How reliable is the AMS1117 verses the LM1117? Please give your own experiences? - Page 1
Forum section: electronics / beginners

author: castingflame
author_rank: Regular Contributor
timestamp: August 09, 2020, 04:48:37 am
content: I have a project where I use LM1117 3v3 & LM1117 5v LDOs. I was thinking about substituting them for the much cheaper equivalent AMS varieties.Please give your own real world experience of if this is a reasonable change in part, performance, reliability, heat of the AMS LDOs.Nearly all of the Chinese clones and OEM Arduinos, FPGA dev boards, electronics modules, etc, that I have use the AMS range of LDOs so I know they are used widely but how do they 'stack up' against the LM1117s?I know that the LM1117 is rated as an 800mA device and the AMS is (Chinese) rated as at 1Amp but my requirements are only 200mA at most.Thanks for your advise.

author: ataradov
author_rank: Super Contributor
timestamp: August 09, 2020, 05:34:21 am
content: I never used them for full load, but at < 300 mA they worked fine for me, no complaints at all.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 09, 2020, 06:00:26 am
content: IMHO, 1117 is shit: all the downsides of old-school low-drop regulators, and massively high drop out in terms of today's low-drop regulators. AMS1117 is probably just fine vs. LM1117, but I'd consider replacing with something modern, better, smaller, cheaper with less stringent (and thus, less expensive) output capacitor requirements.I choose LDO regulators by looking at what's available on distributor websites, instead of going for the "everybody has used this for 40 years" parts, because unlike standard drop-out parts which were quite fine 40 years ago, LDOs have come a long way. If I don't need low drop out, I might just put an 78xx there (it has far better stability and capacitor requirement specs than 1117), and if I do need low drop out, I use a modern FET-based LDO.

author: ebclr
author_rank: Super Contributor
timestamp: August 09, 2020, 08:15:55 am
content: "but I'd consider replacing with something modern, better, smaller, cheaper"With one fits that ?

author: magic
author_rank: Super Contributor
timestamp: August 09, 2020, 08:24:35 am
content: 1117 have enough dropout for the very common case of making 3.3V from 5V and LM78 just wouldn't cut it. I think that's their primary application.The Chinese also became experts at running them with ceramic output capacitors without apparent stability issues.editAnd I wonder if there is only one company making them in China and if they are all identical, particularly if you buy from auction sites.For instance, the TP4056/TC4056 Li-ion charger ICs appear to be made by two Chinese companies and it's a lottery which one you get.

author: sleemanj
author_rank: Super Contributor
timestamp: August 09, 2020, 09:06:46 am
content: Be cautious with input voltage above 9v as some chinese AMS have low max input and will fail shorting input to output, so you end up with 12v on your 5v rail.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 09, 2020, 10:34:56 am
content: Here's a representative query:https://www.digikey.com/short/z5d0qwWithout filtering for dropout, it's all 1117 clones, starting at $0.36 in singles. (Price at 1000 would be more representative, but DK's pricing scheme is usually consistent so it's probably not a big deal.)So which is the bigger priority? Modern? Better? Smaller? Cheaper?Mind, unless you've making 1000 of something, price isn't very important, design and assembly costs are.Tim

author: Siwastaja
author_rank: Super Contributor
timestamp: August 09, 2020, 11:53:56 am
content: Add the cost of the 10µF tantalum, compared to the cost of 1µF MLCC. It's some $0.10 extra, at qty=1000, just for the cap. PCB area also has a cost, so does having an additional line in BOM just to satisfy the regulator. Running outside the datasheet recommendations is really not recommended. I have tried to push my luck with 1117 and really got them oscillate. LM1117 datasheet specified minimum ESR of 300mOhm and minimum capacitance of 10µF, and these are listed as requirements. IME, better satisfy them.For the question of "what is better, then", I already gave the answer: look at your distributor parametric search. The answer IMHO is anything that is stable with a small, cheap MLCC, say preferably 1µF, maybe 2.2µF. You likely have a 1µF MLCC in your BOM already, if you can use it (or put two in parallel), even better. If you have the regulator right next to the MCU for example, you can satisfy both regulator and the MCU bypassing by one ceramic. Fewer parts to place, easier design, easier assembly!If it requires as much as 10µF, or if it requires a series resistor or using a tantalum, then I won't use it, unless it has some other magical feature, like extra low noise, very good PSRR at high frequencies, or very good regulation. Which 1117 obviously do not have.For such sub $1 components, I look at the prices at 1000pcs or so. If you are just building 10pcs, the cost difference doesn't matter. But when you are looking at 100 suitable parts, you have to sort one way or another. When everything else is satisfied, I like to sort by price @ 1000pcs, that gives you an idea which parts are mass-market, and which are not. Mass market is good for availability, too! Cheap parts tend to have pin-compatible alternatives.Chinese designs tend to use components where the local availability of drop-in replacement or counterfeit parts is good. The reason for using 1117 may be that the cost for them might be closer to $0.01, and local availability is good. If you buy from Digikey, just look at the Digikey prices.Sorting by price, I findAP2138for $0.12 at qty=1000, and this is stable with a 1µF ceramic (min ESR is 10mOhm). But I didn't carefully look all the specs to see if it fits the OP's question. It satisfies 200mA current at least. The package is nice, small, yet easy to handle, but not very good at thermal dissipation so do the math.Having Vin(max) = 6.0V really widens your options. This brings you the cheap, modern selection made with the same CMOS process most modern ICs are made, some in very small packages. These parts are designed for things running at 5V, or from a single li-ion cell, have abs.max. somewhere around 7V and recommended max around 6V, and are fine if you have a regulated 5V bus available, with the usual filtering and damping in place.

author: mariush
author_rank: Super Contributor
timestamp: August 09, 2020, 12:14:38 pm
content: What are your other requirements, for example maximum input voltage?You said 200mA the most. I was about to suggest going with something like MIC5528 (500mA max, 0.5v dropout voltage) but it's maximum input voltage is 5.5v :https://ww1.microchip.com/downloads/en/DeviceDoc/MIC5528-High-Performance-500mA-LDO-in-Thin-and-Extra-Thin-DFN-Packages-DS20005982B.pdfThey're cheap, Digikey has them for 16 cents if you buy at least 25 ... in the 14 cents if you buy hundreds.It could still work, if you need 2 regulators and you already have 5v produced by other regulator.LD29150 is looking good if you a chip that can do up to 1.5A, it's in DPAK package so a bit better heatsinking, good voltage drop at 0.4v and it's 40 cents in volume....https://www.digikey.com/product-detail/en/stmicroelectronics/LD29150DT50R/497-3468-1-ND/669273I sometimes also look at the maximum quantity available, because what's the point if there's only 1000 in stock and next batch comes in six weeks and that chip may be hard to source from other placesFor example, Digikey has 115k pieces of TL5029 , which can do 500mA and handles up to 16v and can be cheap in volume (50 cents at 1000pcs)linkhttps://www.digikey.com/product-detail/en/texas-instruments/TL5209DR/296-21569-6-ND/1944842There's cheaper options , for example AP211H from Diodes Inc. (600mA max, 6v max input) is available in 82k units and is as low as 11 cents for 1000 pieces and you'd be able to easily find alternative chips with compatible pinout for it (it's sot23, easy footprint) .. linkhttps://www.digikey.com/product-detail/en/diodes-incorporated/AP2111H-3-3TRG1/AP2111H-3-3TRG1DICT-ND/4505138

author: castingflame
author_rank: Regular Contributor
timestamp: August 09, 2020, 12:41:33 pm
content: Great answers, and some really interesting points that I have not considered.Just to follow on with a little more info ...My input voltage is 9v and that feeds the 5v LDO. The 5V LDO then feeds the 3v3 LDO.Pricing maybe important as this application may well be for a few 100 boards so it has to be taken into account so the point that someone highlighted about having to use tantalum caps with these was very valid. ATM, I am using tantalum caps that cost approx 15p each (x3) so it soon adds up.I don't need the current requirements of a switching reg and I am very limited in space. The SOT-223 package was manageable size wise and had a decent area to sink heat into the PCB. Although I do not push these LDO, keeping them only just warm is also an advantage given where they are located in the case of the device.Going for a 'stock' older part may not be optimal design wise I completely agree but the availability does help availability wise.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 09, 2020, 01:09:30 pm
content: Note that you do not need an LDO to go from 9V to 5V. Standard drop out linear regulator is also an option. Widens your search, especially if you are looking for a low-cost old-tech mass-market classic.Especially in older-gen devices, standard-drop parts (1.5-3V drop-out) tend to perform better than low-drop parts (1-1.5V drop-out; that was "low" back then); for example, the classical 78xx series is stable with a very small output capacitance like 100nF.

author: castingflame
author_rank: Regular Contributor
timestamp: August 12, 2020, 08:16:06 am
content: Quote from: blueskull on August 09, 2020, 02:49:18 pmDo you have a link to LCSC please?

author: castingflame
author_rank: Regular Contributor
timestamp: August 12, 2020, 08:17:29 am
content: With your comments in mind, I will look at options for the 5v regulator.

author: janoc
author_rank: Super Contributor
timestamp: August 12, 2020, 09:37:35 am
content: In fact, if you are thinking about buying AMS1117 from China (eBay, AliExpress ...), you are most likely not going to get the genuine parts but one of the cheap "mostly-equivalent" Chinese regulators listed e.g. on LCSC. Except they have max. current like 150-200mA instead of 800-1000mA and similar ...

author: exe
author_rank: Unknown
timestamp: August 12, 2020, 10:11:18 am
content: My pick is LP5907 as it has good PSRR. It costs ~$0.26 in small quantities from lcsc. But input is limited to 6V max. Disclaimer: haven't tried this part yet. So, would love to hear some feedback about it. It was chosen for its performance vs price.If price really matters, check this:UP: it seems all ultra-cheap ldos are gone on lcscnope, I got sorting wrong.