Although the saying of caveat emptor rings loudly in the mind of any purveyor of electronic components, the lure of Very Cheap Stuff is almost impossible to resist. Sure, that $0.60 ADC on LCSC that swears it’s a Ti ADS1115 may be a knock-off since the same part on Digikey is $4 a pop, and that’s when you buy a pack of 1,000. Yet what if it’s a really good knockoff that provides similar performance for a fraction of the price? Cue [James Bowman] letting curiosity getting the better of him and ordering a stash of four boards presumably equipped with said cheapo knockoff part, mostly on account of getting all boards for a mere $2.97.
The goal was of course to subject these four purported ADS1115s to some testing and comparison with the listed performance in the Ti datasheet. Telling was that each of the ADCs on the boards showed different characteristics, noticeably with the Data Rate. This is supposed to be ±10% of the nominal, so 7.2 – 8.8 times per second in 8 samples per second mode, but three boards lagged at 6.5 – 7 SPS and the fourth did an astounding 300 SPS, which would give you pretty noisy results.
Using a calibrated 2.5 voltage source the accuracy of the measurements were also validated, which showed them to be too low by 12 mV. The good news was that a linear correction on the MCU can correct for this, but it shows that despite these parts being ADS1115 compatible and having features like the PGA working, you’re definitely getting dinged on performance and accuracy.
[James] said that he’s going to run the same tests on an ADS1115 board obtained from Adafruit, which likely will have the genuine part. Either way, if you are eyeing this ADC for your own projects, it pays to consider whether the compromises and potential broken-ness of the knockoffs are worth it over coughing up a bit more cash. As they say, caveat emptor.
And here I thought that lcsc is a reliable source for components, for jlc pcb assembly. Quite disappointing.
The counterfeit parts were sourced from Amazon. The article is assuming they’re the same as the LCSC parts but it wasn’t tested.
From the original article: “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.”
His test compares cheap breakout boards from Amazon with the more expensive option from Adafruit. LCSC has nothing to do with it.
It’s worth noting that the bad boards were actually from Amazon, which is known to sell a lot of knock-off parts. I think LCSC is at least trying to keep their supply-chain reliable and to mark clone parts as not being from the original manufacturer (no idea how successful they are at that).
I agree the price difference of DigiKey vs. LCSC for ADS1115 is substantial. It would be interesting to see a comparison against LCSC part and DigiKey part. Seeing that random Amazon sellers sell knock-offs is no surprise at all.
I do like to see an in depth analysis of the ADS1115, but a single ADC measurement (Even if it’s from a good voltage standard) does not mean much. How good is linearity over it’s full measurement range? What about drift over temperature and aging?
Also, comparing LCSC with ebay, amazon, aliexpress and all those other cheap chinese garbage outputs is not very useful. LCSC has a pretty good reputation, and if they claim to sell Ti parts, then I tend to trust those are Ti parts.
And apart from that, the “western world” is quite sick at the moment, with monopolies (or small group looking at each other’s prices) are all over the place. Ti itself lists the ADS1115IDGSR for USD2.1 (1k+).
There are a few threads about decapping IC’s and making die pictures on the EEVblog. It would be nice to see some “known good” parts compared with both LCSC and the chinese knockoffs.