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" <[email protected]>
To: <[email protected]>
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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