[time-nuts] High rate, high precision/accuracy time interval counter methods

David davidwhess at gmail.com
Sun May 8 21:45:34 EDT 2016


On Sun, 8 May 2016 21:53:56 +0200, you wrote:

>On Wed, 4 May 2016 15:26:37 +0200
>Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
>
>> Indeed. ADC conversion speed is not a big issue these days, so the Nutt 
>> style of interpolator is just expensive to parallelize for speed, the 
>> time-to-voltage system is better and should have a much better 
>> recycle-time and thus result in less hardware needs.
>
>True and not true. Yes, there are many ADCs that do high conversion
>rates, but these are optimized for piplined applications where conversion
>happens at a constant rate. Ie they expect a constant conversion clock
>with a constant rate. If you want to trigger conversion at an arbitrary time,
>you either have to build your own sampler or need to  use one of the
>non-pipelined ADCs whic are much slower (IIRC they stop around 5-10Msps
>aka >100ns conversion time). Flash ADCs with direct access to the sampling
>circuitry are basically extinct.
>
>			Attila Kinali

An integrating time to voltage converter effectively is an external
sample and hold so pipelined analog to digital converters are not a
problem except in complexity dealing with their latency.

Huh, Flash ADCs really are almost gone now and I did not even notice.
TI still has some available.

I wonder what the fastest SAR ADCs are now.  Linear Technology is up
to 18 bits and 15 Msps in the same device but if it was the only
option, then its cost would convince me to consider alternative
designs.


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