I have an application in which I'm using multiple LTC7138s to provide more current than available with a single device. As I understand the operation, the primary device will cycle the FB pin of the secondary device(s) to produce burst cycles from the secondary devices. My questions are about the arrangement of the programming pins on the secondary devices. The datasheet shows two examples (pasted below) which each have different programming pin arrangements. As I understand the operation, the primary device really just needs to drop the FB pin to a low enough value to trip the internal comparator to trigger the burst mode on the secondary devices, and it needs to do this with an appropriate frequency to properly regulate the load, so I can see how either of the programming pin arrangements would be valid. I believe the different arrangements would ultimately just affect the timing of the signal from the FBO pin of the primary device.
My questions:
- Is my assumption correct that either programming pin arrangement is valid based on my stated understanding of the operation?
- Are there pros/cons to different programming pin arrangements, and specifically, is there any benefit to matching these between the primary and secondary devices?
Datasheet example 1:
Datasheet example 2:
