Powering up puzzle
#13
(2017-06-14, 23:12)kevinmcc Wrote: I still think they should add a protection diode to the 3.3 V rail.

Can't use a series diode, it would drop to much voltage in forward mode.

Parrallel zener? Maybe but it has to have a high enough voltage such that an "enthusiastic" nominal 3.3 V supply doesn't cause it to conduct but low enough that it'll conduct before the nominal 3.3 V components get fried. The +5 V regulator is a nominal 250 mA device but has a typical short circuit current of 500 mA, so this 3.5 V has to dissipate 1.75 W or more...

Best not to fiddle with the power jumpers with the unit powered up.  B-)
Cheers
Dave.

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Messages In This Thread
Powering up puzzle - by MonkeeRench - 2017-06-12, 21:15
RE: Powering up puzzle - by kevinmcc - 2017-06-12, 23:03
RE: Powering up puzzle - by MonkeeRench - 2017-06-13, 15:51
RE: Powering up puzzle - by kevinmcc - 2017-06-14, 00:13
RE: Powering up puzzle - by MonkeeRench - 2017-06-14, 02:15
RE: Powering up puzzle - by kevinmcc - 2017-06-14, 05:03
RE: Powering up puzzle - by DelandeC - 2017-06-14, 08:42
RE: Powering up puzzle - by allsorts - 2017-06-14, 10:03
RE: Powering up puzzle - by kevinmcc - 2017-06-14, 23:12
RE: Powering up puzzle - by BobW - 2017-06-15, 04:11
RE: Powering up puzzle - by cutty - 2017-06-15, 05:38
RE: Powering up puzzle - by allsorts - 2017-06-15, 16:20
RE: Powering up puzzle - by kevinmcc - 2017-06-16, 22:57
RE: Powering up puzzle - by BobW - 2017-06-15, 12:05
RE: Powering up puzzle - by allsorts - 2017-06-15, 18:18
RE: Powering up puzzle - by Jon Point - 2017-06-16, 01:11
RE: Powering up puzzle - by allsorts - 2017-06-17, 22:39

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