How to connect multiple LT8491 in parallel?

The two LT8491s could be synchronized using the CLOCKOUT but would need to function independently. It is better to use the LT8705A if additional current is needed. See DC2285A. This demoboard has two LT8705As in parallel with the option of connecting the LT8490 as the master. This could easily be adapted to work with the LT8491 instead of the LT8490.

If I am designing a master-slave load sharing circuit and have a master LT8491 and two LT8705A slaves, and I need a total of 21A, what should I size my sense resistors to?  Should the master and two slaves each sense 7A, or does the master need to be sized to sense the full 21A? 

How are the resistors and capacitor on the VC pin calculated?  And should the master LT8491 and three LT8705A slaves have the same loop compensation?  My input is 10 to 70V and output is 34V at 5A each (20A total for one master and three slaves).  

Thanks 

Given the same input and output levels, the LT8491 and LT8705A should have the same compensation values. You can determine compensation by using LTPowercad and using the expected current for one phase only.

If I have one master LT8491 and 3 slave LT8705A's, do I need input current sense resistors on all the slaves?  I'm looking at DC2285A and the slave LT8705A doesn't have an input sense resistor.  Why are CSNIN and CSPIN tied together?  Thanks again.

You do not need to have an input current limit. If you desire one then set up appropriately. If you don't want an input current limit then tie the CSPIN and CSNIN together and connect to the input as shown.

Can I tie all of the CSPIN and CSNIN pins together for the master and three slaves as shown in the schematic above if I don't need an input current limit at all?  

CSPIN/SCNIN is used in the MPPT algorithm so if you need that function then you need to keep in the input current measurement.

Can you please explain the logic behind connecting IOW and LDO33 from the master LT8491 to the Optional LT8490 Interface circuit work?  How does it work?  Thanks again.

If you are referring to the DC2285A markup I provided earlier, all references to the LT8490 should be replaced with LT8491. J10 pin 2 connects to LDO33 of the LT8491.

Right, I'm trying to understand how it works.  It looks like IOW from the LT8491 is modulating its own IMON_OUT before it is fed into the buffer U4A.  How is this changing the output current limit and load sharing?

IOW changes the output current limit. This is a function described in the LT8491 datasheet. See your local ADI FAE to get a more in-depth explanation of Master-slave control of the LT8705.

IOW changes the output current limit. This is a function described in the LT8491 datasheet. See your local ADI FAE to get a more in-depth explanation of Master-slave control of the LT8705.