Re: gEDA-user: Question for DJ about his alarm clock

[Stuart Brorson <sdb@xxxxxxxxxx>]

>> 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@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user