8 ms·
How bad can a $2.97 ADC be?
- isoprophlex 1y ago4x the price, at approximately 4x the error (12 mV instead of ~3 mV on the spec) Weirdly honest deal, haha.
- q3k 1y agoShould be easy to compare - sand down both the cheapo and a legit one (with a similar datecode) with fine sandpaper, clean with isoprop and shove under an optical microscope - you can then tell how similar/dissimilar the dies are, you don't even have to look for markings or anything super legible, or even sand them to the same metal layer. Clones tend to be vastly different - different technology node, architecture, die size, etc. - that's because they are generally functional clones, not mask clones. (also, as a general shoutout to the low tech sandpaper technique for exploratory work, here's a sanded down RP2350 thrown under a clapped out SEM: https://object.ceph-eu.hswaw.net/q3k-personal/484e7b33dbdbd914f6bb8974741b143cf727262205ecedf8152ce8d1935c35ba.PNG https://object.ceph-eu.hswaw.net/q3k-personal/484e7b33dbdbd9... https://object.ceph-eu.hswaw.net/q3k-personal/3290eef9b6b9adf78f909a673f84a9fea69741360e7012d77147c054ab8c8d7b.PNG https://object.ceph-eu.hswaw.net/q3k-personal/3290eef9b6b9ad... )
- cheschire 1y agoIt may not even be a clone. As the author said, it could just as easily be production line items that were tested and found to be outside of spec tolerances and resold off-label.
- q3k 1y agoWell, that's the point of the experiment, to figure out if it's a clone or a reject :).
- throwup238 1y agoTI makes all their analog stuff in house so that's unlikely. That's far more common for fabless companies that send their parts off to an outside fab.
- cheschire 1y agoWhat does TI do with their out-of-tolerance products? Straight in the garbage?
- throwup238 1y agoYes, though depending on the product line it may be binned into lower quality parts first. Remember though, the marginal cost of these chips is so small the packaging is usually more expensive than the silicon. They often get tested before the wafer is even sliced up so any waste is hardly worth mentioning until you get into modern processes with large error rates and huge chips like CPUs.
- 15155 1y agoTI isn't patterning $10000 wafers at 3nm with massive chiplets and questionable yield, they are making mostly commodity ICs on cheaper processes - they can afford to discard rejects.
- Lerc 1y agoI think the implied question is do they discard, or do they destroy. Discarded things tend to get lost. Lost things tend not stay in the Anduin forever.
- LeifCarrotson 1y ago> "Discarded things tend to get lost. Lost things tend not to stay in the Anduin forever." I'll have to put that on a warning label near our non-conforming-product containment shelf!
- pinkmuffinere 1y ago
- Hasz 1y agoI have done this a bunch of different times, mostly to resolve sourcing disputes. Dissolving in boiling sulphuric acid/nitric acid will make quick work of most epoxy packaging IMO, I have mostly seen mislabeling, rebinning, and passing off obvious QC rejects. example from many years ago: https://www.youtube.com/watch?v=e6DfBuPwAAA https://www.youtube.com/watch?v=e6DfBuPwAAA
- q3k 1y ago> Dissolving in boiling sulphuric acid/nitric acid will make quick work of most epoxy packaging That's the better method of course (results wise), but it's not nearly as accessible, hence my recent evangelism of the virtues of 2000 grit sandpaper.
- jacquesm 1y agoI like it. I've used sandpaper to solve some interesting problems in the past as well with great success. I suspect we are only seeing the beginnings here in a trend of high-tech applications of fine grit paper.
- Terr_ 1y agoI expect it's much easier to acquire fine sandpaper, yet my inner child yearns for laser decapping. (Or I suppose more than "decapping", depending on the depth.)
- jacquesm 1y agoHigh power lasers are becoming more and more affordable. Laser ablation is definitely an option but you really want to have some proper fume extraction around that.
- BertoldVdb 1y agoLaser decapping will destroy the die, except if you have a rare package that does not mix glass in the epoxy. You could still compare the internal structure of the package and bonding, but the die itself is mostly destroyed.
- fullstop 1y agoI don't know if we can ping people here, but this looks like something that would be right up Ken Shirriff's alley. 1. https://righto.com https://righto.com
- mindslight 1y agoErr, the title isn't really correct. The genuine part is still only $4. This is a 60 cent knockoff. Not having done design in a while but still having a rough feeling for costs I was a bit confused.
- NoiseBert69 1y agoHonestly: no one of the bigger players in the industry pays the prices you see on Digikey/Mouser/Farnell (with the exception maybe for prototyping stuff). Often you have direct delivery contracts with the vendors. That the ADS1115 costs <$1 on LCSC means they buy millions from them every year. They are one of the biggest trustable players in Asia. I have access to our internal STM32 pricing. You'd be shocked.
- the__alchemist 1y agoH7s for <$1? I get confused whenever people talk about paying $0.69 for an MCU!
- squarefoot 1y agoI recalled a few years ago there were shockingly inexpensive MCUs at LCSC and similar far east vendors, but they were never heard before names, so I just checked again out of curiosity and here's a $0.05 one by Cypress. https://www.lcsc.com/product-detail/C2954567.html https://www.lcsc.com/product-detail/C2954567.html
- NoiseBert69 1y agoI played around with the RISC-V from WCH. They are huge step ahead: the upcoming CH32H417 has pretty much all PHYs integrated (!). For 10/100M Ethernet, USB-C 5GBbps and USB HS 480Mbps. That dramatically reduces the components needed to get that stuff running. I also build a small robot with the ultra cheap CH32V003. That's a full fledged 48MHz microcontroller with 16kb flash and 2kb SRAM. Fun little thing. If you are used to the ST HAL you will be able to work with them within 10 minutes. Their API style is similar.
- throwup238 1y ago> So what’s going on with the cheap parts? My best guess is that these are either quite good copies, or failed parts that somehow made their way into the hobbyist supply chain. The vast majority of counterfeit chips I've seen were from ghost shifts but IIRC TI fabs all their analog parts in house, I doubt they're ghost shift parts or failed QC. I think its probably a relabeled ADS1015.
- q3k 1y agoInteresting, most of the counterfeits that affect me (eg. FTDI, STM32 clones) have been just straight up clones developed from scratch, not excess inventory / ghost shifts / packaged rejects. I guess it might be a digital/mixed-signal split, with the two worlds having different issues? (also interestingly the STM32 clones I've seen had stacked die flash because they didn't fab them in a technology that could also do flash, so you can easily tell the counterfeit from sanding down the package and looking for an extra set of bonding wires; it's also a cool place to access the internal flash bus if you wanna bypass some readout protection :) )
- throwup238 1y agoI remember the mess with FTDI clones back when I was still a hobbyist and buying stuff from eBay, but ever since I’ve started doing EE professionally I rarely run into anything that bad. You’re not going to make a clone Marvell processor for example, but I’ve run into several ghost shift runs from a distributor. I don’t usually buy from electronics markets in Shenzhen either so that probably helps.
- londons_explore 1y agoBuy in bulk from the Shenzhen markets and sellers will be pretty clear that you're getting a clone, and will give you samples of that specific clone so you can QA your product with them. (Some popular devices have multiple clone suppliers). I now always buy clones where possible - whilst not all features are implemented and some specifications won't be met, the devices seem to match the original for reliability, and sometimes even come with their own cloned modded datasheet.
- brcmthrowaway 1y agoHas there been any updates on ADC technology? What does SKA/CERN use?
- the__alchemist 1y agoCurious too. The part in question has been around for a while.
- lokimedes 1y agoMy lazy answer is to search for ADC on https://cds.cern.ch https://cds.cern.ch
- willis936 1y agoWell, if you're trying to measure DC extremely accurately the old stuff is still golden. Multi-slope is the gold standard and no one will sell you one. Delta-sigma get most of the way there. https://youtu.be/upTgM_S5rAQ https://youtu.be/upTgM_S5rAQ And if you want to see CERN's multimeter, check this out. https://youtu.be/D28uSzCs7-k https://youtu.be/D28uSzCs7-k Marco Reps is a treasure.
- shadowpho 1y ago>Multi-slope is the gold standard and no one will sell you one. Why not?
- willis936 1y agoThe delta-sigma is conceptually very similar and gets you most of the way there for DC performance, but can be used for sample rates in excess of 100 kSamp/s. Multi-slopes also need large passive values that make an integrated solution impossible. Keysight will still sell you their 3458A. Also, the AD7177-2 exists. That might be evidence enough for delta-sigma's victory.
- NoiseBert69 1y agoI still have a huge trauma coming from the ESP32 ADC. Why don't they integrate good ADCs? We are waiting for ages now. Non-linear as hell - and evil side effects once you use the calibration curves.
- throwup238 1y ago> Why don't they integrate good ADCs? There are a bunch of reasons but the primary reason is that good ADCs are made using a different mixed signal process than microcontrollers. MCU ADCs are capacitive charge-balancing successive-approximation type which limits their sensitivity and precision. Standalone ADCs also eliminate significant sources of noise like temperature fluctuations and electronic noise (the digital logic on the chip often runs at less than 1Mhz for example)
- 15155 1y agoStandalone ADCs are often SARADCs as well (and are specified as such.)
- throwup238 1y agoThe ones I’ve used were mostly delta sigma modulation ADCs. I think charge balancing caps out at 12 bits or so.
- chillingeffect 1y agoIf hate the esp32 adc, let me introduce you to its "fpu." Or its external flash and memory...
- NoiseBert69 1y agoBut no real competition for on-chip Wifi/BLE around. Only ugly two-chip solutions or hyper exotic stuff with no community.
- bsder 1y ago
- byran 1y agoThe price difference could be explained by LCSC purchasing in bulk directly from TI or similar and selling them at lower margins because their volumes are larger. I've seen "clone" chips sold at LCSC, but they're listed under a different brand (I can't recall one off memory unfortunately).
- NoiseBert69 1y agoNever had bigger issues ordering from LCSC. And I buy a lot of stuff from them.
- deleted 1y ago[deleted]
- MountDoom 1y ago> These are cheap, relatively fast, and not particularly good. While they sport impressive-sounding 12- and 16-bit readouts, the effective number of bits (ENOB) is usually around 8 or 9. I don't think that's quite accurate for reasonably modern MCUs. You can typically shake 10+ bits out of them, but you need to take a lot of precautions, such as providing very stable external reference voltage and shutting down unneeded subsystems of the chip. They're still not as good as standalone ADCs, but they're at a point where you can actually use them for 90% of things that require an ADC. In cases where you need more bits, there's a lot more that must go into the design, which is what gives me a pause about the article. There's nothing about the PSU the author is using or how he managed the MCU noise and RFI. So I don't know if the findings here are that these are knock-off devices with worse specs, or if his overhead LED lamp is causing a lot of interference.
- magicalhippo 1y agoI tested a few STM32F103 dev boards, using a Siglent SDM3055 multimeter and Siglent SPD330X power supply. The chip has a 12bit SAR ADC. Layout and board design mattered a lot, but even the worst ones had 10 bits worth, and the best one had nearly 12 bits effective. That was without doing too much on the software side, meaning the other modules weren't running, besides a single serial output. On the bad boards the serial affected it, but on the good board very little.
- parsimo2010 1y agoI think you might both be right- the author may be thinking of lower cost MCUs only aiming for tolerable ADC performance, while you might be thinking of all MCUs, even higher cost. The RP2350 has 9.2 ENOB on a 12 bit ADC. Sure, you might be able to decimate multiple samples to get more bits out of them, but the spec sheet supports the author's claim (https://www.raspberrypi.com/documentation/pico-sdk/hardware.html https://www.raspberrypi.com/documentation/pico-sdk/hardware....). There are even lower cost MCUs like the CH32V003 that have even worse ADC performance. On the other hand, some MCUs can definitely do 10+ bits, such as the STM32H7 line which gets 13+ ENOB from a 16 bit ADC. This is impressive, but the H7 MCUs are literally an order of magnitude more expensive than the RP2350, so they might not be something the author tinkers with much. https://www.st.com/resource/en/application_note/dm00628458-getting-started-with-the-stm32h7-series-mcu-16bit-adc-stmicroelectronics.pdf https://www.st.com/resource/en/application_note/dm00628458-g...
- the__alchemist 1y agoOoh this is interesting! I've seen some big price differences between Digikey and LCSC at small volumes; not sure! You can also sometimes buy direct from TI. Of interest from early in the article: I'm curious how these external ones compare to onboard, e.g. STM32's. Btw, the TI one listed is actually pretty simple to use in comparison. The ST integrated ones have more config and hardware considerations, e.g. complicated calibration procedures, external VREF (mentioned) etc. So, if you do app the config, is the integrated one as good? The integrated ones usually have nice ways to integrate with timers and other onboard periphs.
- ZeroConcerns 1y agoWell, I guess a whole-three-genuine-US-dollars is actually pretty expensive for an ADC, and that the person-in-charge-of-your-BOM in one of the countries that can actually still manufacture things can get one for way less than that. Does it work? Well, does your design power up during factory testing, and then pass whatever things your rig (hope you made a few!) has in mind? Well, then, yes, in fact it does...
- LeifCarrotson 1y agoThese numbers add up fast when you have dozens or hundreds of components on your board. A $3 part is often one of the most expensive items on a board! If you're trying to get something shipped to consumers for $20 each, with an enclosure, packaging, shipping, retail markup, and profit...that's a huge price disparity. Also, and perhaps more importantly, the test rig is a lot simpler and a lot cheaper if you can generally trust manufacturer data. Sure, send off a few samples (likely prototypes with parts from Digikey instead of LCSC) to run extended testing in an environmental chamber with thermal imaging, build an endurance test rig that pushes the button once a second for four weeks to simulate once-daily use for years, whatever you want to do...but after that, if TI says it's good from -40 to +125, you're going to trust them on a lot of the edge cases. Do 100% testing of the things you can test in-circuit if you can - power it up at room temperature and make sure it works once - but that doesn't mean you get the actual rated performance across all published environmental conditions.
- RobKohr 1y agoADC = Analog to digital converter Takes an analog signal from something like light or sound and convert it into a digital signal. Acronyms introduced in an article should be spelled out at least once please.
- slices 1y agoI thought they were talking about League of Legends players, whoops
- clw8 1y agoFor regular readers of this blog, that would be like defining USB for a general tech audience. Other articles by this author expect the reader to also know terms like I2C and SPI.
- ted_dunning 1y agoMost readers of this blog probably still can't define USB beyond "what you get when you stick this kind of cable into that kind of hole in your computer"
- beachy 1y agoI'd like to know more about the world of ADCs. I've used the ADS1115 with success but only at very slow speeds. On the current project we started with an MCP3208 via SPI. It did the job but only has 8 channels and it's slow (100K samples per sec). To get something faster we switched to ADS7953. It has 16 channels and runs 10 times faster. It's somewhat more complex to code, and you can only get the highest sample rate if you scan the inputs in a predictable order. But it sure flies. To me, these chips feel like cars. The ADS7953 is somewhat of a ferrari, whereas the MCP3208 feels like a Toyota, simple to use, unimpressive performance. I'd love to know the industry background about how these varieties of ADC chips came to be and carved their own space in the world, and how widely they are used (millions? billions?).
- magicalhippo 1y ago> To get something faster we switched to ADS7953. It has 16 channels and runs 10 times faster. I recall reading about a project at CERN to design a 12bit ADC chip that could sample at tens of GHz, maybe 50 or more. I was perplexed at how they could achieve this. Turned out it was the same we programmers do. Parallel processing. They had taken a 12bit SAR unit which ran at like MHz rates, and just cloned it many times. They then had a large analog multiplexer in front to route the signal to the active ADC unit in a round-robin fashion. That takes a lot of chip real-estate, and the analog muxer had to be carefully designed. For a simpler approach to speed there is Flash ADCs[1], which kinda brute-force it. For precision I know multi-slope ADCs[2] are often used. Sadly I don't know much about the history, and would also love to learn more about it. Bound to be some fascinating stories there. [1]: https://en.wikipedia.org/wiki/Flash_ADC https://en.wikipedia.org/wiki/Flash_ADC [2]: https://www.analog.com/media/en/training-seminars/tutorials/MT-027.pdf https://www.analog.com/media/en/training-seminars/tutorials/...
- cycomanic 1y agoYou can buy ADCs at over 100 GS/s (keysight, teledyne and tektronix make oscilloscopes using them), however typical ENOBs are more around 5 bits for these. For people interested in this stuff, I there is a video of someone taking apart one of the high speed keysight scopes (I think signal path is the YouTube channel?).
- dazhbog 1y agoDigikey's markup is the issue.. most people in Asia buy from lcsc or agents, that can get parts 2-10 times cheaper.. In this case both parts are genuine just different batch/year/production location probably..
- metaphor 1y agoBullshit. LCSC is a grey market distributor whose sources of supply are of untraceable, dubious provenance. They are neither ECIA member nor participating distributor.
- a-dub 1y agoi wonder if the clock performance is worse too...
- cushychicken 1y agoOP is making comments about poor performance single cycle of a sigma delta ADC. Single cycle readings defeat the point of sigma delta ADC setups. You're taking many high noise samples and averaging them over time to get a better picture of the average voltage.
- LeifCarrotson 1y agoOP is using the chip with the data rate set to 8 samples per second. Natively/internally, it runs at 860 samples per second, and you can configure it to provide that data at a lower sample rate at lower noise levels by averaging multiple readings together internally.
- Aurornis 1y ago> Single cycle readings defeat the point of sigma delta ADC setups. The ADC's internal delta-sigma ADC takes a lot of samples at a much higher modulation frequency and presents them as a single output value. You do not get the direct delta-sigma output from an ADC like this. The internal logic handles that for you. It's okay to take single samples of the output.
- zsellera 1y agoMost companies have region-specific price lists. My Spotify subscription costs about 60% of what the same plan costs in the US (2200 HUF vs. 11 USD). In the electronics industry, everyone has a separate price list for China. Btw. the western list price is just an indicative at-most number anyway. Even a small-sized project gets discounted prices when you start talking to a sales rep.
- torginus 1y agoWhy would it be bad for that price? Highly accurate ADCs are pretty easy to make, provided you don't need a high sample rate, thanks to the magic of signal processing. Delta-sigma ADCs, and ramp ADCs can use a single bit of digital input + some pattern hold circuitry to do incredibly accurate measurements, it's just they take some time. If you want a flash ADC that can do 16 bit (and can do 16 bit at 100Mhz), however you'll have to probably mortgage your house.
- DrewADesign 1y agoI thought I sucked at debouncing until I tried a rotary encoder that wasn’t like 10 for $4 on aliexpress. Lesson learned. Then I found out they sell a lot of decent related stuff at Micro center.
- ycui1986 1y ago$3 ADCs are not cheap ADCs. Cheap ADCs are the one embedded inside cheap MCU. These days, TI sell cheap ADC/DAC that is artificially limited to 10/12-bit, but with linearity at more than 16-bit. The cost of producing bad ones versus good ones are not much different. They go through the same semiconductor process. So long as the fundamental design is sound, cheap ADC don’t perform any worse.
- reader9274 1y agoIf these are genuine TI parts, I highly suspect the issue to be a measurement error by the user. Whether it's $0.60 or $4 does not matter, that's due to the order size as mentioned in the article.
- celestivoxLab 1y agoWhen an ADC costs less than a cup of coffee, you might need some sandpaper to find out what's really inside.
- bob1029 1y ago> These are cheap, relatively fast, and not particularly good. While they sport impressive-sounding 12- and 16-bit readouts, the effective number of bits (ENOB) is usually around 8 or 9. The edge case of the 1-bit conversion scheme used in SACD format is compelling from a few perspectives. The idea is to run the sampling rate in the megahertz region. SACD achieves 120dB of dynamic range with an extended frequency response up to ~100kHz. CD audio only achieves 96dB of range up to 20kHz with its 16-bit PCM scheme. From the analog hardware complexity standpoint, a bitstream converter is much simpler than a multi-bit converter. The 16-bit ADC might be cheaper due to the insane manufacturing volumes. Trading bit depth for sample rate is a very compelling offer in many cases. The 3d graphics version of this is SSAA where you sample more pixels than your monitor needs in order to resolve higher frequency information. https://en.wikipedia.org/wiki/1-bit_DAC https://en.wikipedia.org/wiki/1-bit_DAC https://en.wikipedia.org/wiki/Direct_Stream_Digital https://en.wikipedia.org/wiki/Direct_Stream_Digital
- dazhbog 1y ago"I picked up breakout boards from Amazon for $2.97 if you buy four, and I very much think these are made with the $0.60 parts from LCSC or similar." There you are. Assumptions. Nothing to do with LCSC.
- rogerallen 1y agoFollowup here: https://excamera.substack.com/p/the-great-ads1115-pricing-mystery https://excamera.substack.com/p/the-great-ads1115-pricing-my... And here: https://news.ycombinator.com/item?id=45658163 https://news.ycombinator.com/item?id=45658163
- rasz 1y agoWeird follow up without apologizing for smearing LCSC with no evidence whatsoever. Imagine someone writing a blog post like "LLMs produce AI slop on regular basis. This piece of code I found somewhere on the web sure is AI slop, I never saw any code by James Bowman but _I very much think these are made with the_ AI slop generators _or similar_". And the follow up is "Remember James Bowman? _I’m still curious about_ his code. I might look at it in something or other at some undetermined point in the future to see how it performs." Does that sound even remotely ok? Its not even guilt by association. Its guilt by gut feeling? prejudice?