Please first go trough the list of possible failures in the application note document and report back.
Pasted from the list:
Q: What are possible causes for a driver IC failing / becoming too hot?
A: These are some hints for failure conditions, which can (but don’t need to) damage the driver ICs:
• Motor Voltage above 34V (for non-A-types) / above 40V (A-types) or logic supply voltage above 8V
• Pulling motor connector during operation
• Short to GND without high side sense resistor
• Soldering problems (unconnected or shorted pins)
• Motor current set to more than 3A for extended periods of time
• Missing or far too small oscillator capacitor
• High ESD voltages applied to circuit before soldering it to board. We have never seen this happening, but please remark, that the drivers are sensitive to electrostatic (dis)charge, especially before soldering the IC onto the application board.
• Missing GND connection when powering the unit with a laboratory supply
• Missing Rslp resistor (or too high value)
• Missing short to GND resistor (or too high value)
All of these are severe violations of the drivers specifications. In fact the devices are very rugged and may be operated well beyond spec without problem.
For users having only very occasionally occuring problems, please see here: http://www.trinamic.com/ttdg/viewtopic.php?p=2485