SMD regulators

So I try to find some good smd regulators I've been using AMS1117 with the bellow diagram:

Any other suggestions about smd regulators 5v and 3.3v or I'm good with what I'm using?

Thanks,
D60

I find the 1117's work well.

what kind of capacitors do you use?

You can try this LT1083/LT1084/LT1085 devices are pin compatible with older 3-terminal regulators.

I normally default the ZLDO1117. The two are very similar, but the datasheet for the AMS1117 specifies a 22uf tant on the output, while the ZLDO1117 says that plain old 4.7uf ceramics will work. I use 4.7 or 10 uf ceramics on the ZLDO1117s, tants for 1117's whose datasheets don't mention using ceramics.

4.7uf ceramic caps sell for ~3-4 cents/ea in qty 100 (digikey)
22uf tants are ~15 cents/ea in qty 100.

Beyond their higher price, tants have a bad reputation, since in the event that they fail, their typical failure mode is to fail shorted and catch fire, so some people don't like using them. Ceramics, when they fail, it's usually because of a physical crack, and they just stop acting as capacitors.

If you need lower dropout, or some other spec that the 1117's don't have, I'd recommend looking through the digikey online catalog (whether or not you want to buy from them) - it lets you filter by all sorts of parameters.

thx billho

Interesting, arduino use on Uno AMD1117 with electrolitic capacitors but not tant, how's that?

Hm, the schematic says it's an NCP1117 - the datasheet for that goes into considerably more detail about the external caps, and says that electrolytics are okay provided they meet the criteria laid out there.

The effect of sub-optimal capacitors is usually just less stability than the regulators are spec'ed for. Some regulators deal with this less gracefully though - I've been told that some older models will oscillate when given a modern ceramic output cap.

None of the official Arduino boards are shining examples of good board design (not that they need to be) - they're not bad, but there are no shortage of questionable design decisions and places where they cheaped out.

This is an Arduino Uno R3 I'm not sure if it's original or not but it has everything on the board, drowings
even on the back full drawing of board name country, site..etc So probably it's original

This is from the board, my mobile camera couldn't focus closer.

As you can see it's an AMS1117 5.0 with 2x electrolitic caps 47uF 27v.

It's not an official board. Look at that green thing (PTC fuse), the corresponding part on the official boards isn't green. https://www.arduino.cc/en/Products/Counterfeit

Looking the link you gave the fake/copy looks better than original :smiley: lol
Well looks like its a copy, but even the original use electrolitic caps.

so what would happen if I use electrolitic caps on a AMS1117 or ceramic caps?
I use 10uF ceramic caps that's wrong?

They may have higher esr

Higher ESR?
So what do you suggest better to use for AMS1117, ceramic, tant or electrolitic?

I've been using LD1117 regulators for all of my projects, both 3V3 and 5V variants, with no complaints thus far. If I need a tighter voltage control then I'll deal with it, but I like having the 800mA of current capability for things like high-power XBees and such.

I use a 10uF tantalum on both input and output, and an additional 0.1uF ceramic on the output. Probably don't need to, but it's been working and I haven't felt like experimenting with it. Usually I see a similar setup on other boards, though the tants are sometimes replaced with electrolytics.

Clearly, the AMS1117 works with just an electrolytic on the output (as is done on many Uno clones), at least well enough for an Arduino Uno - but this is not consistent with the datasheet, and may not meet mfg specs for ripple, stability, etc under the full spec’ed operating range. So if you’re not using the caps the datasheet recommends, you need to assess whether it’s performance is acceptable under your operating conditions.

I make a point of only buying 1117 regulators for which the datasheets describe use of ceramic caps, since ceramics are so much cheaper, and so much more convenient, than tants, (electrolytics are a pain because they’re so bulky, and their higher ESR is often undesirable). I could probably get away with using different caps than the datasheet recommends, but I’d rather be confident that the regulators are working as they’re supposed to. No point in working outside mfg recommendations without a good reason.

So I should better use tants as the datasheet describes for the AMS1117?
Well I'm talking about 1117 because i ordered 200x of them 5 and 3.3 so I don't think i will buy any
other for long time :smiley:

I'm entering just right now in the SMD world, aren't those ceramic smd caps on that 1117?

I'm getting confused sometimes with recomended and what actually people use.

Btw what about the voltage of the tantalium capacitor? Should it be more than the input power supply voltage?

Domino60:
So I should better use tants as the datasheet describes for the AMS1117?
Well I'm talking about 1117 because i ordered 200x of them 5 and 3.3 so I don't think i will buy any
other for long time :smiley:

I'm entering just right now in the SMD world, aren't those ceramic smd caps on that 1117?

I'm getting confused sometimes with recomended and what actually people use.

Btw what about the voltage of the tantalium capacitor? Should it be more than the input power supply voltage?

You should set up your circuit as the datasheet recommends. If it says to use tants, use tants. Unless you feel like experimenting and testing stability with different types/sizes of caps, etc.

Tantalum voltage should be at least 2x (and more isn't a bad thing) what it will see. They don't like ANY overvoltage, and will usually blow instantly if over volted. So you don't want a tant rated for say 5V when you are feeding 5V in, as even a tiny fluctuation in that input voltage will result in possible fire. I generally use 16V tants - my input voltage normally comes from 5x NiMh batteries (~7.2V fully charged) or USB (~5V), so plenty of overhead there. The following video from Sparkfun shows you why you should do this: Bust a Cap - Exploding Capacitors with SparkFun - YouTube.

BillHo:
You can try this LT1083/LT1084/LT1085 devices are pin compatible with older 3-terminal regulators.

How do you dissipate the heat from such a small package with a 7.5 amp output and any reasonable input voltage?

I can see if it's soldered directly to a copper block, but no way simply soldered to a PC board (even with extra thick copper).

M package?

madmattd
Thanks for your explanation and nice video, I enjoyed it :smiley: Good to evil xD so tants are evil.

Well reading the AMS1117 Datasheet, I can use max 15v input so a xx.uF 20v tant. cap. will be good.

Looking this AMS1117 Datasheet:
http://www.advanced-monolithic.com/pdf/ds1117.pdf
You can see on Page 5, Figure 1 and reading “Stability” That’s the recomended circuit?
Strange…

ps(If tant. caps. are so bad I should better buy ceramic instead of tants, anyway you can see from my last picture in page nr.1 come china circuits are made with ceramic but the voltage is not accurate, I got one module and the voltage in not stable and higher than 3.3v)
Thanks,
Domino60

It's not the fact that it's a tantalum capacitor it's the ESR (equivalent series resistance) of the capacitor that matters. ESR is a measurement of how quickly the capacitor charges or discharges -- as if it had a resistor in series with it. Ceramic caps are about .01 ohms for a 22uF, ~2 ohms for a tantalum, and ~10ohms for electrolytic. Obviously the ceramic caps aren't a great choice but the electrolytic are a reasonably close match. But be aware that there's a lot of things that will blow these ESR values out the window -- the frequency/transience of the noise, notably.

Like you I bought my stock of AMS1117s, and personally I always use electrolytic (leaded, not SMD) caps and I've never ran into a problem. As a best practice, when I'm designing my own board, I add spaces for two caps on both the input and output -- that leaves you open to putting caps in parallel (which halves the ESR) or using a combination of larger (higher ESR) and smaller (lower ESR) caps so I can pretty easily cover any weird voltage fluctuations I hadn't accounted for. And the reason I use leaded caps is so I'm not stuck to the large SMD footprint and can get a pretty wide array of electrolytic cap sizes to fit into the holes.