I'm dealing with a power supply board based on LTM8068, input voltage 24V, output (Vout1) - 6V.
It works but I observe spikes at the output at the switching frequency (about 400kHz in my case) with the amplitude 200-300mV peak-peak, which seems excessive and this is a problem.
Could you please advise me for the probable reason and, if possible, remedy?
The scheme is quite basic.
Only Vout1 is used.
Cin is two 4.7uF, 50V X7R capacitors (datasheet recommends 2.2uF).
Cout1 is two 47uF, 10V X7R capacitors (datasheet recommends 22uF).
No Cout2 (as Vout2 is not used)
There is a 620 Ohm resistor for minimal load (within the recommended range).
Possible faults that I can find:
- pcb layout does not conform to the recommendations from the datasheet, in particular, Cin is close to the chip but it is connected to the ground through via and internal layer.
- the chips probably were not baked before mounting; however, I have several boards (from the same batch) and all of them behave similarly, therefore, random damage seems unlikely.
I need to find the cause of the problem; if possible, salvage the available items, if not - give recommendations to remedy it in the future iteration.
Any help would be greatly appreciated.
