Hi,
Updated as below:
http://en.qi-hardware.com/wiki/Protection_of_Reversed_Polarity_on_DC_plug-in#Sch._D-1
When input attempted below:
1) +7V, +7.5V, +9V, +12V, + 20V:
Zener voltage varies from roughly 5.6V into 2.865V ~ 2.206V individually
in couple seconds. Voltage of symbol "5V" marked on M1 RC2 descends
individually to 2.557V ~ 2.164V. Unbooted.
2) +6.5V:
booted, with most high temperature (50.5 / 61.3°C) among all attempts.
3) 6V:
booted, with (44.3 / 57.5°C)
4) +4.75V, +5V, +5.25V:
booted, with (35.3 ~ 39.6°C) , Voltage of symbol "5V" marked on M1 RC2 =
4.413 ~ 4.891V; Although 4.413 V is a bit lower than 4.75V, my Fujitsu
mouser MP117-P & Logitech M-UAS144, keyboard Genius GK-090017 works well.
5) -4.75V, -5V, -5.25V, -6V, -6.5V, -7V, -7.5V, -9V, -12V, -20V:
current diverts return to input source, expected functionality( against
reversed polarity ) works.
Since the DC adapter 5V +/- 5% comes with board, eventually with Zener and
resettable fuse, got some over-voltages/reversed polarity protection goals
without regression.
-adam
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