I found the-low-output-voltage-ripple-zeta-dc-dc-converter-topology and tried it out in LTSpice. However, the second channel doesn't behave correctly. Even when both channels are using the exact same circuit, only the second exhibits sub-harmonic oscillation.
The attached screenshot shows the LT8471 schematic with two identical inverting Cuk circuits, and the steady-state collector voltage waveforms. V(C1) looks correct, with a 1MHz switching frequency and steady duty cycle. But V(C2) is alternating between short and long duty cycles.
My only explanation is that the slope compensation functionality was left out or broken in the second channel. I would appreciate any input.
[edited by: erwingESI at 10:55 PM (GMT -4) on 3 Oct 2018]