Linear or Switching Power Supply for a Embedded Project

Question

Power Block Designing noob here.

I have a beaglebone 2x XbeePro(s) and another 500mAh device connected to the board i am building a PCB Around.

I need some advice on weather to use Linear Voltage Regulation vs Switching mode regulation.

Secondly if i am using linear voltage regulation setup do I need multiple regulators for the different devices?

My plan is to use A 2S 1000mAh Battery -> Fuse -> 2x 1.5A LM1084's in parallel output feed to the beaglebone and a LM3940 for both the XBees. Or its better to have each XBee on its on LM3940 drawing power from a seperate LM1084?

Linear Regulators tend to get hot on full load, hows the performance of Switching mode regulators ?

Answer 1

A linear regulator has a major drawback: it dissipates the power it doesn't deliver. Using the well-known 7805, the output voltage is 5V, your input shall be at least 7V to allow a good regulation (2V dropout voltage), if your load requires 1A, your 7805 dissipates 1A * 2V = 2W. This makes your Linear regulator hot. The best efficiency you may expect from a 7805 is 70% (and, to the best of my knowledge, a linear regulator doesn't exceed 80%).

Switching regulators are non linear. For a switching regulator, 80% is a poor efficiency (but sometimes acceptable for very cheap designs), power efficiency is usually around 90% under full charge, and may come up to 99% when large amounts of energy are involved, with an expensive design. For little loads, efficiency may drop to 60%, due to the power consumption of the regulator itself.

So, in my opinion, you should use switching regulator, for a better power efficiency and lower heat dissipation. If you need a single voltage, try to use only one regulator: it's cheaper, and avoid the little load situation. If you want to design a low power application, you'll probably have to choose a more sophisticated design, but it's probably not the case, as you use a beaglebone, which prevents you to manage each processor power supply independently.