🚀 go-pugleaf

In article <7973@microsoft.UUCP> brianw@microsoft.UUCP (Brian Willoughby) writes:
>In article <1845@draken.nada.kth.se> d88-jwa@nada.kth.se (Jon W{tte) writes:
>
>>>>transitions take longer than 1 to 0 transistions.  Then, for a digital
>>>>sample changing from $8000 to $7FFF, you would first get $0000 on the
>>>>DAC output before all the other 15 bits changed to $7FFF.  Ugly and BIG
>>>>spike!  Analog sample and hold allows the outputs to be disconnented

How about Gray Code?  Apart from the p = 0.999 chance that no manufacturers
currently make Gray code DACs, the advantage to this method would be less
of a spike due to large numbers of bits changing simultaneously.  In Gray
code, only one bit changes between each successive ADU (Analog to Digital
Unit) increment.  OK, so that would fix the problem of large spikes on the 
analog ground (ahh, a separate regulated power source for the analog half 
of the DAC?  That would go a long way towards reducing metallically 
coupled digital switching spikes to the analog output.  The EMI switching
spikes may have to be contended with by MMIC (Monolithic Microwave
Integrated Circuit) device design philosophies on-chip.

Again, OK, Gray code would counteract switching noise for increments of 
1 in the signal, but what about increments (or decrements) not = 1.
Is there a more advanced Gray code that will minimize the number of 
bits changing ~simultaneosly within a certain range?  For instance, a 
second order Gray code that would minimize the number of bits that
could change for an increment +/- 1 and +/- 2. Etcetera for third
order....  

Is there a better way, or does it all come down to parallel antennas
radiating garbage to our delicate wires?

Greg Harrison
My opinions are not intended to express those of GE.