Michael is correct here: the power from the USB connector U4 (about 5V) goes through a U25 which is a voltage regulator that produces 3.3V. That voltage goes through the diode so that the USB side of the mote is not reverse-powered when the mote runs on batteries and the mote is disconnected from USB.
Cheers, Rob On 9/27/07, Michael Schippling <[EMAIL PROTECTED]> wrote: > Boy, that's a tough one...I'm not entirely sure without looking up all > the chips but I think when powered by the USB it goes sorta like this: > > page 3 top-left "USB Interface" > U22 pin 4 -- power from host -- becomes U_VCC > U25 TC55RP33 -- does some magic to make -- P_DVCC > > page 3 top-right "Mote Power" > P_DVCC -- goes through D22 to become -- VCCin > (I'm not clear on the use of a Zener here, if that is what it is...) > > page 1 top-right "Power" > VCCin -- goes through L2 to become -- DVCC > > But, if as you say, ( PWR_CONN) U4 pin 1 - VCCin - does not connect > to D22 pin2 - VCCin - then all bets are off. Make sure you got the > right pin of the diode when doing the continuity check, or the > right polarity if checking through the diode... > > MS > > xi zhang wrote: > > Hi all, > > I'm trying to profile the power consumption of the TelosB mote when > > powered from USB. I've looked at the schematics of TelosB but I could > > not figure out how the DVcc is generated when powered through the USB. > > In addition, I would also like to know where is the Vccin (which is fed > > to diode D22) generated since a short circuit test has shown that it is > > not from power supply U4. > > > > Thank you very much! > > > > Best Regarts, > > Xi Zhang > > > > > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Tinyos-help mailing list > > Tinyos-help@Millennium.Berkeley.EDU > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > _______________________________________________ > Tinyos-help mailing list > Tinyos-help@Millennium.Berkeley.EDU > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > _______________________________________________ Tinyos-help mailing list Tinyos-help@Millennium.Berkeley.EDU https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help
