I'm planning on using an LM1117 to regulate 5v to 3.3v. Looking at (any of the several) data sheets for the LM1117, they recommend 10uF Tantalum capacitors between input and ground and between output and ground. I understand the need for the capacitors, but it's not clear to me why these should specifically be Tantalum. I have a bunch of electrolytic 10uF capacitors sitting around here, whereas if it does for some reason need to be Tantalum, I'll have to order those.
Why are they so specific about using tantalum capacitors?
The LM1117 datasheet provides clear guidance on the essential and desirable characteristics of the input and output capacitors. Any capacitor which meets these specifications is suitable. Tantalum is an OK choice but is not the best choice. There are various factors and cost is one. Tantalum offers OK cost per capability at capacitances from about 10 uF up. The output capacitor is "safe" against spikes in most cases. The input capacitor is at risk from "bad behavior" from other parts of the system. Spikes above rated value will produce a (literally) flaming melt down. (Smoke, flame, noise, bad smell and explosion all optional -
I have seen one tantalum cap do all of these in turn :-))
I think you have the wrong pinout for the LM1117.
ReplyDeleteUnlike 'normal' 5C regs, e.g. LM7805CV, The LM1117 has the V(out) in the centre, or so I believe.