Small teardown: an old TEK IC

[muvideo]

Hello, this is a small teardown, I'm thinking to replicate an old tek ic
from discrete components, it's a 155-0013-00, a logic ic containing
the equivalent of one T flip-flop and few gates.
I'm still figuring out the possible logic levels, someone on the TekScopes
mentioned that probably these ic are RTL logic.
I had one defective unit: it's working but doesnt follow correctly
the truth table, it's canned, so easy to open:


here is the chip


some close up view, changing the lighting shows 2 series of parallel lines,
at 90 degree. I dont know anything of IC technology, is it possible
to spot transistors and resistors, reverse engineer the schematic?
Near the Pin 7 there is also an odd track that probably can be the damaged
area.


This is the logic diagram of the chip:
http://www.flickr.com/photos/14336723@N08/7635785700/#

Fabio.

[amyk]

The metallic trace-like regions you're seeing are the metal layer. The faintly visible lines are probably polysilicon ("poly"), used either for general interconnects or as resistors. Some of the vias are also faintly visible. The poly layer will be under the metal layer. Adjusting the depth of field should make them more obvious, and you might be able to see the vias more clearly too. I'm not too familiar with bipolar stuff (used to CMOS, which can be very clear to decipher the FETs) but looking at the construction of a BJT the repeated structures I've outlined in the picture are probably transistors. The one near pin 7 does look damaged. I've also pointed out a few of the poly resistors. You'll need to get better die photographs and more info about the logic family used, pinout, etc. if you really want to recover the schematic. The visual6502.org site might have some samples of bipolar chips too in their image archives.

[muvideo]

Thank you amyk for the tips,
I have some info from the service manuals, this is the block
diagram of the IC:
http://www.flickr.com/photos/14336723@N08/7635785700/#
in that flickr albume there are some other images, one example
of in curcuit usage is here U2530 U2535 U2540:
http://www.flickr.com/photos/14336723@N08/7635785570/#

I know that Pin 5 is Vcc +5V
pin 2 GND
pin 9 is connected to the can so to the bottom of IC, in circuit it is tied to -15V trough a resistor
pin 6 is out
other pins are inputs.

Logic levels are not very clear from the schematic, some inputs are
directly connected to 0-5V, some others are connected to lower levels,
the output itself is annotates as 1V high level.

Is there a rule for the relative position of E B C regions of the
transistors? Or I should deduce from the schematic where is the
Base etc?

As for the image, I'm limited by my setup, but I think the lighting can
be greatly improved, in that image the lighting was from ambient,
and are visible vertical structures, if I light from another orientation
I can see orizontal features. Any tip for improving the features visibility is welcome.

Fabio.

[muvideo]

Another 3 images, I have a flare problem with the microscope.

[free_electron]

Looks like the metal coming from the corner wire into the transistor is toast ....

The 'line's you are seeing are the edges of underlying structures.
This chip is single layer metal, Bipolar process.

Here is a document that show how the transistors are built. You will recognize this shape immediately on the chip

http://users.ece.gatech.edu/pallen/Academic/ECE_4430/Summer_2004/L160A-BJTTech(2-UP).pdf

[muvideo]

Looks like the metal coming from the corner wire into the transistor is toast ....

In fact, observing visually trough the scope there is an area where the metallization is absent and there
are what seem small spheres, likely residue from a local fusion this would explain the behaviour of the chip.
It's fascinating to observe by eyes the actual ic damage.

The 'line's you are seeing are the edges of underlying structures.
This chip is single layer metal, Bipolar process.

Here is a document that show how the transistors are built. You will recognize this shape immediately on the chip

http://users.ece.gatech.edu/pallen/Academic/ECE_4430/Summer_2004/L160A-BJTTech(2-UP).pdf

Interesting, so the two pads that are closer should be base and emitter, the other more spaced
apart is the collector. Is there any hint of being npn or pnp? Seem that npn is simpler, is it possible
that the chip is made only of npn parts?

Fabio.

[SeanB]

PNP will have a diffusion ring around it, and will be slightly larger. Most likely all NPN, as high gain lateral PNP transistors are difficult to make, and were actively designed around.

[free_electron]

Yellow rectangles are transsitors.
Red circle is where it went 'boom'
Blue rectangles are resistors.

There is , what looks to be , a mulit emitter transsitor , possibly a current bias generator of some kind on the left ( green rectangle )
The dark blue structure is possibly a current reference. ( one transsitor with e/b shorted to act as diode steering another one )

[PA0PBZ]

although I agree that it is an interesting experiment it looks like you can buy the thing for $ 10,-
http://www.qservice.tv/vpasp/shopexd.asp?id=10781
http://www.ebay.com/itm/Tektronix-155-0013-00-155001300-Custom-IC-NEW-/140740075706

[muvideo]

although I agree that it is an interesting experiment it looks like you can buy the thing for $ 10,-
http://www.qservice.tv/vpasp/shopexd.asp?id=10781
http://www.ebay.com/itm/Tektronix-155-0013-00-155001300-Custom-IC-NEW-/140740075706

I know that this chip is an easy find, but the reverse is more fun

Fabio.

[amyk]

Try lighting with different colours and viewing more obliquely. That might be able to bring out some more of the detail.

[muvideo]

I will try to highlight better the edges, free_electron I was thinking
that B-E should be the two closer contacts, and C the one slightly far,
can you explain how you recognized the relative position?

Thank you.

[muvideo]

I took more images and applied a little of post process, now the edges are
a little better:

[amyk]

Great pictures. You can clearly see Q16's emitter connection is blown out and the residue that remains. It's RTL, all NPN. The -15V to the substrate is for reverse-biasing the parasitic diodes between it and each transistor (substrate is P, transistor's collectors are N wells, so there is a diode formed between them) to prevent them from conducting.

Q20 may have been purposely configured backwards.

I could derive the schematic and the gates from them. A quick simulation confirms that its operation matches the table in the manual. The actual gate-level schematic is a little different, 3 OR 4's output is used to reset the flip-flop too. I've labeled on the gate-level schematic the associated transistors for each gate, and the 4 flip-flop outputs with the resistor providing the pull-up on its node. The T flip-flop is the usual master-slave design.

Have fun trying to build a replica from discretes

[muvideo]

Thank you amyk, great work!

I made some better pics with tilted surface and different lighting:


This is the image sligtly enhanched:


This was my best bet, comparing with your reconstruction seem
that I nailed many of the features, but not all, and screwed b-e positions 


Fabio.

[muvideo]

amyk one thing I dont understand, yourself talked about blown Q16 (in your notation) emitter,
this connection goes straight to pin 7, but in your schematic pin 7 goes to Q16 base.
In my reconstruction Q16 base is connected to R20-R24 emitter to input and collector
to R20-Q15 base, is it possible?

[amyk]

I'd say it's not impossible, but in RTL inputs are usually connected to bases.

Emitters as inputs are a characteristic of TTL.