[time-nuts] Experience with THS788 from TI?

Magnus Danielson magnus at rubidium.dyndns.org
Fri Mar 23 08:37:58 UTC 2012


On 03/22/2012 10:17 PM, Attila Kinali wrote:
> On Thu, 22 Mar 2012 11:12:40 -0400
> Ben Gamari<bgamari at physics.umass.edu>  wrote:
>
>>> If you are really going to build your own design, then i suggest you
>>> read these papers:
>>
>> Thank you very much for this list. While I have already stumbled upon a
>> few of the FPGA papers, I'm largely ignorant of the other possible
>> approaches. Given the limitations of FPGA TDCs, it will be nice to see
>> what is possible by other means.
>
> I'm quite sure there is much more around. I only dug a little bit a
> weekend or so and got a couple of intersting papers. It is also a
> good idea, to dig trough old circuit descriptions, form the 70s and older.
> You will find there many forgotten gems, that get increasingly relevant
> when you leave the digital domain, especially when going high speed.
>
>> That being said, I'm quite keen on bringing up something on the FPGA. I
>> just got the power supplies on the PandaDAQ running last night (QFN is a
>> pain without my shiny new hot air rework station), so it seems that soon
>> enough I'll have a Spartan 6 at my disposal.
>
> *g*
> If you do QFN or any serious SMD stuff, get a Leiter HOT JET S
> with fine nozzles (3mm and 5mm), or anything similar. Normal hot
> air guns don't really work and a complete rework station is way
> too expensive for anything a mere mortal does. On the other hand,
> with such a Hot Jet S (or similar) you can even solder BGAs, reliably.
>
>
>>> "Time-Interval Measurements Based on SAW Filter Excitation", by Petr Panek, 2007
>>> "Time interval measurement device based on surface acoustic wave filter
>>> excitation, providing 1ps precision and stability", by Panek and Prochazka, 2007
>>> "Random Erros in Time Interval Measurement Based on SAW Filter Excitation",
>>> by Petr Panek, 2008
>>> A very nice idea on how to use a high frequency startable oscillator with
>>> an ADC as phase detector. Panek claims to get below 1ps with a 200MHz clock
>>> and a 525MHz filter/oscillator. His calculations indicate that the ultimate
>>> limit of resolution is given by the sampling jitter of the ADC and the
>>> frequency and bandwidth (ie the Q of the oscillator). There
>
> Oops.. "There" is a sentence missing... Interrupts are bad for emails.
>
> There is even a report of a similar design, using an LC tank as resonant
> circuit that got into the<10ps RMS region. See "High frequency, high time
> time resolution time-to-digital converter emplying passive resonant circuits",
> by Ripamonti, Abba and Geracy, 2010
> http://risorse.dei.polimi.it/digital/products/2010/High%20frequency,%20high%20time%20resolution%20time-to-digital%20converter%20employing%20passive%20resonating%20circuits.pdf
>
>>> But getting to below that will not be
>>> easy. Mainly due to all those side effect, non-idealities and other
>>> stuff you have to deal with. And be aware, that you are dealing with
>>> an high frequncy/high speed circuit. Crudly said, you are in the
>>> ballpark of a 1/10ps = 100GHz system. Everything has to be right to
>>> get you there.
>>
>> Sure. This is the real issue. I am a physicist by training, so the
>> basics of high-speed design are largely a mystery to me. From
>> application notes (in particular Jim Williams' old but very readable
>> work) I've gleaned the following,
>>
>> 1) Keep traces short and well impedence matched
>> 2) Ample bypassing
>> 3) Ground plane is essential
>
> 4) Know where thy return path is!
>
> I recommend getting the Tietze-Schenk "Halbleiter Schaltungstechnik"
> (resp "Electronic Circuits" in englisch). It's like Horowitz, just
> with more theoretical background and more explenation how to design
> stuff. Ie you get the formulas to calculate what you need if you want
> to go to the limit. It's still very much practical (only as much
> theory as needed) but covers enough of the theory if you want to have
> more than just cookbook examples.
>
> I'm still looking for a good high speed / high frequency book.
> I've asked for literature in that area a few weeks ago on this
> list, but have not gotten the time yet to read all those books.
> You might want to check the answers too.

For high speed digital design this is a good starter:
http://www.amazon.com/High-Speed-Digital-Design-Handbook/dp/0133957241/ref=sr_1_1?ie=UTF8&qid=1332491581&sr=8-1

It's a very good read and accelerated my knowledge quickly in one blow 
many years ago. It's not heavy on the math department, but teaches what 
the effects are and gives lot of thumb-rules which is easy to remember.

It was then followed by:
http://www.amazon.com/High-Speed-Signal-Propagation-Advanced/dp/013084408X/ref=pd_bxgy_b_text_b

Which goes deeper.

While the focus is digital designs, much of the physics is the same for 
RF. Few of the RF books I've seen has come close to the practically 
oriented teaching of these books.

Cheers,
Magnus



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