[time-nuts] Gate propagation delay jitter

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Apr 10 20:09:25 EDT 2007


SAIDJACK at aol.com wrote:
>  
> In a message dated 4/10/2007 14:28:11 Pacific Daylight Time,  
> bruce.griffiths at xtra.co.nz writes:
>
> Then we  would need to know/measure the jitter of the retiming flipflop.
> There  appears to be little definitive published data on the jitter of 
> various  logic gates and flipflops.
> Consequently a simple reliable method of  measuring such jitter would be 
> useful.
>
>
>
> Hi Bruce,
>  
> if I remember correctly, Philips makes a special low-metastability 74 FF  
> chip. It has guaranteed metastability-recovery time, and seems to be the only 74  
> type chip out there with that claim to fame.
>  
> They really looked at the timing of that part, maybe there are some jitter  
> specs available, if not in the datasheet then potentially through your  local 
> NXP rep :)
>  
> bye,
> Said
>
>
>
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>   
Said

Yes, I remember coming across that device.
It is easier to obtain data on the metastability characteristics of gate 
arrays and SSI flipflops than it is to find reliable data on propagation 
delay jitter.
TI provide info for 74AC and 74HC devices, but make no guarantees, I 
guess its a matter of the cost of testing.
Testing/measuring the metastability characteristics of a flipflop isn't 
too difficult albeit time consuming.

Bruce




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