I got a problem with LM5088 buck converter - namely the design is able to produce output at the designed 12V although it's output current is severely limited. My design assumptions were:
Vin - between 14 to 28 Volts (although wanted to gain some insight into regulation up to 50 Volts for other designs that are pending).
Vout - 12Volts
Iout - 8 Amps
I have used webench to get the basic design.
Here is my schematics and PCB layout (Connection between SW and Mosfet source has been wired on this PCB externally as apparently I forgot to add this connection in my schematics):
The problem that I've come across is that the converter produces some output that is not really what I would expect - it is clearly visible in the output that the frequency at the inductor is much different from the design point (524,55 kHz) (the smaller ripples that come just behind the 3 main ones are at almost the right frequency). The result is that the output current capacity is limited to around 1.5 Amps and beyond that point the voltage significantly drops.
Output voltage:
Output + Gate signal:
Here is output + feedback signal:
I have checked the design also in LM5088 Quick start tool and it seems that the compensation network parameters cause this setup to be already way shifted in the phase as for the design frequency. The question is whether all these oscillations in between the actual gate drive signal may be caused by compensation network being not tuned properly ? What would be the best point to look at more closely in finding the problem here ?
Best regards,
