I'm working on a twin power source (2 x 17V @ 5A) using the LM2642 chip. Each channel works perfectly when the other is disabled, although I did find a considerable difference in compensation requirements between the two. When I have both channels running I get an alternating duty ratio on both channels which, again, differs between the two.
Initially I suspected a spike on the current ramp, or perhaps the Vdd rail, as being the culprit but so far none of the usual fixes have worked. Has anyone else encountered this and found a cure?