I'm in the third year of my electrical engineering major and I want to take things a bit further than the usual analogue electronic circuits I've studied thus far by making a DC-DC step down converter that would convert 12V dc to 5V DC and output 3 amps of current.
So far I've only designed a PCB and I've gathered my components, but before I actually start assembling everything, I would like some advice from you guys especially since I can't test the components since it is my understanding that using a breadboard is not a good idea and perf boards are not really easy to get for me.
The schematic and the design of the PCB are as follows:
You can tell from the schematic what components I will be using, however I wasn't able to find those exact resistors. The closest I could get was a 1k resistor and a 3.3k resistor for the voltage divider resulting in 1.163 volts instead of 1.21 or thereabouts. Alternatively, I was able to find 4.7k and 1.5 k resistors which would give me 1.21 volts, however the error for all these components are 5%. Every electronics store I've been to, I was told 1% resistors are considered military grade so they don't sell them or some other bogus. I bought 20 pieces of each of the four resistors and I'll try to pick the ones with the closest value to the theoretical one (using a multi meter) but I don't know how they would fare with changes in temperature and load and what not. So this is one aspect I need help with.
I also wasn't able to find a 22uH inductor that could take 6 amps (apparently it is recommended that I should choose an inductor that could take twice the current the converter will supply) however I was able to find 11uH inductors rated for 6 amps and I was wondering if it would be ok to connect them in series.
And I forgot to mention this the first time I posted the question but I also was not able to get the diode that is in the schematics but I was able to get an SB560 diode which as far as I can tell from the data sheets, it should do the job but in any case if any one would like comment on that, it would be great.
What are your thought on this?