Adam Wang wrote: > In fact that USB switch does protect 5V(J21/J3) rail at the > beginning,
I'm not sure the switch is doing much at the beginning. Some of the effects we see are contact bounces from the relay (I used labsw to avoid mechanical stress on the USB receptacles) and then also the capacitors we have in place all around the USB power switch. > When usb switch reached short-current condition, the F2 must also try to > trip firstly then recover its positive resistance and arise back normally > up 4.6V within 40 ~ 50 us. This reality is decided now by PTC fuse-oriented. Hmm, I'd be worried about dropping even more voltage on any more components connected in series. > One thing, the "Input" noticed that from your lab supply should be > regarding as a real output voltage of the official adapter with > 2.5m cable: Yes, definitely. My lab power supply doesn't know how much is dropped on the connectors and - relatively long, 2 m - cables. > So maybe you can tune highly a bit on the lab supply's voltage as the > "Input" column for real application. That's why i varied the source :) The rows with a nominal voltage of 5.10 V and 5.20 V should correspond to an input of 5.0 V. Unfortunately, the behaviour at these points isn't any better than with a real input of 4.86 V. - Werner _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkymist@Freenode
