On Fri, 2011-05-06 at 21:51 +0800, Adam Wang wrote: > 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
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. The problem is not present on RC1. So, as far as the ferrite beads go, we either: 1) check carefully their incoming quality 2) remove them entirely from the 5V input (it's not clear that they are really needed) If you can confirm that the voltage drop only comes from the beads, the only remaining unknown about the protection circuit is your claim that the zener heats, even though no current is supposed to flow through it. S. _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkymist@Freenode Twitter: www.twitter.com/milkymistvj Ideas? http://milkymist.uservoice.com
