Sorry, I suppose I was vague.
Here's the deal:
-FPGA needs 1.2V and 3.3V
-PLL needs 1.8V and 3.3V
-input voltage max of at least 9V with current of 2A for each source
-the regulators need soft startup, tracking during ramp-up, and pre-bias startup capability, and synchroznized clocks
THis last part has a couple of catch 22s:
- since I want the regulators to be running off of one of the clock outputs on the PLL, but at the same time the regulators need to power the PLL. I had reasoned that I could get around this catch 22 by powering the PLL off of a linear regulator directly since it draws so little current on it's own.
-and heatsinkinks and the like won't really work because there is a board height requirement due to stacking the FPGA module (nothing specific, but mainly the heatsink can't be something that protrudes obviously above the other components on the board which kind of cuts out heatsinks in general).
@MNeary, those pre-bias, synchronization, and tracking capability rule out almost every buck IC out there. THe only ones I've found that have even 2/3 of those only have maximum input voltages of 5.5V. I've not actually found any that have have all 3. It's hard enough finding one with tracking and synchronization, but finding ones that can support pre-bias startup is even rarer.