does make it sound like it is damaged. If you send us an email at support@pololu.com with your order information and a reference to this forum post, we can see how we can help you out.