Best switch mode design to step down 5-12v to 5v at 1A?

Hi,

I'm trying to design a switch mode step down buck regulator on my ATmega-based microcontroller board that will take 5-12+v from a LiPo or other power source and convert it to 5v with max current 1A.

I'm new to the field of power supplies/regulators, so I don't yet know exactly what would work well and what wouldn't.

I've looked at TI's TL2575 ICs, which are 1A "simple step-down switching regulators." Only four external components are needed (inductor, 2 caps, schottky diode), and it's 85+% efficient. The problem, however, is that it requires a big 330uH inductor that is expensive.

I then moved on to looking at another TI chip, the TPS63061 (kind of hard to find...just released in Dec. 2011). It is a buck-boost converter with 2A max current. This will allow for an input lower than 5v, as well as above it, so it would work great with 1/2-cell LiPo batteries. It uses a 1.5uH inductor, some small caps, a resistor, and a pretty big 66uF ceramic. Overall, the footprint is much smaller, but the total cost is a bit higher. Here's a basic schematic.

I've also been on WEBENCH and desiged a 6-18v input, 5v/1.6A output regulator with the TI LM20333.

What design would you suggest?

Thanks for the help!

Michael

0 Catwell over 13 years ago

Michael,

Making a switching power supply like the TI LM20333 is an elegant solution.

Could you get away with using a LM7805LM7805 or LM78XX series linear regulator? It would be the simplest, one component, option. The LM7805ACT.LM7805ACT. linked here can handle up to 20V input.

Cabe
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0 RWM over 13 years ago

It depends on what you need. LM20333 is buck converter, so you cannot have input voltage lower than 6V perhaps alittle bit lower). There are available less buck-boost converters than buck only. TPS63061 is interesting, however do you have experience soldering tiny SON packages? If you plan to use 1 LiPo, you need boost converter. If 2 LiPo - buck. If 1 or 2 LiPo - buck-boost (SEPIC).

You can look at Linear:
http://parametric.linear.com/switching_regulator#!1038_yes!1646_Buck-Boost|SEPIC!1032_%3C=3!1033_%3E=12!1105_%3C=5!1034_%3E=5!1035_4:24!1107_1:6!vinmin_3!vinmax_12!mono_mono!vout_5!iout_1
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0 Former Member over 13 years ago in reply to Catwell

I initially thought about using a simple linear regulator, but with the amount of current I would be using I'd probably have to put a heatsink on the board. I think it would be better to use a switch mode regulator to aim for most efficiency and low power dissipation (albeit a more complex design!)
The LM20333 looks like a good solution, but I'm thinking maybe the TPS63061 would be even better because of its buck-boost SEPIC design and smaller inductor? I've never soldered SON/QFN packages before, but I just ordered a few Schmartboard breakout boards to help with the initial prototype.
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0 RWM over 13 years ago in reply to Former Member

For input 12V and 1A load current heatsink would be big (7Watts) so it is better to use switching converter. I think you can try TPS63061 or check LM5000/5001 http://www.ti.com/product/lm5001
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