I am not sure if we need datasheets to calculate power budget. The load requirement is given also with the number of loads.
The input and output power of the linear regulator can be found as
Pin = V X I = 2.5 X 1 = 2.5 Watt
Pout = V X I = 2 X 1 = 2.0 Watt
The voltage drop in the linear regulator will be 0.5 V which translate in to 0.5 Watt power dissipation.
There are six linear regulators. The input power to the linear regulators will be 6 X 2.5 Watt = 15 Watt.
Because there are two DC-DC converters so each will have to deliver 7.5 Watt. In other words the output of the DC-DC converter has to be 2.5 V and delivering 3 A current.
How about the input current to the DC-DC converter ? Given that the efficiency of the DC-DC converter is 0.8.
Does it mean that the input power of the DC-DC converter will be 7.5 Watt / 0.8 = 9.37 Watt for each DC-Dc converter. Is that correct ?
The input current to each DC-DC converter will be.
Input Current = Input Power / Input Voltage
Input Current = 9.37 Watt / 20 V
Input Current = 0.46 A
The total input current for both DC-DC converters will b than 0.46 x 2 = 0.92 A. Is that correct ?
The power budget to the power distribution board is = 20 V X 0.92 A = 18.4 Watt