Double check that the enable line is being held low until you want motors enabled. The main thing if I recall correctly is to have 5V up and stable before supplying Vmot, and then enable the drivers. If you let enable go high before 5V (and possibly Vmot) it can burn out the chip. The enable line is active high, which is opposite from Pololu drivers which have an active low enable line. Also make sure your current limiting resistors are sized appropriately. Other than that the only other thing I've run accross that will burn them out is a cross connected motor. If you short either coil A output to a coil B output it will fry.
For the cannonical power on sequence see the datasheet. But I think the enable line is the critical one. Make sure you don't enable till the chip is powered up and ready.
Other things to check would be cold solder joints. A floating ground pin or some other pin might cause something like that.
Bryan
For the cannonical power on sequence see the datasheet. But I think the enable line is the critical one. Make sure you don't enable till the chip is powered up and ready.
Other things to check would be cold solder joints. A floating ground pin or some other pin might cause something like that.
Bryan