One concern I have is that with a 5.6V zener (1n5339), limiting the 5V rail to 5.6V volts if there is an overvoltage on the power input. I see that the 5V rail is connected directly to USB VBUS which is specified in [1] with a range of 4.45 to 5.25V (Section 11.4.5 Table 11.2). The 74LVC logic has an absolute max of 6.5V, I'm not sure about EDID/DDC on the DE-15 RGB connector. There is no inrush limiting or current limiting on the USB ports except via the PTC. The Nat Semi (now TI!) Simple Switchers are very easy to use and design for. I've designed boards using the LM2675 in a buck configuration based on the datasheet and have never had a problem. The datasheet spec standard magnetics/inductors available from Digikey.
Cheers, Ed. [1] http://www.usb.org/developers/docs/usb_30_spec_092911.zip > Date: Sat, 29 Oct 2011 08:06:24 -0300 > From: [email protected] > To: [email protected] > Subject: Re: [Milkymist-devel] The dungeons of NORia: Meeting the Balrog > > S?bastien Bourdeauducq wrote: > > I tried connecting the 12V supply to my M1. The polyswitch/zener > > protection tripped and nothing bad happened in the long term. > > :) > > Yeah, you probably noticed that I'm bitching a lot less since the > addition of the protection circuit in M1rc3 ;-) > > But I'm thinking more of the ability to operate properly even if > the supply is bad. E.g., maybe you could also get away with a 6 V > supply ? Or maybe only sometimes ? Then there are supplies > without proper regulation where "5 V" is in reality all over the > place, depending on load and barely recognizable as DC. > > My horror scenario is a traveling VJ who arrives at the club > already in a hurry, then realizes the power supply is still at > the hotel. Then someone at the club finds a supply that, at a > quick glance, looks right ... > > - Werner > _______________________________________________ > http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org > IRC: #milkymist@Freenode
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