[time-nuts] fluke.l monitor for Thunderbolt . . . the sagacontinues

[David VanHorn]

Vf is highly dependent on current and temperature.  The processor alone is a very dynamic load. 
I wouldn't trust it in a hobby project, and I can't imagine proposing it for a professional design.

Without knowing much in details, a bog standard 3.3V regulator is $0.78 at Digikley, in singles.
L78L33ABZ-AP
If there are unusual requirements, then that might go up.



________________________________________
From: time-nuts-bounces at febo.com [time-nuts-bounces at febo.com] On Behalf Of shalimr9 at gmail.com [shalimr9 at gmail.com]
Sent: Wednesday, July 06, 2011 5:34 PM
To: Time-Nuts
Subject: Re: [time-nuts] fluke.l monitor for Thunderbolt . . . the      sagacontinues

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.VanHorn at elec-solutions.com>
Sender: time-nuts-bounces at febo.com
Date: Wed, 6 Jul 2011 14:56:47
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
        <time-nuts at 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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