SMPS buck convertors: high frequency or low frequency?

[nedflanders]

high frequency smps

Hi everyone,

I'm designing a switch-mode power supply for a small robot and I'm wondering if anyone has experience with high-frequency (~1MHz) buck convertor design.

Here are my basic requirements for the supply:
-Nominal supply current: 100mA
-Max supply current: 1A
-Max Vin: 15V
-Vout: 3.3V

Goals in order of priority:
-Small as possible
-Not too much EMI
-Efficient as possible (ie synchronous)
-Internal switch
-Cost isn't really an issue since this is for low volume

To tick off small and efficient I'd like to use something like the TPS62110 from TI, but I'm concerned about EMI. This will be powering analogue sensors (gyros and accelerometers), and I want to make sure my measurements aren't too noisy. From what I can tell, proper layout (fat tracks from switch to inductor, minimal loops in the supply) should prevent EMI in the first place. Anyone have experience with high frequency switchers?

Cheers

 

[VVV]

efficiency of high frequency buck smps

Since the switches are integrated, there is not much to be considered about the design, except the layout. Layout is key to good power supplies.
Once you have a layout in mind, you can send it to me and I can take a look at it and provide you some feedback.

Also, if you are really concerned about EMI, in your case I suggest you use a shielded inductor. Avoid the "open-core" or rod inductors, as their magnetic field will induce voltages in every trace nearby.

You should also consider the output ripple. Try to minimize it by using low ESR caps (ceramics). You may also consider using filters on the supply rail for your sensitive sensors. Small LC filters (ceramic cap plus a small inductor or even ferrite bead) can do a good job. But I would determine first if the noise really affects them. If the switching frequncy is high enough, it is possible your sensors will just filter it out themselves.

Regards,
VVV