ULTRA-miniature crystal inside AVRISP mkII!

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So I cracked open my AVRISP mkII and noticed that there is an incredibly small crystal on the ATMega128 inside that is approximately 3mm x 1.0mm (long and skinny) with no additional load capacitance. It looks like the letters "AJ" are written on it, but otherwise there are no distinguishing markings.

Does anybody happen to know what this crystal model / manufacturer is? I would love to start using it in designs. :D Thanks!

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If there's no external load, it's likely a ceramic resonator.

Jörg Wunsch

Please don't send me PMs, use email if you want to approach me personally.

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Possibly, or the intrinsic capacitance of the XTAL inputs on the AVR are sufficient for this small crystal. They're on the order of 10-12 pF IIRC.

See the attached picture of the metal can.

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That is for sure a ceramic resonator.
They are made by Murata for example.
The precision is not as good as that of a Crystal.

Marcus

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The JTAG ICE mkII also uses such part for one of the ATmega128s.
The other one appears to be clocked from a 14.7 MHz crystal (or
crystal oscillator), certainly due to it being responsible for
driving a RS-232 line as well.

The resonator on my JTAG ICE is marked "At", the one on my
AVRISP mkII is marked "Ar".

Jörg Wunsch

Please don't send me PMs, use email if you want to approach me personally.

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Hmm that is too bad. I saw the metal can and assumed crystal.

Thanks for the info!

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Murata CSTCR-G series. 0.5% initial accuracy, 0.2% over temperature, which is plenty good enough for the vast majority of microcontroller applications.
http://www.farnell.com/datasheet...

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I don't own an AVRISP-2. I am rather surprised that the whole thing does not consist of a single 32kB USB AVR with a single level-shifter chip.

I would also expect a 'good' 12MHz for the USB. USB is probably more critical for timing than RS232.

What do they do with 128kB of flash memory?

David.

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David it's an August thread but 7 years old :wink: Maybe you know already....

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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No. I had not noticed the date !

Had someone replied today, and subsequently deleted their post?

My comment still applies: "what do they put in 128kB flash ?"

David.

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Quote:
Had someone replied today, and subsequently deleted their post?

Ordinary mortals can not delete a post of theirs unless it is at the tail of the thread.

I think I reported recent SPAM in this thread today or yesterday, and the mods (with extraordinary powers) has removed the spam post.

Could very well have been King Samperi that did the removing, in which case you are on an equal level of confusion.

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Quote:
My comment still applies: "what do they put in 128kB flash ?"

Let me think, the device services only synchronous protocols (ISP + PDI + TPI) so it does not rely on response time as it is a master then, no explicit speed limits (apart from this required user experience)..
AFAIK Dean has squeezed all that ISPMk2 together with USB stack into AT90USB162.
I bet the original one holds some AES algorithm with smarter 32kB programming limit :twisted:

No RSTDISBL, no fun!

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Yes. I am sure that it has an encrypted bootloader. That is why I suggested a 32kB chip might be necessary rather than Dean's USB162.

Looking at the photo, there only seem to be about 30 pins used from the QFN-64 package. So package size seems overkill too.

Oh, the JTAG programming commands are described in the data sheet. There is no need to visit hacking sites.

David.

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Quote:
Could very well have been King Samperi that did the removing
Not me.

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I saw this thread this morning and prepared a photo of a cute crystal I've been using lately. But then I saw it was a centuries old thread, so I didn't post.

Well, since it's on the topic of small crystals, here goes.

It's a TX325-16F18X-AC3 between 2 22 pf caps.

Attachment(s): 

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This one is really tiny (1.6 x 1.2mm).

No RSTDISBL, no fun!

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Not quite up to buying 3000 at a time yet :wink:

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

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Well, then get this one:
http://www.digikey.com/product-d...

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Wow. 1.6 x 1.2 x 0.4mm $1.89 for 1
Mine is 2.5 x 3.2 x 0.6mm $0.60 for 1

Pretty nice part.

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

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Why do all those SMD crystals have 4 terminals? Is it for some drop-in quartz generator compatibility?

No RSTDISBL, no fun!

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Quote:

Why do all those SMD crystals have 4 terminals? Is it for some drop-in quartz generator compatibility?


The datasheet pinout/block diagram indicates the other two pins are Gnd. To help with noise?

Note that the 8Q crystal line being linked to is 24MHz-54MHz. That would correspond to the rule-of-thumb "the lower the frequency the bigger the crystal needs to be", right?

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.