To make a parallel DAC that's monotonic and doesn't have oversize steps at the major bit carries, you need switches that introduce very small voltage errors (less than 1/2 LSB worth of voltage at the MSB carry) or else errors that are reproducible within 1/2 LSB from bit to bit. Generic output pins from logic chips don't do that. I've done some designs of fast parallel DACs with R/2R ladders and variant architectures, and getting the right switches and a stable reference rail is the biggest challenge. Doing it at a high update rate just makes everything tougher, and building it out of separate switch chips and resistor arrays just makes everything harder, because the physical size of the PCB interconnects between components adds stray inductances and capacitances. If you can buy the DACs and line drivers, it's a lot easier.
Jack Carroll ----- Original Message ----- From: "Timothy Normand Miller" <[email protected]> To: "Ing. Daniel Rozsnyó" <[email protected]> Cc: [email protected] Sent: Wednesday, October 31, 2012 9:48:35 AM Subject: Re: [Open-graphics] The next OGA card? Actually, if we have lots of I/Os to spare, we might be able to do analog video using a resistor network and a low-pass filter. Someone with a better EE background could answer that. _______________________________________________ Open-graphics mailing list [email protected] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
