[time-nuts] Modeling vs reality question re my TIC

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Mar 10 18:32:22 EDT 2014


Charge injection could well account for the offset from the expected 
minimum.
There are no forward biased diodes in your circuit.

It would be helpful to capture the 125 buffer input signal waveforms 
(and if possible the timing capacitor waveform) rather than trying to 
infer whats going on from the ADC plots.


Bruce

Bob Stewart wrote:
> Wouldn't those types of problems tend to make the result worse in some obvious way, instead of better than expected?  I'm getting an ADC swing from about .7V to about 2.4V; which corresponds to the usual diode sink at .7V and probably just blind luck with the 2.4V max being so close to the 2.5V VRef.
>
>
> In the plot below, I zapped the DAC on my system to get a picture of the charge ramp.  The red dots are the TIC with the 10ns uncorrected jitter from a nav receiver.  The purple is a 30 second rolling average.  Am I right in thinking this is a typical RC charge ramp?  Not trying to be argumentative, I'm just trying hard to understand.
>
>
> http://www.evoria.net/AE6RV/TIC/ChargeRamp.png
>
>
> Bob
>
>
>
>
>    
>> ________________________________
>> From: Bruce Griffiths<bruce.griffiths at xtra.co.nz>
>> To: Bob Stewart<bob at evoria.net>; Discussion of precise time and frequency measurement<time-nuts at febo.com>
>> Sent: Monday, March 10, 2014 3:53 PM
>> Subject: Re: [time-nuts] Modeling vs reality question re my TIC
>>
>>
>> Metastability in the Flipflops?
>>
>> Charge injection when tristating tristate buffers?
>>
>> Neither of which are included in your models.
>>
>> Bruce
>>
>>
>>      
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