Replacement for U1 AP1117-3.3 on Nixieclock Rev6

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3 years 8 months ago #9362 by Joker
Hello,
for me, it's difficult to get a AP1117-3.3. Conrad sells LD1117AS33TR SOT-223. I think there is no problem to use these chip.

Input max. 15 V
Output min. 3.3 V
Output current 1 A
packaging SOT-223

What do you think? Is it neccesary to change C10 from 100µF to 10µF?

Thanks for your help
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3 years 8 months ago #9363 by Ty_Eeberfest
That regulator looks to me like it will work okay.

On the Rev.6 schematic I am looking at C10 is 100nF not 100µF. If it was me, I think I would just leave out C10. I don't know anything about the LD1117AS33TR specifically, but I have had trouble with other LDO regulators going crazy (very unstable regulation) when a 100nF or 220nF capacitor is put directly on their output, while others work just fine. I see that the LD1117AS33TR data sheet does not show any small (100nF or whatever) caps in any of the application circuits, so I would leave it out. The 10µF cap (C11) should be an adequate filter cap by itself.

Look into it later when the dust is clearing off the crater.
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3 years 8 months ago #9369 by Ian
Look for an AMS1117, they are the same in every other way, except they don't go crazy se easily. I'm moving totally away from AP1117 and to AMS1117.
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3 years 8 months ago #9376 by Joker
Thanks for your respose.

I ordered some AP1117 on Ebay.

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3 years 7 months ago #9379 by Ian
If you go for the AP1117, be aware that the data sheet says that the capacitor needs to be a tantalum one (for stability, apparently). I'm not sure how much this really matters, but they don't usually write things like that for fun, but of course ringing will depend on the load and countless other factors.

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