>> I noticed that on p. 3, the ST part (U300) has PVDD and PVSS >> connections through 4.7 ohm resistors to PWR and GND, respectively. I >> can see using a small resistor + shunt cap to GND in series with the >> power connection to attenuate power supply noise. However, why is the >> PVSS connection to GND also going through a resistor? > > There's noise on both power and ground lines. The P* pins are for the > PLL's power supply, which need as clean a power source as you can > provide.
Did you use a ground plane? If so, then I'd expect that the plane is quiet, and it would be better to connect directly. Or am I wrong? Of course, if you used tracks for ground on the same plane as other signals, then you're right. Putting a cap between PVDD and PVSS, and a resistor to PWR and GND makes sense. But anyway, thanks for the answer. It makes sense. Stuart _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user