I'm close to finishing my first 4-layer board. Initially, we felt that keeping the power supply as a separate unit would be better. This was because we wanted to avoid having heat on the main PCB - mostly because the area where the device is intended to be used is very hot and also quite dusty (heat from regulators would require ventilation, which would let a lot of dust in). However, I was also told that by keeping the supply external we would need to have massive expensive capacitors on the main board to filter out noise. So, as such, I'm debating weather I should keep my power regulators external or on the main PCB. I intend to go with linear regulators and require three rails - 1.8V, 3.3V and 5V. The majority of the current draw is on the 3.3 rail -- max 1A. The 5V is connected to a graphic LCD which draws a max. of 350mA. The 1.8V goes to the core of two CPLDs and I'm not yet sure how much this draws. Early power estimates suggest this is going to be less than 100mA. I should add, the board is designed to be extendable. As in, additional daughter cards can be connected to it to extend it's functionality. However, these would not have a lot of current draw. But if I do go with regulators on the main PCB, I will obviously need to them on the daughter boards as well. What would you folks think is a better solution? Is it possible that I can stick with linear regulators and use a package like D2Pak which allows good power dissipation and get away with not providing significant ventilation.