Connecting multiple step down converters together in parallel

[woody363]

Hello,

I'm trying to connect two SDC boards in parallel so that they can handle more current. I'm fairly sure one acts as a master and there can be multiple slaves through use of the sync pins. The datasheet is available here: http://www.farnell.com/datasheets/1746752.pdf

There is also this datasheet: http://www.farnell.com/datasheets/73783.pdf which as far as I can tell is for the same device but with the descriptions of JP1 and JP2 reversed (which is rather worrying).

I also don't understand how to reconcile the two sync outputs +'ve and -'ve but only one sync input.

I have cut JP1 on one device (slave) as indicated by the first datasheet and connected the positive sync out from the master to the sync in for the slave, as this seemed the most sensible interpretation.


The two devices are connected at common, Vin and Vout. I expected the slaves voltage to sync up to that of the masters, however the output voltage simply reads as the highest of the two. Current doesn't seem to be evenly distributed either. I'm therefore assuming that the sync hasn't happened.


two options:
1: There is a typing error in the first datasheet and I've cut the wrong jumper
2: The sync pins are connected wrong, quite likely as this was just a guess.

Anyone got experience with these boards?

Cheers,
Woody

[Richard Crowley]

The data sheet says that the current limit must be adjusted down to 20A if multiple units are used in parallel.