Because a real regulator costs more than 3 diodes and when you already have a
5V regulator, the 3 diodes work fine.
Didier
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: David VanHorn <d.vanh...@elec-solutions.com>
Sender: time-nuts-boun...@febo.com
Date: Wed, 6 Jul 2011 14:56:47
To: Discussion of precise time and frequency measurement<time-nuts@febo.com>
Reply-To: Discussion of precise time and frequency measurement
<time-nuts@febo.com>
Subject: Re: [time-nuts] fluke.l monitor for Thunderbolt . . . the saga
continues
I've heard this discussed a few times, and the idea of using diodes to
"regulate" this way makes me very queasy.
Why would a real 3.3V regulator not be used?
________________________________________
If the new chip requires 3.3 vdc and there aren't 3 diodes on the board to drop
the 5 vdc down, this will be a problem. The old board had 3 zero ohm resistors
in place of the diodes and this is why some of the boards failed. As I had
posted previously, I used a red LED as a 1.7-1.8 volt zener to drop the 5 volts
down to the proper value. The LED went in place of the 3 regular diodes.
-Arthur
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