Hints on switching power regulators

Forum 2005-2010 (read only) Hardware Development
1

I want to switch my current project to battery powered. I already optimized power consumption using sleep. I will also decrease the crystal clock to 8 MHz in order to decrease the voltage to 3.3V (which is what my display wants to have).

I plan to use two AA cells to power my toy. It will consume between 10uA (display off, Arduino in deep sleep) and 100mA (display on, backlight on, Arduino running, Arduino driving some opto couplers).

Are there any recommendations for a suitable switching power regulator? Design constraints would be:

  1. Reasonable simple to design a board around it
  2. Low current consuption with loads <10uA, should not consume >10uA on its own for such load conditions.
  3. Ready available, especially in low quantities
  4. Cheap
  5. Reverse polarity protection would be nice but is not a must have
  6. Short circuit protection would be nice but is also not a must have

I have not very much knowledge of PCB design but I intend to use Eagle.

Has anyone any hints for me?

Udo

2

TI makes a nice DC DC converter:

http://www.ti.com/corp/docs/landing/tps63000/index.htm

They've got standard circuit examples. What's nice about this guy is that you could, if you wanted to push it, use a single AA cell.

3

If it were me (and I'm seriously cheap) I'd just hook the 2 AA cells to the vcc and gnd lines direct. Providing they were alkalines, it would live on the 3-3.2 volts they put out. Ticks the first 4 boxes......

4

National and Linear Tech have on line simulators - easy to use

5

@pluggy the problem is that this won't work well with NiMH cells

6

I got fed up with Nimh cells, they have this delightful habit of self discharging over a period of a month or 6 weeks. I have a digital camera I use at infrequent intervals, when I wanted it the batteries were always flat and the backup set I kept outside the camera, were flat as well. I use alkalines in it now because when I want to take a couple of pictures it works without having to charge the b*ggers first...

7

Pluggy: I will go for NiMh. Even with Alkalines I want a switching regulator. I did not spend several weeks to optimize power consumption in order to not squeeze the maximum possible out of the cells.

With regard to NiMhs, I always go for Sanyos, they are much better than most others and I do not mind to charge them prior to use. If you use the Eneloops even this is not really an issue anymore.

The TI converter is a bit overpowered for my needs --> I will have a look at LT and National.

Udo

8

I got fed up with Nimh cells, they have this delightful habit of self discharging

There is new technology ("low self discharge" or "pre-charged") that minimizes this, typified by Sanyo "eneloop" series. They seem to work quite well!