AD584JN not starting

[jorgemef]

Hello.

I purchased from Aliexpress two AD584JN and two AD584KN.
The K version works normally. On the 2.5V setting one gives 2.49974v and the other 2.49985 read on a BM869s. Works even without capacitor.

I am using a LM7815 to provide regular voltage.

The J version is not starting at all. even with capacitor. Already tested Vin up to 25V but nothing, in any of the J version. The K version is like rock.

In the J version with 15V between VIN and Common, Vout pin reads 1.8mv, flickers around 0.76v in the 5V pin and in the 2.5v pin, cap pin voltage jumps between 2v and 5V, VBG voltage flickers around 0.22V and strob pin voltage flickers around 0.78V.

Am I doing something wrong or shall I toss the J version to the bin?
J version was 1.67€ each and K version 1.80€ each

Cheers,
Jorge

[modoran]

Just buy from a reputable distributor, not fakes from China which may work or not. Even if it works, it has nothing to do with original Analog Devices performance.

[magic]

Chinese roulette. Sometimes it's original chips, sometimes it's recycled chips, sometimes it's other recycled chips with modified markings, sometimes is some Chinese substitute with fake markings, sometimes it's a completely unrelated Chinese chip with fake markings. The only rule is that there is no rules. You either accept the rule, or you don't play the game at all, or you lose

Two chips on your breadboard look differently from the other two, could you post closeups with visible top markings? Good light helps a lot.

Before binning the chips, see this thread for a few fun ideas of what could be done with them. Noopy's articles are in German, but pictures are self-explanatory.

If they don't want to work as AD584, I would check if they work using ordinary DIP8 reference pinout. That is, ground at pin 4, input at pin 2, output at pin 6. Then check if they are NE555, opamps, etc, but this is quickly getting crazy...

edit
Crazy and likely to do permanent damage. BTW, are they getting hot when connected as AD584?

edit
I'm stupid
The first thing to do with an unknown chip, always, is to test all pairs of pins with a DMM in diode mode. Look for pins which have diodes from itself to most other pins - these are likely power supplies.

Since these are supposed to be AD584, and you have a good sample of AD584, test for diodes between pins and compare between the good and the bad samples. If you put red probe on common, you should see diodes to at least a few other pins. You should be able to detect several resistors between pins - see the internal schematic in the datasheet.

[jorgemef]

Hello,

The two good and the two bad. The shiny ones are the bad.

Will check with the multimeter the pinouts later today.

BR,
Jorge

[magic]

KN look dodgy. I think they had their original markings scratched from them. Does the top look differently (more scratched, grainy) than the other sides? I don't think Analog would print their logo partly on the polarity notch, that's a typical Chinese faker fail.

The shiny ones, are they also shiny on the sides and bottoms or only on the top?
If just the top, it means that their original markings have been scratched and then the top was painted black to hide the scratching marks.

[Gyro]

It's always a bad sign when the package molding profiles and surface finish are different. Looking at the first photo, the KNs look to be blacktopped too, rub the tops with Acetone and see if the black comes off.

[jorgemef]

The resistor networks do match for the K but nothing near for the J, so fake they are.

[magic]

The K are probably recycled chips too
As I said, and wasn't the only one, they look very suspicious.

But if they work, they should be mostly OK, I guess.

The J must be some other IC altogether. It happens on AliExpress quite often.
If you feel like finding out what they are, do the diode tests. Or just apply power to pin 2 and see what comes out on pin 6.
Or tear them down, or ask Noopy if he would like them.