A4988 failure why?

I am using 3 A4988 to control 3 stepper motor in a home made cnc but I have distroyed 3 of them in the first board, I used the minimal wiring and it worked during a while but one of them blowed up literaly.and the other 2 cuntinued working but both at a time gave up.
I modified the circuit with the control lines opto coupled and I added capacitors to each one 4,7 microF and 100 nF the board works properly during a while but sudenly one of the the A4988 blowed up again.
The parameters are a 12v rated motor 33 ohms coil and 330 mA current and in my board I,m using a pc power suply with a fullbridge diode to avoid wrong conections so the avaible VDD is 10,9 quite lower than required and before using it I adjust the I max in 240 mA and I dont know why the drivers blow up.
Thank you in advance.


Can you post some pictures of your setup that show how everything is connected? What was the board doing at the time of failure? Did you make any changes to your system around the time the boards failed?

- Ben

this is the schema for one chanel the others are equal but only one regulator is used

Althoght the ic is downside i placed a disipator

The circuit when the driver failed was not moving it had the coils energized but static

Did you make any changes to the circuit shortly before it died? Did you ever disconnect the stepper motor while the coils were energized?

I do not see any problems with your connections, but your heat sinks worry me. Is there any chance that your component-side heat sink is touching any of the components on the board? Also, could your bottom-side heat sink be creating any unintentional short-circuits? There are several untented vias on the underside that the heat sink could be touching.

- Ben

  • If this is the problem (posible heat sink short circuit) could I use the drivers whitout them? in a safe way?
  • the first 3 get distroyed whitout heat sink is it normal? or they should shutdown before ?
  • Are the heat sink realy necesary if current is fixed in 240 mA per coil.?
  • The only change I did whit coils activated was disconecting the suply, is it dangerous?
  • I added the enable switch because of this to disactivate the coils before switching power of.

I make all this questions to find a posible reason of mi problem.
Thank you very much for your interest

You shouldn’t need a heat sink for that low of a current limit, and the driver has built-in thermal protection, so using it without a heat sink in general should not damage it (it just might not work well without a heat sink in applications that require more than 1 A per coil). Cutting power while the coils are energized should not damage anything, nor should using the board without a heat sink. I’m not sure what is causing the damage in your system, but maybe something isn’t outputting the voltage you think it is, or maybe your grounds are not connected properly?

- Ben

thank you very much for your answers I will check wiring again for shorcircuit or incorrect grounds and try it again.