Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

How bad can a $2.97 ADC be?

excamera.substack.com

Post reply on HN
Print view View original

91–100 of 141 posts

Re: How bad can a $2.97 ADC be?

#91

Post by ryukoposting »

MountDoom wrote: post #15

> 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 unnee…

Glad I wasn't the only one thinking this.

The paragraph ending with "Compare that with a microcontroller ADC with a fixed 3.3 V range: 9 ENOB steps are ~6 mV" also seems to insinuate that no MCU has an analog reference that's independent from the supply, which just isn't true at all. Hell, NXP has a few that have a built-in programmable reference.

Re: How bad can a $2.97 ADC be?

#92

Post by Tade0 »

q3k wrote: post #43
Hasz wrote: post #42

Earlier quoted context omitted.

I 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

> 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.

There was a sandpaper expert in that company associated with sour-tasting fruit which shall not be named. I believe you guys have met, though I think by that time he already pivoted to making the perfect cheesecake.

Re: How bad can a $2.97 ADC be?

#94

Post by q3k »

throwup238 wrote: post #76
q3k wrote: post #43

Earlier quoted context omitted.

> 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.

I prefer Japanese sharpening stones or those DMT diamond whetstones. It’s relative easy to 3d print a jig that converts a woodworking honing guide into an IC holder and you get a feel for how many passes to do very quickly before slowing down and checking each pass.

That's a super interesting idea! I'll also have to try that.

Re: How bad can a $2.97 ADC be?

#95

Post by userbinator »

NoiseBert69 wrote: post #58
chillingeffect wrote: post #31

Earlier quoted context omitted.

If hate the esp32 adc, let me introduce you to its "fpu." Or its external flash and memory...

But no real competition for on-chip Wifi/BLE around. Only ugly two-chip solutions or hyper exotic stuff with no community.

I'm not sure about WiFi, but JieLi (JL) definitely has a huge marketshare for single-chip BLE/BT. They are the origin of the infamous "the Bluetooth device is ready to pair" stock prompt voice.

Re: How bad can a $2.97 ADC be?

#96

Post by mikewarot »

15155 wrote: post #33
cheschire wrote: post #12

Earlier quoted context omitted.

What does TI do with their out-of-tolerance products? Straight in the garbage?

TI 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.

Not only that, leakage goes way up as you shrink the transistors, an ADC on a 3nm wafer would require a complete redesign, if it could be made to work at all.

Re: How bad can a $2.97 ADC be?

#97

Post by metaphor »

dazhbog wrote: post #44

Digikey'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..

Bullshit.

LCSC is a grey market distributor whose sources of supply are of untraceable, dubious provenance. They are neither ECIA member nor participating distributor.

Re: How bad can a $2.97 ADC be?

#98

Post by AlotOfReading »

NoiseBert69 wrote: post #58
chillingeffect wrote: post #31

Earlier quoted context omitted.

If hate the esp32 adc, let me introduce you to its "fpu." Or its external flash and memory...

But no real competition for on-chip Wifi/BLE around. Only ugly two-chip solutions or hyper exotic stuff with no community.

Not sure I'd call the silabs chips hyper exotic. The SIWG917 is intended as a direct competitor to ESP32s. It's a bit more expensive, but not unexpectedly so.

Re: How bad can a $2.97 ADC be?

#99

Post by ycui1986 »

$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.

Re: How bad can a $2.97 ADC be?

#100

Post by cycomanic »

Junk_Collector wrote: post #87
cycomanic wrote: post #53

Earlier quoted context omitted.

You 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?).

I think you are thinking of this video: https://www.youtube.com/watch?v=DXYje2B04xE

Yes thank you!
Post reply on HN