I am using the LT3845A to design a step down converter from 32V to 5V with around 6.2A output. During the testing phase, I can go up to 3A with no problem. But as soon as I get to around 4A output, I start noticing some harmonic oscillation on the inductor current waveform. It gets worse at higher load until at 5A where I can't maintain my 5V output anymore. The problem also happens sooner as the duty cycle increases (lower input voltage). As far as I know, harmonic oscillation should only happen at above 50% DC so I don't exactly know what is going on here. Any help is appreciated.
3A output. Channel 1 is the top gate voltage. Channel 2 is the bot gate voltage. Channel 3 is the SW node voltage. Channel 4 is the output inductor current
4A output. The current inductor waveform starts oscillating
Oscillation getting worse at 4.5A output