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

Gerhard Hoffmann dk4xp at arcor.de
Sun May 8 18:45:37 EDT 2016


Am 08.05.2016 um 21:53 schrieb Attila Kinali:
> 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.
>
You can run the ADC on constant 100 MHz for example. The charged 
capacitor has to wait an
extra  0 to 10 ns until it is read out. That is easy. In a time 
stretcher you must keep the charge and
discharge it in a controlled way in 50 usec, and over that time, bias 
currents etc really
do play a role.

regards, Gerhard




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