At this point I feel I should fall back on "magic" as an answer...
I have, occasionally and accidentally, powered MOS circuits
through input lines. Maybe there's enough leakage.
MS
xi zhang wrote:
Hi,
Thanks for the reply. However, when I remove the D22 diode, the LEDs
still blink when powered through USB. Why is that so?
Best Regards,
Xi
2007/9/27, Michael Schippling <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>>:
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
>
>
>
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