Re: [time-nuts] Surface Mount OCXO Questions

[John C. Westmoreland, P.E.]

Bob,

These are good suggestions.  I will probably end up doing 1) and 2) you
have outlined above.

Thanks!
John W.



On Thu, Oct 31, 2013 at 7:51 AM, Robert LaJeunesse <
rlajeune...@sbcglobal.net> wrote:

> A couple tricks I've learned along the way: 1) If using a switching supply
> is required to get a higher voltage, follow it with a good LDO to reduce
> the noise level. I've done this successfully for powering handheld radio
> microphones with built-in amplification, video amplifiers, and for
> operating a GPS receiver and antenna. 2) If there is a possible ground
> current path problem, break the ground path by using a unity gain
> "difference" amplifier like the AD8276, or a difference amplifier with gain
> like the INA145. The input is differential to the source signal, and the
> output has a moderately high impedance reference terminal that can be tied
> directly to the load device ground pin. I use this technique all the time
> to keep down the noise when driving remote analog loads that have large
> ground currents themselves. (Picture a 110W 40MHz transmitter running off
> 12V, at the bottom of a stack of other transceivers in the trunk of a
> police car - with 40A of
>  lights flashing, etc.)
>
> Bob LaJeunesse
>
>
> >
> > From: "John C. Westmoreland, P.E." 
> >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 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 since this is for a radio with
> a
> >nice 12V source.  Could I boost the 3.3V rail to
> >12V or maybe 5V to 12V - sure - but your point about the switcher is well
> >taken and I agree.  Having a nice, fat, analog
> >ground plane isn't a problem either.
> >
> >And, this is just a 'dev' board so we can do what we need to make the OCXO
> >work as good as possible.
> >
> >From their spec sheet:  '... the supply voltage sensitivity and load
> >sensitivity is 5E-11 for a 5 % change in voltage or
> >load impedance.'
> >
> >Thanks,
> >John
> >
> >
> >
> >
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Re: [time-nuts] Surface Mount OCXO Questions

[Robert LaJeunesse]

A couple tricks I've learned along the way: 1) If using a switching supply is 
required to get a higher voltage, follow it with a good LDO to reduce the noise 
level. I've done this successfully for powering handheld radio microphones with 
built-in amplification, video amplifiers, and for operating a GPS receiver and 
antenna. 2) If there is a possible ground current path problem, break the 
ground path by using a unity gain "difference" amplifier like the AD8276, or a 
difference amplifier with gain like the INA145. The input is differential to 
the source signal, and the output has a moderately high impedance reference 
terminal that can be tied directly to the load device ground pin. I use this 
technique all the time to keep down the noise when driving remote analog loads 
that have large ground currents themselves. (Picture a 110W 40MHz transmitter 
running off 12V, at the bottom of a stack of other transceivers in the trunk of 
a police car - with 40A of
 lights flashing, etc.) 

Bob LaJeunesse


>
> From: "John C. Westmoreland, P.E." 
>To: Discussion of precise time and frequency measurement  
>Sent: 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 since this is for a radio with a
>nice 12V source.  Could I boost the 3.3V rail to
>12V or maybe 5V to 12V - sure - but your point about the switcher is well
>taken and I agree.  Having a nice, fat, analog
>ground plane isn't a problem either.
>
>And, this is just a 'dev' board so we can do what we need to make the OCXO
>work as good as possible.
>
>From their spec sheet:  '... the supply voltage sensitivity and load
>sensitivity is 5E-11 for a 5 % change in voltage or
>load impedance.'
>
>Thanks,
>John
>
>
>
>
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Re: [time-nuts] Surface Mount OCXO Questions

[Jim Lux]

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 3.3V or 5V, and have 15V tuning 
ranges.  It's a real pain when you're looking to swap VCOs in a PLL to 
change the tuning range in a breadboard.


Minicircuits ROS-3710 is a fine example.. 5V operation, tuning range 0.5-13V

ROS-3388-219 is the same.

It's because the tune port goes right to the varactor, which is, not so 
oddly, DC blocked from the amplifier circuit running on 5V


To put this in perspective, you can see a change on a normal 12V part
grounding it on the top side of a PC board vs grounding it on the
bottom side of the board. The 0.032” of solid ground lead has enough
drop to be noticeable.


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Re: [time-nuts] Surface Mount OCXO Questions

[Bob Camp]

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 grounding 
it on the top side of a PC board vs grounding it on the bottom side of the 
board. The 0.032” of solid ground lead has enough drop to be noticeable. 

Bob

On Oct 30, 2013, at 9:47 PM, Graham / KE9H  wrote:

> 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 time the Voltage change due to the higher currents, and an 
> additional
> four times the percentage of the operating Voltage as a ratio.  So additional
> design consideration for Voltage control/stabilization is needed.
> 
> If you have a solid (wide, thick, multi-layer) ground, then that can
> work.  To reduce the voltage drop feeding the OCXO, you might consider
> putting a dedicated LDO regulator, right at the OCXO, that shares the ground
> reference with the OCXO, so any voltage drop in the feed side is removed,
> as well as any Voltage variability with current in the ground system.
> 
> As to why they are selling the 3.3V part, they probably started selling it
> before they had some customers get into performance issues per the above.
> But once offered, they have to continue to support their customers.
> 
> I think they are just telling you that it is somewhere between 4 and 16 times
> easier to get the full performance out of the part with a 12 Volt power feed
> than a 3 Volt power feed, not that you can't get full performance with a 3.3V 
> feed.
> 
> I am sure their parts meet specs, you just need to understand them.
> 
> P.S. - I would stick with linear regulators feeding the OCXO, not a switcher.
> 
> --- Graham
> 
> ==
> 
> On 10/30/2013 7:37 PM, John C. Westmoreland, P.E. wrote:
>> 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 voltage for the oven.
>> 
>> Have any of you experienced this?  Makes me wonder a little why they offer
>> the 3.3V part.  It would seem good layout can control any possibility of
>> ground loops becoming a problem.
>> 
>> Thanks and Regards,
>> John W./AJ6BC
>> 
>> 
>> 
>> 
>> On Wed, Oct 30, 2013 at 6:54 AM, Graham / KE9H wrote:
>> 
>>> 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 oven.  I have seen all three cases.  As usual, it is suggested that you
>>> read the [] manual.
>>> 
>>> Best regards,
>>> --- Graham / KE9H
>>> 
>>> ==
>>> 
>>> 
>>> 
>>> On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote:
>>> 
 Hello,
 
 I was wondering if I could get some recommendations on surface mount
 OCXO's
 vs. the traditional through hole.
 
 I was also wondering on the board layout - if you found it necessary to
 leave a thermal moat so to speak - and what worked best.  Maybe the OCXO
 has an internal air barrier that maybe would make this unnecessary - not
 sure.
 
 Your input and experience appreciated.
 
 Thanks,
 John Westmoreland
> 
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Re: [time-nuts] Surface Mount OCXO Questions

[John C. Westmoreland, P.E.]

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 maybe 5V to 12V - sure - but your point about the switcher is well
taken and I agree.  Having a nice, fat, analog
ground plane isn't a problem either.

And, this is just a 'dev' board so we can do what we need to make the OCXO
work as good as possible.

>From their spec sheet:  '... the supply voltage sensitivity and load
sensitivity is 5E-11 for a 5 % change in voltage or
load impedance.'

Thanks,
John



On Wed, Oct 30, 2013 at 6:47 PM, Graham / KE9H wrote:

> 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 time the Voltage change due to the higher currents, and an
> additional
> four times the percentage of the operating Voltage as a ratio.  So
> additional
> design consideration for Voltage control/stabilization is needed.
>
> If you have a solid (wide, thick, multi-layer) ground, then that can
> work.  To reduce the voltage drop feeding the OCXO, you might consider
> putting a dedicated LDO regulator, right at the OCXO, that shares the
> ground
> reference with the OCXO, so any voltage drop in the feed side is removed,
> as well as any Voltage variability with current in the ground system.
>
> As to why they are selling the 3.3V part, they probably started selling it
> before they had some customers get into performance issues per the above.
> But once offered, they have to continue to support their customers.
>
> I think they are just telling you that it is somewhere between 4 and 16
> times
> easier to get the full performance out of the part with a 12 Volt power
> feed
> than a 3 Volt power feed, not that you can't get full performance with a
> 3.3V feed.
>
> I am sure their parts meet specs, you just need to understand them.
>
> P.S. - I would stick with linear regulators feeding the OCXO, not a
> switcher.
>
> --- Graham
>
> ==
>
>
> On 10/30/2013 7:37 PM, John C. Westmoreland, P.E. wrote:
>
>> 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 voltage for the oven.
>>
>> Have any of you experienced this?  Makes me wonder a little why they offer
>> the 3.3V part.  It would seem good layout can control any possibility of
>> ground loops becoming a problem.
>>
>> Thanks and Regards,
>> John W./AJ6BC
>>
>>
>>
>>
>> On Wed, Oct 30, 2013 at 6:54 AM, Graham / KE9H > >wrote:
>>
>>  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 oven.  I have seen all three cases.  As usual, it is suggested that
>>> you
>>> read the [] manual.
>>>
>>> Best regards,
>>> --- Graham / KE9H
>>>
>>> ==
>>>
>>>
>>>
>>> On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote:
>>>
>>>  Hello,

 I was wondering if I could get some recommendations on surface mount
 OCXO's
 vs. the traditional through hole.

 I was also wondering on the board layout - if you found it necessary to
 leave a thermal moat so to speak - and what worked best.  Maybe the OCXO
 has an internal air barrier that maybe would make this unnecessary - not
 sure.

 Your input and experience appreciated.

 Thanks,
 John Westmoreland

>>>
> __**_
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> mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] Surface Mount OCXO Questions

[Graham / KE9H]

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 time the Voltage change due to the higher currents, and an 
additional
four times the percentage of the operating Voltage as a ratio.  So 
additional

design consideration for Voltage control/stabilization is needed.

If you have a solid (wide, thick, multi-layer) ground, then that can
work.  To reduce the voltage drop feeding the OCXO, you might consider
putting a dedicated LDO regulator, right at the OCXO, that shares the ground
reference with the OCXO, so any voltage drop in the feed side is removed,
as well as any Voltage variability with current in the ground system.

As to why they are selling the 3.3V part, they probably started selling it
before they had some customers get into performance issues per the above.
But once offered, they have to continue to support their customers.

I think they are just telling you that it is somewhere between 4 and 16 
times

easier to get the full performance out of the part with a 12 Volt power feed
than a 3 Volt power feed, not that you can't get full performance with a 
3.3V feed.


I am sure their parts meet specs, you just need to understand them.

P.S. - I would stick with linear regulators feeding the OCXO, not a 
switcher.


--- Graham

==

On 10/30/2013 7:37 PM, John C. Westmoreland, P.E. wrote:

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 voltage for the oven.

Have any of you experienced this?  Makes me wonder a little why they offer
the 3.3V part.  It would seem good layout can control any possibility of
ground loops becoming a problem.

Thanks and Regards,
John W./AJ6BC




On Wed, Oct 30, 2013 at 6:54 AM, Graham / KE9H wrote:


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 oven.  I have seen all three cases.  As usual, it is suggested that you
read the [] manual.

Best regards,
--- Graham / KE9H

==



On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote:


Hello,

I was wondering if I could get some recommendations on surface mount
OCXO's
vs. the traditional through hole.

I was also wondering on the board layout - if you found it necessary to
leave a thermal moat so to speak - and what worked best.  Maybe the OCXO
has an internal air barrier that maybe would make this unnecessary - not
sure.

Your input and experience appreciated.

Thanks,
John Westmoreland


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Re: [time-nuts] Surface Mount OCXO Questions

[Bob Camp]

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 collide at that pin…..

Bob

On Oct 30, 2013, at 9:02 PM, John C. Westmoreland, P.E. 
 wrote:

> 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 - yep.  This is exactly why I am asking
> these questions.
> 
> Even in manufacturer's recommended layout instructions you can find
> mistakes.  Unless you have a dev board that you have used and have the
> gerbers from
> that board so you know exactly how that part behaves with that layout - you
> cannot know for sure you have a sound layout for your design.  You also
> have
> to be careful with board material, dielectrics, and copper weight, not to
> mention controlled impedances.
> 
> Remember the early days of DC/DC converters?
> 
> Thanks!
> John / AJ6BC
> 
> 
> 
> On Wed, Oct 30, 2013 at 5:52 PM, Bob Camp  wrote:
> 
>> 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
>> designed it in …..
>> 
>> Bob
>> 
>> On Oct 30, 2013, at 8:37 PM, John C. Westmoreland, P.E. <
>> j...@westmorelandengineering.com> wrote:
>> 
>>> 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 voltage for the oven.
>>> 
>>> Have any of you experienced this?  Makes me wonder a little why they
>> offer
>>> the 3.3V part.  It would seem good layout can control any possibility of
>>> ground loops becoming a problem.
>>> 
>>> Thanks and Regards,
>>> John W./AJ6BC
>>> 
>>> 
>>> 
>>> 
>>> On Wed, Oct 30, 2013 at 6:54 AM, Graham / KE9H >> wrote:
>>> 
 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 oven.  I have seen all three cases.  As usual, it is suggested that
>> you
 read the [] manual.
 
 Best regards,
 --- Graham / KE9H
 
 ==
 
 
 
 On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote:
 
> Hello,
> 
> I was wondering if I could get some recommendations on surface mount
> OCXO's
> vs. the traditional through hole.
> 
> I was also wondering on the board layout - if you found it necessary to
> leave a thermal moat so to speak - and what worked best.  Maybe the
>> OCXO
> has an internal air barrier that maybe would make this unnecessary -
>> not
> sure.
> 
> Your input and experience appreciated.
> 
> Thanks,
> John Westmoreland
> __**_
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>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> and follow the instructions there.
> 
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 __**_
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 mailman/listinfo/time-nuts<
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 and follow the instructions there.
 
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Re: [time-nuts] Surface Mount OCXO Questions

[John C. Westmoreland, P.E.]

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 - yep.  This is exactly why I am asking
these questions.

Even in manufacturer's recommended layout instructions you can find
mistakes.  Unless you have a dev board that you have used and have the
gerbers from
that board so you know exactly how that part behaves with that layout - you
cannot know for sure you have a sound layout for your design.  You also
have
to be careful with board material, dielectrics, and copper weight, not to
mention controlled impedances.

Remember the early days of DC/DC converters?

Thanks!
John / AJ6BC



On Wed, Oct 30, 2013 at 5:52 PM, Bob Camp  wrote:

> 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
> designed it in …..
>
> Bob
>
> On Oct 30, 2013, at 8:37 PM, John C. Westmoreland, P.E. <
> j...@westmorelandengineering.com> wrote:
>
> > 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 voltage for the oven.
> >
> > Have any of you experienced this?  Makes me wonder a little why they
> offer
> > the 3.3V part.  It would seem good layout can control any possibility of
> > ground loops becoming a problem.
> >
> > Thanks and Regards,
> > John W./AJ6BC
> >
> >
> >
> >
> > On Wed, Oct 30, 2013 at 6:54 AM, Graham / KE9H  >wrote:
> >
> >> 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 oven.  I have seen all three cases.  As usual, it is suggested that
> you
> >> read the [] manual.
> >>
> >> Best regards,
> >> --- Graham / KE9H
> >>
> >> ==
> >>
> >>
> >>
> >> On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote:
> >>
> >>> Hello,
> >>>
> >>> I was wondering if I could get some recommendations on surface mount
> >>> OCXO's
> >>> vs. the traditional through hole.
> >>>
> >>> I was also wondering on the board layout - if you found it necessary to
> >>> leave a thermal moat so to speak - and what worked best.  Maybe the
> OCXO
> >>> has an internal air barrier that maybe would make this unnecessary -
> not
> >>> sure.
> >>>
> >>> Your input and experience appreciated.
> >>>
> >>> Thanks,
> >>> John Westmoreland
> >>> __**_
> >>> time-nuts mailing list -- time-nuts@febo.com
> >>> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> >>> mailman/listinfo/time-nuts<
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
> >>> and follow the instructions there.
> >>>
> >>>
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Re: [time-nuts] Surface Mount OCXO Questions

[Bob Camp]

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 designed it in …..

Bob

On Oct 30, 2013, at 8:37 PM, John C. Westmoreland, P.E. 
 wrote:

> 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 voltage for the oven.
> 
> Have any of you experienced this?  Makes me wonder a little why they offer
> the 3.3V part.  It would seem good layout can control any possibility of
> ground loops becoming a problem.
> 
> Thanks and Regards,
> John W./AJ6BC
> 
> 
> 
> 
> On Wed, Oct 30, 2013 at 6:54 AM, Graham / KE9H wrote:
> 
>> 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 oven.  I have seen all three cases.  As usual, it is suggested that you
>> read the [] manual.
>> 
>> Best regards,
>> --- Graham / KE9H
>> 
>> ==
>> 
>> 
>> 
>> On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote:
>> 
>>> Hello,
>>> 
>>> I was wondering if I could get some recommendations on surface mount
>>> OCXO's
>>> vs. the traditional through hole.
>>> 
>>> I was also wondering on the board layout - if you found it necessary to
>>> leave a thermal moat so to speak - and what worked best.  Maybe the OCXO
>>> has an internal air barrier that maybe would make this unnecessary - not
>>> sure.
>>> 
>>> Your input and experience appreciated.
>>> 
>>> Thanks,
>>> John Westmoreland
>>> __**_
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/**
>>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>> 
>>> 
>> __**_
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>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
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Re: [time-nuts] Surface Mount OCXO Questions

[John C. Westmoreland, P.E.]

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 voltage for the oven.

Have any of you experienced this?  Makes me wonder a little why they offer
the 3.3V part.  It would seem good layout can control any possibility of
ground loops becoming a problem.

Thanks and Regards,
John W./AJ6BC




On Wed, Oct 30, 2013 at 6:54 AM, Graham / KE9H wrote:

> 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 oven.  I have seen all three cases.  As usual, it is suggested that you
> read the [] manual.
>
> Best regards,
> --- Graham / KE9H
>
> ==
>
>
>
> On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote:
>
>> Hello,
>>
>> I was wondering if I could get some recommendations on surface mount
>> OCXO's
>> vs. the traditional through hole.
>>
>> I was also wondering on the board layout - if you found it necessary to
>> leave a thermal moat so to speak - and what worked best.  Maybe the OCXO
>> has an internal air barrier that maybe would make this unnecessary - not
>> sure.
>>
>> Your input and experience appreciated.
>>
>> Thanks,
>> John Westmoreland
>> __**_
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/**
>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
> __**_
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] Surface Mount OCXO Questions

[Graham / KE9H]

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 oven.  I have seen all three cases.  As usual, it is suggested that you
read the [] manual.

Best regards,
--- Graham / KE9H

==


On 10/29/2013 9:18 PM, John C. Westmoreland, P.E. wrote:

Hello,

I was wondering if I could get some recommendations on surface mount OCXO's
vs. the traditional through hole.

I was also wondering on the board layout - if you found it necessary to
leave a thermal moat so to speak - and what worked best.  Maybe the OCXO
has an internal air barrier that maybe would make this unnecessary - not
sure.

Your input and experience appreciated.

Thanks,
John Westmoreland
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Re: [time-nuts] Surface Mount OCXO Questions

[Bob Camp]

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. 
 wrote:

> Hello,
> 
> I was wondering if I could get some recommendations on surface mount OCXO's
> vs. the traditional through hole.
> 
> I was also wondering on the board layout - if you found it necessary to
> leave a thermal moat so to speak - and what worked best.  Maybe the OCXO
> has an internal air barrier that maybe would make this unnecessary - not
> sure.
> 
> Your input and experience appreciated.
> 
> Thanks,
> John Westmoreland
> ___
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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[time-nuts] Surface Mount OCXO Questions

[John C. Westmoreland, P.E.]

Hello,

I was wondering if I could get some recommendations on surface mount OCXO's
vs. the traditional through hole.

I was also wondering on the board layout - if you found it necessary to
leave a thermal moat so to speak - and what worked best.  Maybe the OCXO
has an internal air barrier that maybe would make this unnecessary - not
sure.

Your input and experience appreciated.

Thanks,
John Westmoreland
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