The industry of Electronics is going through a paradigm shift as there is an increase in demand of devices which consume less power. It also had a significant effect on hobbyists, tinkerers and engineers as market for 3.3v components and devices started sprouting up. Even though it seems like many choices exists to make our 3.3v power supply in paper but practically its pretty limited.
The problem when coming to building a 3.3v power supply is that selection of regulator IC can be limited and confusing. And trying in internet didn’t give me many choices. So this article will serve as a guide for you to build your own 3.3v supply.
Am pretty sure your search for 3.3v regulator will lead to this IC. And it seems pretty obvious to use this IC as your 3.3v regulator with additional few caps in your circuit. A nice steady 3.3v supply will be ready. But there are a lot of various versions in this IC that you need to be aware of. If you prefer buying IC’s from online vendors you don’t have much to worry about but if you prefer local stores and vendors you may need to look out.
LD1117 comes in different versions which is capable of supply output voltages in the following ranges. 1.2v, 1.8v, 2.5v, 2.85, 3.3v and 5v. And above all this IC also comes in adjustable version which is capable of providing different voltage ranges. Also this IC costs around $1 each and you wouldn’t want to buy a wrong one for your application.
Here is the list of available LD1117 voltage regulators. You need to cross check with this sheet to see if you are buying the right one, I mean the regulator which gives 3.3v output. Now you know which IC based on your preferred package to buy for your application.
This is a typical circuit that shows how to use the LD1117 series IC’s for deriving fixed output voltage ranges. Make sure you use the cap values shown in the above circuit or you might face deviation in the output.
3.3V POWER SUPPLY CIRCUIT USING ADJUSTABLE VERSION OF LD1117:
In case if you have got the adjustable version of the IC by mistake, not to worry. You still can obtain 3.3v from the above circuit. All you have to do build a voltage divider between the Adj and Out pin of this IC. The formula for calculating the R1 and R2 values is
Vout = VRef( 1 + R2 / R1 )
Datasheet states that 1.25 is reference voltage. Fixing the R1 as 120 ohm for 3.3v output gives R2 value as
3.3v = 1.25( 1 + R2 / 120 )
R2 = 196 ohms
Fixing the R2 value as nearest resistor element 200 ohms, This will give 3.3v as output from the above circuit. The cap 10uF tied to the voltage divider is meant to remove ripples from the output for a constant voltage level.
Hope you find this guide useful to build your own 3.3v power supply circuit. Your thoughts and feedback are welcome. If you know any other circuit or way for this purpose do share it in the comment box, i will be happy to add that in this article. Happy DIY .
Source: gadgetronicx.com – Electronics