[time-nuts] Thunderbolt

TheInfamousFlavio at hotmail.com TheInfamousFlavio at hotmail.com
Sun Mar 4 22:25:08 EST 2007


You're right about the ripple but you have consider stability.  The spec 
that you pointed out,  states that 5V connectors are load-share.  That 
implies that there is some circuitry or ic's that control current sharing 
between that those two connectors which, in turn, implies that the 5V 
circuitry on the receiver board is sensitive to current shifts or load 
changes.  Now you could hook up a couple of  lab power supplies and that 
would probably do the trick, but your talking about power supplies that are 
way overkill what's needed and not practical.  There is a lot more than just 
a DC-DC converter on the power supply board of a standard thunderbolt and I 
still contend it's there for a reason.  Mid range power supplies and cheap 
switchers may be able to handle the ripple, but switchers are notorious for 
poor handling of load and it's not really clear how a mid range power supply 
is going to handle load demands on such potentially sensitive circuit.
Even if we were to design a reasonable ps setup for the 1/2tbolt for a 
particular set of conditions, there still would have to be a considerable 
amount testing that would have to be done to make certain the setup would 
work in "real-world" environment.  Too many unknowns.

-Flavio





----- Original Message ----- 
From: "Colin Bradley" <colinbradley10 at yahoo.com>
To: <time-nuts at febo.com>
Sent: Sunday, March 04, 2007 00:17
Subject: [time-nuts] Thunderbolt


> The power supply for the Thunderbolt should not be a showstopper.  The 
> manual spec states that
> the board needs +12vdc @ 750ma max and -12vdc @ 10ma with ripple at 75mV 
> P-P. The rest of the board needs +5vdc @ 400ma with ripple a spec of 50mV 
> P-P, which is a mid quality power supply. Lab supplies are usually < 5mV 
> P-P, with cheap switchers above 100mV P-P. The reason that most telco 
> units have DC converters is the use of 48vdc power common in that 
> industry.
> Colin
>
>
>
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