[time-nuts] Anybody want a Thunderbolt power supply

Dave Brown tractorb at ihug.co.nz
Thu Sep 1 00:09:45 EDT 2016

Getting the required Thunderbolt supply rails from a nominal 12v dc supply 
of doubtful cleanliness is an issue that also needs to be addressed.  I'm 
still mulling over that one. (and using a triple output switcher from an 
inverter backed mains supply meantime!)
 The ex-telco GPSDOs all run on a nominal 24-50 volt DC supply but I don't 
know how they generate their internal supplies. I suspect switchers?
DaveB, NZ

----- Original Message ----- 
From: "Charles Steinmetz" <csteinmetz at yandex.com>
To: <time-nuts at febo.com>
Sent: Thursday, September 01, 2016 3:35 PM
Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply

> Bruce wrote:
>> Low noise regulators for the +12V and +5V outputs would also be useful.
> Very true.  By focusing on the -12v supply, I did not intend to suggest 
> that low noise is unimportant on the +12v and +5v supplies.
> The suggestion to use LT3042s is a good one, but note that it has an 
> output current rating of 200mA.  The Tbolt needs ~250mA at +5v, and ~700mA 
> at +12v [at startup -- but only ~150mA steady-state, depending on ambient 
> temperature].  LT3042s can be used in parallel, so two of them for the +5v 
> supply and four of them for the +12v supply would be required.  That isn't 
> so bad for the +5v supply, but seems excessive for the +12v supply 
> (particularly when three of the four are needed only during warmup from 
> cold).
> The LT3088 and LT3080 will deliver 800mA and 1.1A, respectively, with low 
> noise (but not as low as the LT3042).  One of those might be a better 
> choice for the +12v supply.  Similarly, the LT3085 can deliver 500mA, so 
> one of those could be used for the +5v supply.
> Finally: Linear Technology -- Where is our negative-voltage complement to 
> the LT3042?
> Best regards,
> Charles
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