[time-nuts] A look inside the DS3231

[Graham / KE9H]

Yes, I doubt that the volume on a specialty chip like the DS3231 is high
enough to attract the counterfeiters.

RS-232 chips and the FTDI USB to serial chips, and consumer FM tuner and
audio amplifier chips, is another story.

My experience was with a proprietary full custom IC that totally
implemented a 'pager' in a single IC package. The Chinese apparently wanted
to get into the the paging business, at the time.  Of course, the
cellphones have now totally eaten the pager business, globally.

--- Graham

==

On Thu, Jul 27, 2017 at 8:21 PM, Pete Stephenson <pete at heypete.com> wrote:

> Graham,
>
> That's very true!
>
> Still, my past experience with copied chips typically involves a
> particular type of RS-232-to-TTL serial converter, the MAX3232. I've
> found that nearly all of the ones from unauthorized distributors (e.g.
> auction site vendors) are fake, even though the package is marked as
> being MAX3232. After a few weeks the chips would fail in a way that
> they'd pass high currents and get extremely hot.
>
> I did a write-up on those chips at
> <https://blog.heypete.com/2016/09/11/investigating-fake-
> max3232-ttl-to-rs-232-chips/>
> and, after decapuslating them, discovered they were completely different
> chips on the inside that were made to function the same way as the
> MAX3232 (i.e., they converted RS-232 signals to TTL serial, operated on
> the same voltages, had the same pinout, etc.).
>
> In regards to the DS3231, I was concerned that the chip was also a fake
> that functioned in the same way as the DS3231, presented the same
> registers to the user, etc., but was actually a different design on the
> inside. It appears that this is not the case, and in addition to
> functioning as advertised, it also is legitimate. If it is a clone, it's
> a goood one, but I don't think it is.
>
> Cheers!
> -Pete
>
> --
> Pete Stephenson
>
> On Thu, Jul 27, 2017, at 10:34 PM, Graham / KE9H wrote:
> > Pete:
> >
> > If you are concerned about someone copying a chip, you can not rely on
> > the
> > original manufacturers' markings on the die.
> >
> > I have experience where the counterfeiter just photocopied the chip
> > layout,
> > including the original manufacturers marks, and copyright symbol and
> > notice
> > from the original die.
> >
> > So, when they copied the die, they really just copied it. Didn't change a
> > thing. It was not like they redesigned it, or were selling their own
> > design
> > with equivalent functionality.
> >
> > --- Graham / KE9H
> >
> > ==
> >
> >
> >
> > On Thu, Jul 27, 2017 at 2:31 PM, Pete Stephenson <pete at heypete.com>
> > wrote:
> >
> > > Hi all,
> > >
> > > A few days ago I reported the results from letting a DS3231 RTC run for
> > > a year, and how the chip kept time well within the published specs.
> > >
> > > Since I had acquired several DS3231s from dubious sources (Asian
> vendors
> > > on a major auction site) as part of an RTC module that fits on the
> > > Raspberry Pi's header pins, I was doubtful of the authenticity of the
> > > chips. I decided to sacrifice one in the name of science and decapped
> it
> > > at home using alternating heat (a lighter) and cold (a glass of cold
> > > water) to embrittle the epoxy casing, then sanded down the back of the
> > > chip on fine-grain sandpaper to expose what I hoped was the back of the
> > > internals (so as not to damage the die itself).
> > >
> > > Other than inadvertently sanding through half of the crystal's housing,
> > > thus breaking one of the forks of the crystal, this was a success. (I
> > > was prepared to decap one in acid had my attempt at physically removing
> > > the epoxy package failed.) I slightly scratched the die itself while
> > > separating it from the epoxy, but the die itself is clearly visible.
> > > Based on a sample size of one and the markings on the die itself, it
> > > appears the chip is authentic. The markings on the outside of the epoxy
> > > package look a bit dubious and not like typical Maxim laser-markings,
> so
> > > it's possible the chip was re-labeled at some point. I'll contact Maxim
> > > to see if they can look up the lot information.
> > >
> > > I used my 2 megapixel USB microscope to take some images throughout the
> > > process that you might find interesting. The microscope has limited
> > > resolution, particularly at high magnification, so some of the photos
> > > may not be perfectly clear. I have access to a Zeiss petrographic
> > > microscope at my work and will see if I can get some better images
> > > tomorrow. I'll try to get high-quality images of the whole chip and
> > > stitch them together into a larger composite.
> > >
> > > Anyway, the photos are available at http://imgur.com/a/0zudj -- I will
> > > add more photos from the petrographic microscope tomorrow. I focused
> > > mainly on the markings on the die that indicated it was, in fact, a
> > > Maxim chip but if there's any other region of the chip that you'd like
> > > images of, please let me know and I'd be happy to take some more
> > > pictures.
> > >
> > > I hope you find this as interesting as I did.
> > >
> > > Cheers!
> > > -Pete
> > >
> > > --
> > > Pete Stephenson
> > > _______________________________________________
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