Hi
The control voltage on the 12 V OCXO is likely 0-10V or 0-5V. The tune on the
3.3V part isn’t going to be above 3.3V and it may be 0-2.5V. The 3.3V part is
going to be at least 8X more sensitive to grounding issues.
To put this in perspective, you can see a change on a normal 12V part
On 10/31/13 4:02 AM, Bob Camp wrote:
Hi
The control voltage on the 12 V OCXO is likely 0-10V or 0-5V. The
tune on the 3.3V part isn’t going to be above 3.3V and it may be
0-2.5V. The 3.3V part is going to be at least 8X more sensitive to
grounding issues.
I've got a BUNCH of VCOs that are
: Wednesday, October 30, 2013 10:54 PM
Subject: Re: [time-nuts] Surface Mount OCXO Questions
Graham,
Good points - yes, I have this part currently in the design: TPS75833KTTT
(LDO from TI) - putting another one down
(just) for the OCXO isn't a problem.
And a nice 12V rail isn't a problem either
, etc.)
Bob LaJeunesse
From: John C. Westmoreland, P.E. j...@westmorelandengineering.com
To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Sent: Wednesday, October 30, 2013 10:54 PM
Subject: Re: [time-nuts] Surface Mount OCXO
Hi
There are a *lot* of SMT OCXO’s out there. A J lead part is SMT, but identical
to it’s through hole counterpart. It will mount pretty much same / same….
Bob
On Oct 29, 2013, at 10:18 PM, John C. Westmoreland, P.E.
j...@westmorelandengineering.com wrote:
Hello,
I was wondering if I
John:
All SMT OCXO's will either have a recommended PCB footprint in the spec
sheet
or will refer you to a recommended footprint in another document.
Some don't care about a ground plane under the part, some require it
with no crossing signals, some require an open thermal hole underneath
the
Graham and Time Nuts,
(thanks for the answers.)
I have another question - I am looking at a part from MTI. I wanted to use
one of their 3.3V parts. They are telling me to use the 12V part because
the 3.3V part can have an issue with ground loops due to the higher current
requirements at that
Hi
Consider that microvolts matter on the EFC. Unless you have a separate return
for the oven current it’s going to be tough to keep everything separate. One
might ask “why no separate return”. Well when you design one in, and then go
look at people’s layouts - you might as well not have
Bob,
OK - that makes sense. If you follow good analog/digital layout rules then
this may not be a problem. But your point about the EFC sensitivity is
well taken.
But, that is always a problem.
Yes, do a lot of people violate good analog/digital layout rules,
especially on the ground planes -
Hi
You may have a good layout on your board, but they have to get the current to
that pin / pad somehow. In all likelihood the amps of current through the pad
it’s self are going to cause issues. Also remember that the ground is likely an
RF return as well. Multiple rules and layout issues all
John:
Look at the ppm (or however they express it) as to the sensitivity of the
frequency stability of the OCXO relative to Voltage input.
Say the oven power drops from 3 watts to 1 Watt as the oven comes up
to temperature. At 3 Volts, relative to 12 Volts, for a given resistance,
it is four
Graham,
Good points - yes, I have this part currently in the design: TPS75833KTTT
(LDO from TI) - putting another one down
(just) for the OCXO isn't a problem.
And a nice 12V rail isn't a problem either since this is for a radio with a
nice 12V source. Could I boost the 3.3V rail to
12V or
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