LTC3769 boost converter becoming damaged

Hi JKK,

Have you verified your design using LTpowerCAD then LTspice? I would suggest to double check the layout checklist found on pages 24-26 and the layout debugging guidelines on page 26. You could also check your board for manufacturability issues such as wrong component values or poor solder.

Hi JKK,

Have you verified your design using LTpowerCAD then LTspice? I would suggest to double check the layout checklist found on pages 24-26 and the layout debugging guidelines on page 26. You could also check your board for manufacturability issues such as wrong component values or poor solder.

Hello and thank you for your reply. I have checked the pcb layout against the recommendations in DS. I find a few potential areas of difference, one is that the output bulk electrolytic is placed quite a way from the output  (about 3 inches), output ceramics are close though. This impacts recommendation 2. Recommendation 7 seems tricky to implement. Our design has the Vfb, Freq and Ith resistors tied together  in an AGND puddle on an internal plane and single point connected to EP via pin 4.  
As far as simulation is concerned, LTspice doesn't show any issues like overshoot or overvoltage. LTPowerCad did indicate a red PM parameter for 5V input operation. 
I don't believe our issue has anything to do with wrong components as we replaced the faulty chip with a good one and it worked successfully without changing anything else. I guess it's possible that a pin or the EP was not soldered adequately but it did seem to me that the chip itself has gone faulty. 
I could make the PCB changes in line with the above but would be somewhat reluctant to make a change without having good evidence that it would fix the problem. 

If you are reluctant about the PCB changes. You could try getting hold of the demo board DC2173A and make the necessary changes from there. It is good to have a working reference board when debugging.