[Discuss-gnuradio] USRP RF Daughterboards

[David Bengtson]

Hi Matt:

Quick question on powering rf daughter boards. Looking at the schematic 
for the USRP, it looks like the external power connector goes to U502, 
which is a 3.3 V Regulator. DVDD comes right off the output of U502, and 
then AVDD is derived from DVDD by the filter's around L511, L510, L600, 
L601. It seems that there are two separate analog rails, AVDD1 and 
AVDD2, which power different thing's  on the USRP. How quiet are these 
lines?
I'm right now leaning towards hanging a 3.3V regulator off the +5Vdc 
supply to power the GPS daughter board I'm working on.
Also, where does the reference voltage for the ADC's come from?

Thanks


Dave