[time-nuts] TS2100: From regular xtal to OCXO?

[Bruce Lane]

Fellow Clock-Tickers,

I've got a pair of Symmetricom TS2100's, both of which have the basic
TTL oscillator module for their reference oscillator. As other owners of
these units are probably aware, the board is also laid out for a couple
of different types of OCXO.

I've got what I believe are the correct OCXO's coming from an Ebay
vendor. They match the source voltage (12VDC), the control voltage
range, and the pinout.

My question is, do I need to make any configuration changes to the
2100's, in terms of jumpers or anything? Or is it literally a case of
swap-and-play?

Thanks much.

-- 
---
Bruce Lane, ARS KC7GR
http://www.bluefeathertech.com
kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)
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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[ed breya]

Before adding complexity of parallel devices or external passing, why 
not just try the old parallel-resistor trick? If the load takes a 
certain minimum current under all conditions, provide less than that via 
a resistor from the raw source to the regulated output, likewise under 
all conditions. The main regulator will still do its thing, but not have 
to supply all the current. You're just looking to get a little more 
margin between the spec current and actual load. The short-circuit 
current would be increased too, so take that into account.


Now some will say, "what about the ripple voltage from the raw supply 
causing ripple current going right to the output?" Depending on the 
regulator's characteristics, I think it should be able to handle it just 
fine - it's easy enough to hook it up and see how it works.


It would be good have OVP on the output regardless of the regulation 
scheme to protect the load if it's sensitive to OV. Obviously, the 
parallel resistor one could allow the voltage to go high if some load is 
lost, but the same can happen with a regulator failure too.


Ed

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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[John Miles]

> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of John
> Ackermann N8UR
>
> Reviving the conversation about superb voltage regulators, I am looking
> for one to run the analog and PLL bits of a high performance frequency
> synthesizer chip.
> 
> The current drain looks to be about 160-180 mA at 1.8 V, which is
> uncomfortably close to the limit for the LT3042 (200 mA).  The
> manufacturer's evaluation board uses a MAX8869, which appears to be
> nowhere in the LT3042's league, but will source 1 A.
> 
> Any recommendations for a 1.8 V regulator a little beefier than the
> LT3042, but with similar noise performance?

These days, the best RF synthesizer and clock generator chips include dedicated 
low-noise LDOs inside the package.  It's rarely worthwhile to use a quieter 
regulator than the manufacturer recommends, or one that's quieter than whatever 
is on their own demo board. 

One very nifty example is the LMK61E2, which I X-rayed a while back:
http://www.ke5fx.com/LMK61E2_30kVp_20s.png

The overall package is only about 1 cm square.  The synthesizer has its own 
die, while the input regulators and (presumably) their bypass caps are mounted 
directly above the Vdd input pad.  According to TI, the PSRR of the internal 
LDO that runs the analog section is better than 70 dB at offsets below 1 MHz.  
So you could even power it directly from a switcher, assuming you keep a leash 
on its harmonics. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Use the LT3042 for retrofit?

[Bob kb8tq]

Hi

The gotcha is not on the manufacturing end. When you show up with a dual ground 
pin part, the OEM asks: Where do I tell the PCB layout guys to put the other 
ground?
The answer always comes back to “there’s only one ground plane, they will both 
connect
to the same plane.”.  If you get past that, the somewhat surprising next layer 
is that 
temperature performance maybe isn’t that big a deal to them ….

Bob

> On Mar 21, 2018, at 6:03 PM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
> [context is EFC control voltage]
>> Generally, the biggest factor is the voltage drop from the oven current
>> getting into the EFC “loop”. Its actually pretty hard to keep them separate.
> 
> Is there a fundamental problem, or is it just that everybody uses historical 
> footprints that don't have separate ground pins?
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] ULN regulator with more current capability than LT3042?

[Gerhard Hoffmann]

Am 20.03.2018 um 10:09 schrieb Attila Kinali:

Hoi Gerhard,

On Sun, 18 Mar 2018 21:41:28 +0100
Gerhard Hoffmann  wrote:


Use the LT3042 with an external power transistor, such as D44VH10G:

<
https://www.flickr.com/photos/137684711@N07/29197476530/in/album-72157662535945536/
  >

Performance is about the same as the LT3042 alone. That is exactly the
circuit from the data sheet

Have you measured it's dynamic performance?
I did some spice simulations some time ago and noticed that there are
some load conditions where this circuit is very close to oscillation
(ie load changes lead to heavy ringing)of course, this is under
the assumption that the spice model of the LT3042 is accurate in that
regard.

No, I didn't. My oscillators are quite boring loads for a regulator.

regards, Gerhard

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Re: [time-nuts] Use the LT3042 for retrofit?

[Gerhard Hoffmann]

Am 21.03.2018 um 23:03 schrieb Hal Murray:

kb...@n1k.org said:
[context is EFC control voltage]

Generally, the biggest factor is the voltage drop from the oven current
getting into the EFC “loop�. Its actually pretty hard to keep them separate.

Is there a fundamental problem, or is it just that everybody uses historical
footprints that don't have separate ground pins?


The HP 10811 has separate pins for oscillator and oven, for
power and gnd, and 2 of them for each of the four.

regards, Gerhard
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Re: [time-nuts] Use the LT3042 for retrofit?

[Hal Murray]

kb...@n1k.org said:
[context is EFC control voltage]
> Generally, the biggest factor is the voltage drop from the oven current
> getting into the EFC “loop”. Its actually pretty hard to keep them 
> separate.

Is there a fundamental problem, or is it just that everybody uses historical 
footprints that don't have separate ground pins?

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Use the LT3042 for retrofit?

[Bob kb8tq]

Hi

You can either do the math … yuck …. or just try it. It turns out that with a 
“normal” sort of
EFC sensitivity (< 1 ppm / V) on a “normal” frequency OCXO ( <30 MHz) , the 
voltage can have a 
bit of noise on it and the phase noise of the device will not suffer. Simply 
put - you can run it 
with a 78L05 and the phase noise will be the same as with a short. 

Since the phase modulation rolls off as 1/F for a flat noise spectrum, the 
noise on the EFC 
“chases” the phase noise floor as frequency increases. Toss in an internal 
bypass on the EFC
line and it goes down even faster. 

If you get into OCXO’s that are more like VCO’s then things aren’t quite so 
easy….

Now, this is just talking about phase noise. If you look at stability, indeed a 
finite delta V on the EFC
will change the frequency of the OCXO. Generally, the biggest factor is the 
voltage drop from the
oven current getting into the EFC “loop”. Its actually pretty hard to keep them 
separate. Unless 
you can split them apart, they will limit your heroic efforts on EFC stability. 
Our 1 ppm / V OCXO 
above moves 1 ppb / 1 mv. If you are after a ppt, you need 1 uV of EFC “ground 
isolation”. 

Bob

> On Mar 20, 2018, at 10:24 PM, Perry Sandeen via time-nuts 
>  wrote:
> 
> Yo Dudes,
> Should one consider retrofitting  HP 105's,  Austron 1250's or HP 10811 power 
> supplies with the LT3042 for better performance?  The price is modest.  The 
> HP 10811 suggested PS for the EFC is a 723 circuit that spedc's 6 microvolts 
> ripple IIRC.
> Regards,
> Perrier
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