How bad can a $2.97 ADC be? • Hacker News Board

Re: How bad can a $2.97 ADC be?

#21

Post by NoiseBert69 » Tue, Oct 14, 2025, 6:06 PM UTC

mindslight wrote: post #4

Err, 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.

Honestly: 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 I have access to our internal STM32 pricing. You'd be shocked.

Re: How bad can a $2.97 ADC be?

#22

Post by throwup238 » Tue, Oct 14, 2025, 6:07 PM UTC

q3k wrote: post #14

throwup238 wrote: post #7

> 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.

Interesting, 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…

I 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.

Re: How bad can a $2.97 ADC be?

#23

Post by lokimedes » Tue, Oct 14, 2025, 6:08 PM UTC

the__alchemist wrote: post #17

brcmthrowaway wrote: post #8

Has there been any updates on ADC technology? What does SKA/CERN use?

Curious too. The part in question has been around for a while.

My lazy answer is to search for ADC on https://cds.cern.ch

Re: How bad can a $2.97 ADC be?

#24

Post by 0l » Tue, Oct 14, 2025, 6:11 PM UTC

mindslight wrote: post #4

Err, 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.

LCSC is definitely genuine. I'm not sure why people are so surprised that companies like Mouser have insane markups.

Re: How bad can a $2.97 ADC be?

#25

Post by throwup238 » Tue, Oct 14, 2025, 6:13 PM UTC

NoiseBert69 wrote: post #10

I 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.

> 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)

Re: How bad can a $2.97 ADC be?

#26

Post by hex4def6 » Tue, Oct 14, 2025, 6:14 PM UTC

jamesbowman wrote: post #18

throwup238 wrote: post #7

> 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.

Author here. I did consider this, as others have reported getting ADS1015 marked as ADS1115. If it were an ADS1015 the readout would be truncated at 12 bits. These parts definitely delivered 16 bits of readout.

I worry about the demo boards being radically different in terms of layout etc. Even if you're using the same interface and power supply, the PCB may be affecting performance.

Getting full spec performance out of an ADC requires having good layout power supply routing etc.

I would transplant the chips from PCB A to PCB B and vice versa. See if the performance follows the chip or the PCB.

Also check power consumption before / after board swaps. If they are fakes, that would be significantly different.

Re: How bad can a $2.97 ADC be?

#27

Post by ZeroConcerns » Tue, Oct 14, 2025, 6:14 PM UTC

Well, 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...

Re: How bad can a $2.97 ADC be?

#28

Post by RobKohr » Tue, Oct 14, 2025, 6:15 PM UTC

ADC = 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.

Re: How bad can a $2.97 ADC be?

#29

Post by beachy » Tue, Oct 14, 2025, 6:15 PM UTC

I'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?).

Re: How bad can a $2.97 ADC be?

#30

Post by throwup238 » Tue, Oct 14, 2025, 6:18 PM UTC

jamesbowman wrote: post #18

throwup238 wrote: post #7

> 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.

Author here. I did consider this, as others have reported getting ADS1015 marked as ADS1115. If it were an ADS1015 the readout would be truncated at 12 bits. These parts definitely delivered 16 bits of readout.

Ah oops I missed that. Maybe an ADX111A then?