The expansion connector on a SPLat board carries two power supplies: The raw power input provided to the board and the board's internally generated 5V supply. On some boards we may make any other voltages available.
The 5V supply on a board is designed mainly to supply the needs of the board itself, be it 50mA or 250mA. There will usually be only a small amount of spare capacity. The raw power can vary from board to board, on some boards 10-24VDC, on others 9VAC, 18VAC or 24VAC.
This leads to restrictions on the power supplied to an expansion board.
SPice and SPiceX boards, especially ones that plug piggy back directly onto the host SPLat board, must by definition make do with whatever power they get from the host. This could place constraints on allowable supply voltage supplied to the SPLat board when used with a given SPice board.
SPx boards will more often than not require a power supply that meets the SPx board's specification.
This all means that when deciding on a power supply you must consider both the needs of the SPLat board and of the expansion board(s). Please consult the product documentation or ask us.