AVR-Chat

On Sat, Nov 21, 2009 at 11:54 PM, Philippe Habib <phabib@well.com> wrote:

>
>
> I'm taking an FPGA class right now and as a project, I'm working on an
> application that's now done with discrete logic. The logic needs to
> measure pulses with 10ns resolution. You can't do that with a micro
>
It can be done in the analog domain a lot easier.  Not all solutions
are best solved in the digital domain, for example see Figure #25:

http://www.linear-tech
.co.jp/pc/downloadDocument.do?navId=H0,C1,C1155,C1001,C1158,P1442,D1594

That circuit has a few problems, it is also based on ten+ year old parts.

Make a current source out of a current feed back op-amp that
has a high slew rate for charging the cap, feeding a fast track&hold.
The A/D itself does not have to be all that fast, as long as there
is little drupe before the sampling cap starts to discharge.

Also check out:

"High-Speed Time-Domain Measurements�Practical Tips for Improvement"

http://www.analog.com/library/analogDialogue/archives/41-03/time_domain.html


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