I used LTC3766 and LTC3765 to build an isolation power supply, the input is 18V, the output is 15V, 15V has no load. The circuit is very similar with the evaluation board of DC1739B-C and the circuits given on the data sheet of LTC3766, but the output is not right. The 15V output waveform is shown below:
1) Yellow is the 15V output
2). Yellow is the 15V output. Blue is the PT+ of LTC3766.
It seems that the LTC3766 start to work for a short time, then due to some reasons, stop working. The IS+ and IS- of LTC 3766 is shorted on PCB board.
What could be the reason for this?
Your help is very appreciated!