[YZF]

Ha. Right, as the article says with linear regulators unlike switching regulators all the extra energy ~(Vin-Vout)*I goes out as heat... They're so easy to use though. It's interesting someone would counterfeit them, so cheap and probably not as popular as they used to be back in the day...

[dfox]

They are so popular that almost every linear-IC manufacturer manufactures something that is drop-in replacement for 7805 (and usually calls that 7805, although sometimes other part names are used, i.e. that "2805" on the die shot in article. I vaguely remember that NEC uPD2805 is 5V linear regulator with same pinout as 7805).

Between different manufacturers there is easily an 10x difference in price of 7805, so counterfeiting is certainly worthwhile, even more so when 7805 is more of a description of function than of implementation. 7805 means three-pin linear regulator with dropout <= 2V, such and such accuracy, line/load regulation and noise and typical design uses these parameters, not actual parameters guaranteed by given name-brand manufacturer (which are sometimes significantly better than for original LM7805), so mostly no-one will notice if you take random Chinese 7805 and repackage it into name-brand package.

[YZF]

It's probably <<10 cents in quantity though and most mass produced electronics would use something smaller or more efficient (well, it has to be more efficient if you want to go smaller) if they even use a linear regulator at all. What would the total world wide market for 7805 be today? A few million parts a year? As a counterfeiter you'd have a few % of that market? Maybe worthwhile as part of a larger counterfeiting operation if you have the flexibility to make a lot of different chips in a lot of different packages but investing a lot of engineering effort in this specific single chip is almost certainly not worthwhile.

[sitkack]

Why silkscreen your own brand when could silkscreen ST or National? I could move a whole lot more Nike than I could Mercury.

[kens]

I'd really like to know if you have info on a "2805" regulator. I couldn't find anything about a NEC uPD2805. All I could find is a NJM2805 regulator, but it's a totally different 5-pin regulator.

[dfox]

I will try to look into it more, but I too haven't been able to find anything conclusive.

What I know, is that about 5 years ago I have found part marked NEC uPD2805 (or maybe 2905) in power supply for Canon fax machine and somehow found out that it is 7805-esque voltage regulator and used it in my bench power supply as such.

[MarcScott]

We use them in every circuit we build with our students. Most of our circuits use PIC chips and students have a habit of trying to chuck 12V through the things from their power supplies. Cheaper to add 7805s than constantly replace burned out chips.

[jevinskie]

Linear regulators are also ideal for low noise applications.

[CamperBob2]

Although not so much the 78xx parts. They're among the noisiest, by a couple of orders of magnitude.

[dfox]

But still, one of the most common applications for 78xx regulators outside of hobbyist and one-off applications is local regulation for some analog-ish noise sensitive-ish circuitry.

[raverbashing]

Yeah, still, if they're too hot to touch I believe it's being misused in the circuit (either missing a heat sink, or too much voltage drop across, or the circuit needs something more powerful)

But of course, this happens a lot in experimental circuits.

[agoetz]

Not necessarily. The LM7805 has a maximum operating temperature of 125C, so a circuit can be operating nominally at a very high temperature.

[VLM]

Actually thats the junction temp so unless you have an infinitely thermally efficient package and heatsink, if you're boiling water the innards are way out of spec.

Also check out the temperature derating curves.

That series has a thermal shutdown ckt so "operating nominally" above boiling pt is kind of hard to define.

There are also non-regulator thermal issues, like most cases are not designed to operate continually at 125C internal temps, and the electrolytic caps nearby the reg have their lifetimes drop with some polynomial of temp above room temp so smoking hot reg isn't good for everything nearby even if isolated by itself it would be OK.

Finally the general idea is still true, that you can get a nice 2nd degree burn or think something is "really hot" at a temp well below rated.

There are plenty of high power transistors rated to 150C junction temp. Not impossible with a really good package and heatsink (low thermal resistance) and good assembly technique to be able to boil water on one of those. As a stunt in the lab everyone tries this sooner or later to see if their anti-thermal runaway ckt is good enough and their assembly technique is good enough.

[VLM]

"(either missing a heat sink, or too much voltage drop across, or the circuit needs something more powerful)"

Starting in the 80s Low Drop Out LDO regs started hitting the market, using mosfets as the pass transistor instead of bipolar trans (and a few other changes) means you can run with much lower voltage drops.

However, legendarily, the bipolar voltage drop automagically provided some oscillation dampening and the LDO regs are notorious for being unstable, almost as much of a PITA as using a switching reg, almost. So sometimes with reactive (usually inductive) load at certain currents and voltages, they turn into little RF oscillators. Sometimes the oscillation is too high of a freq to interest the overheating and other self protection ckts so they literally catch fire and so on.

These 80s stereotypes of LDO regs have been continually improved since the 80s so they're somewhat more stable now.

Part of the shocker of both the bad 7805s in the story and the oscillating 80s era LDOs is the 7805 series used to be legendarily bulletproof because they have a lot of self protection circuitry built in. Blowing one up is non-trivial compared to most other chips. Usually decent reverse current protection, some reverse polarity protection, overheating protection, short ckt protection, they're pretty touch chips, so its surprising when they aren't.

[raverbashing]

Ah very interesting story, I didn't know about those LDO problems.

I guess BJTs at that power level are slow, as opposed to mosfets, which are much faster, so there's that as well.

[Alupis]

It's an interesting notion to "counterfeit" a chip... I mean, the supposed counterfeit still has to perform the same duties as the "legit" chip does... maybe of less quality, stability or longevity... but nonetheless, it does the same job. It's like saying Hyundai is counterfeit cars because their quality is less than Honda or something.

[jpindar]

Not at all. There are plenty of counterfeits that are not functional - some don't even have a die in them.

Also, these parts have a brand logo on them, but are not made by that manufacturer. If Hyundai sold cars with the word Honda and a Honda logo on them, without permission from Honda, they would indeed be counterfeits.

[sitkack]

Counterfeit items may also have higher quality than the thing they are pretending to be. Pretending something it is not w/o permission.

[DigitalJack]

counterfeits may not have the same tolerance specs, may not perform any special features (i.e. the shutdown control in over voltage conditions), may have spying functions (counterfeit cpu for example).