Need advice on component selection
Hi folks,
I'm looking for a step-up DC-DC voltage converter.
I need an output of 3.3V with a peak current of 500mA. Typically current will be ~100mA but can reach 500mA for several seconds at a time.
The input voltage will be approximately 3 volts (2 AA batteries).
I've searched far and wide and the only regulators I can find that can step-up to 3.3Volts don't meet my current requirements.
Any suggestions r/askelectronics?
Thanks, Adam
Posted Jul 8, 2015, 3:25 AM UTC
413
why not one of these?
http://www.digikey.com/product-search/en?pv7=3&pv7=2&pv7=6&pv129=2169&pv129=164&pv129=2087&pv129=2055&pv129=2058&pv129=2063&pv129=2067&pv129=7&pv129=2112&pv129=2118&FV=fff40027%2Cfff8029a%2C1b803b5%2C1bcc0032&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25
the thing you ought to remember about step-up regulators is that they're basically rated for input current, (switch current) not output current.
That list is perfect.
Thanks a ton. Not sure how I didn't consider searching Digikey. I was doing google searches for things like "step up dc-dc 3.3v 500mA" and I was getting nothing.
Thanks again.
Wait a second. I actually am not sure I understand your final comment.
The regulators you've sent me all have input voltages in the range of 0.8 to 3.3 V and all output at 3.3V. That part is great.
The property I am looking for is a supported current output of 500mA. These devices typically support smaller currents with smaller input voltages and larger currents with larger input voltages. Am I missing something because I don't understand your comment about these devices being rated for their input current.
Thanks adam
those two statements are basically equivalent.
Ah, ok.
In that case I'm back to square 1. None of the devices support an output current sufficiently high with an input voltage of only 1.5V.
I should've said before that the two AA batteries are in parallel and not in series.
Even if we put them in series, which is do-able, we would run into the problem that when they are fully charged they would potentially exceed the output voltage of 3.3 volts and then our step up regulator would fail because it requires that V_i > V_o.
Best, Adam
read the datasheets. i think a lot of those just turn into linear regulators when that happens. as long as the batteries don't exceed 3.3v by a lot, losses will be minimal.
Actually, no it wouldn't. It would just pass through the input unregulated, which is unlikely to be a disaster. (The voltage drop depends on whether they use synchronous or Schottky diode rectification.)
Plus, what AA batteries do you have that will produce more than 1.65V each? Even very fresh alkaline (non-rechargeable) batteries barely reach that, and rechargeable chemistries (NiCd and NiMH) operate at lower voltages.
In your post you said you wanted a regulator to go from 3.0V to 3.3V at up to 500mA.
Now you're saying you want to go from 1.5V to 3.3V at up to 500mA.
Good luck sourcing over 1A from a dying AA battery. What you're trying to do is not feasible unless you start using supercapacitors on the output stage - the battery can only provide so much energy.