I am using LTC3769 controller for my synchronous SEPIC project. I have done full calculation and simulation for this configuration. And it works for simulation. However, when I am doing bench testing, Vds of synchronous MOSFET voltage rise quiet slowly which might cause shoot through problem. I have tried to parallel a Schottky diode with my MOSFET to exclude the reverse recovery effect of the MOSFET body diode. But the problem still remains. The detail schematic and waveform are attached below.
Overall Pulse CH.1 Syn FET Vg - GND; CH.2 Syn FET Vs - GND; CH.3 Main FET Vds; CH.4 Syn FET Vd - GND
Main FET turn-off
Main FET turn-on
As you can see from last waveform, the main FET seems turning on before syn FET turned off. Large negative voltage overshoot found on Main FET Vds. Do you have any suggestion for this problem?