[Milkymist-devel] [MM1] experiments about resettable fuse and zener diode on rc2

[Adam Wang]

> Much of this unexpected voltage drop probably comes from the 1206
> ferrite beads at the input. Another thing we learn...
> Please measure the voltage across them (probes on the bead's pads) to
> make sure. I easily get 100mV to 200mV drop on RC2 (depending on load)
> across the beads, even though the datasheet
> http://www.yuden.co.jp/ut/product/inductor/FBMJ3216HM600-T.html
> says that their resistance is 0.01 ohm maximum. But it seems that we
> rather have 0.1 ohm here.
>

Yes, you are right that I confirmed RC2 have used faulty 1206 beads.
After replaced L10/L11, their drops are only 3mV.

The all previous results were wrong caused by my mistake made on ignorance
of extended cable loss and faulty beads. After fine calibration, redo; see
correct results:

http://en.qi-hardware.com/wiki/Protection_of_Reversed_Polarity_on_DC_plug-in#Sch._D

Voltage of symbol 5V marked on M1 RC2:

5.199 V @ 5.25V input,
4.951V @ 5.00V input,
4.699V @ 4.75V input,

VL10 is about 3.5mV, VL11 is about 3.3mV, Vfuse is about 38mV.
e.g. :
0.0035 + 0.0033 + 0.0378 + 4.699 = 4.7436, closed to 4.75 input.

With regards to discussions about if remove parts, check logs on
http://en.qi-hardware.com/mmlogs/milkymist_2011-05-09.log.html
-adam
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