This is something that is troubling me in many of my projects and I would like to know if there is any standard approach to it.
The question is how should I correctly design / dimension my power supplies to be sure that enough current will be available for my CPU.
I am using various packet processors from Marvell and at every one of them they provide, like CPUs from other vendors, two different set of current/power specification.
One set is the TPD (thermal power dissipation), where they say that this numbers should be used for the thermal design. The numbers are measured under nominal voltage and some selected use case.
The second set is the maximum continuous current that can be drawn from the power supply and is given to support the power supply design and selection of power module. These numbers are given using maximum recommended voltage specification for the power rails, at max recommended operation temperature and some extreme use cases.
One could say that the answer to my question is obvious: use the second set of data for correctly selecting the power supply, since this is why they are given for.
But the thing is, these numbers are at maximum recommended voltage (usually +5% of the nominal voltage) and at maximum operation temperature. Both of these conditions are not met at my designs.
Is there any standard approach to this? Should I just use this maximum continuous current specifications when defining the maximum current of my power supplies or should I somehow (how?) at least scale them down to the typical voltage supply?
My concern is not to over-design the power supply, since the numbers between the two sets differ -usually- a lot.