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I would like to know if its possible to 'step up' the voltage from two AA batteries (3V for Alkaline and 2.4V for NiMH) to a stable 3.3V ?

I need to find a good power source for a circuit that I'm building which controls a few LEDs with an attiny45 chip running at 3.3V.

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  • \$\begingroup\$ Why not switch to a device that works all the way down to 1.8V? \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Jul 29, 2015 at 13:51
  • \$\begingroup\$ @IgnacioVazquez-Abrams Cause LEDs won't? (I use RGB LEDs). \$\endgroup\$
    – YemSalat
    Commented Jul 29, 2015 at 14:27
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    \$\begingroup\$ An inductive driver (by which I mean an inductor driven with PWM) could probably light them. Although to be fair, I haven't tried it myself yet. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Commented Jul 29, 2015 at 15:39

2 Answers 2

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Sure, there are plenty of step-up chips available. Your case is easier than some because you don't need to worry about the input voltage exceeding the output voltage (3.2 is probably the highest voltage you can expect from two AA cells).

A reasonable minimum voltage is 1.6V for two cells. You could use the Skyworks chip as shown below- one of the cheapest and smallest solutions, but there are other modern chips that are similarly minimalist in their requirements and cost. Be sure to use the recommended layout, component types and one of the recommended inductor part numbers unless you really understand what is going on.

enter image description here

To prevent damage to the rechargable cells you may wish to have the circuit shut down at some minimum voltage. Many modern boost regulators will happily operate until they've completely flattened the cells (the above one will typically continue to operate to 250mV/cell).

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    \$\begingroup\$ Hey thanks Spehro... I didn't know about that particular chip, so I'm glad I happened by. \$\endgroup\$
    – Randy
    Commented Jul 29, 2015 at 14:24
  • \$\begingroup\$ Thanks so much! This really helps, just one more thing - is there any particular component 'general name' that I can google for? (I mean specifically for this low-voltage kind of step up converters) Unfortunately I can't come up with any proper search terms. \$\endgroup\$
    – YemSalat
    Commented Jul 29, 2015 at 14:34
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    \$\begingroup\$ Try Digikey's parametric search engine. Product Index > Integrated Circuits (ICs) > PMIC - Voltage Regulators - DC DC Switching Regulators, then select 'in stock', 'step up' function, minimum maximum voltages, fixed or adjustable output, output voltage etc. Using reasonable guesses I get about 30-40 results when pared down, some of which will be duplicates with different temperature ranges etc. so not too many to go through the data sheets (more than 10,000 SKUs before paring down). Many more types than the 30-40 if you are willing to add a couple resistors to select the output voltage. \$\endgroup\$
    – Spehro 'speff' Pefhany
    Commented Jul 29, 2015 at 14:44
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You can use a "low voltage boost converter", "ultra-low voltage boost converter" or "low power step-up DC/DC converter".

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