[Coco] new high density controller

[jdaggett at gate.net]

On 10 Aug 2006 at 9:22, Mike Pepe wrote:

> jdaggett at gate.net wrote:
> 
> > *****************
> > 
> > The integrator ( filter) circuit on the PUMP pin, which by the way is an output, is there to 
> > filter the error pulses generated by the phase detector of the VCO system. You need to only 
> > have one value for this filter. The widest step in frequency would determine the cutoff 
> > frequency of the integrator. In the case of SD to HD would be  the frequency difference 
> > between 125Kb/Sec to 500Kb/Sec data stream.
> > 
> > 
> > james
> > 
> 
> Hi James,
> 
> I trust your judgment, though the data sheet for the chip does specify 
> two values. I was working on using a relay to switch them. (ugh)
> 
> I may just have to try it and see if I can get the 2793 to work.
> 
> -Mike
**************

In an ideal world it would be best to have both. While it is not necessary. 
Setting the values for the higher data rate will cause the filer to be 
underdamped when switching to a lower data rate. This will cause excessive 
ringing in error signal and will increase lock time,  stable VCO operation, for 
the VCO. 

While technically this will be a problem the data rate is slow enough that 
some amount of overdamped condition is tolerable when switching from 
high speed to low speed data rates. 

james