Hello Kotaro-san
Two or more UCC28950 devices may be paralleled as shown below.
The master device operates in peak current mode. Its error amplifier output at the COMP pin sets the current demand level for the current loop. This current demand level is passed to the slave devices. The error amplifier of the slave devices is set as a voltage follower and the COMP pin of each of these slaves sets the current demand level for each slave. This should give equal current sharing across each of the power supplies in the system. There are of course some error terms to be considered - the input offset voltages of the slaves will affect the sharing but this should be relatively small. Vios is ±7mV and the CS signal range is to 2V. Differences in the current transformer signals from each of the power trains will also affect the current sharing, but again this would be a relatively small effect. Current sharing will be best at high load currents and poorest at light loads, in common with most current sharing systems. NOTE: The devices marked 'slave' in the diagram should be configured as slave devices (Rt connected to GND - page 23 of the datasheet) and they may be synchronised in the normal manner if this is desired.
The other alternative is to use a load voltage droop method to force current sharing. This is inherently less accurate than an active method but has the two advantages of simplicity and not having a master/slave arrangement.
I don't have a more complete schematic than the one below.
Please let me know if you have any questions.
Regards
Colin
