ADR1399 reference

[Andreas]

One of the thoughts was to be able to support up to 10 mA output current without major problems.

with 10 mA I would think about 4 Wire output.
with best regards
Andreas

[iMo]

One of the thoughts was to be able to support up to 10 mA output current without major problems.

with 10 mA I would think about 4 Wire output.
with best regards
Andreas

Also doublecheck the output buffer's capabilities - whether the buffer is able to provide those 10mA without a significant drop at the +10V output star.. (ie. the 10k base resistor and the 20ohm shunt sizing)..


@Andreas: 4w is needed, sure.. 10mA is a huge current. I had 16uV drop with the same buffer (but 25ohm shunt) with aprox 12mA load directly at the pcb's posts, with a ~15cm (EDIT: actually longer as I have there a ferrite bead with 2 or 3 turns) long 0.8mm dia (!) copper wiring from the pcb posts to the posts on the box I get ~160uV with 10mA. Not counting additional leads.. 

[DavidKo]

I'm not sure how much it is critical. For the start-up there is 200k resistor from the supply in "portable calibrator" on page 6.

[Kleinstein]

With the OPA202 the startup could indeed be an issue, as it has rail to rail outputs. Chances are it would still work even with just 1 diode vor the shift at the output, as the diode forward voltage for a small diode tends to be higher than transistor BE voltage. To be on the safe side, maybe have 2 diodes in series, so that the output would never go below some 0.6 V.

[DavidAzulay5000]

perfect 10
LM399AH
LT3042 OUTPUT 15V
LT1001
aluminum PCB

[branadic]

@ Andreas

Did you observe jumps on all your LCC packaged ADR1399? Is it already confirmed popcorn noise or could it also be what is known for some LTZ1000ACH and its glass bead filled die attach?
Can someone else report similar jumps on his devices?

-branadic-

[Andreas]

Hello Branadic,

as stated here:
https://www.eevblog.com/forum/metrology/adr1399-reference/msg4453792/#msg4453792

I have found popcorn noise up to 1.6 uV on every device during 1/f noise measurements.
Unfortunately this is so low that I cannot confirm this by absolute voltage measurements with my equipment.

The largest popcorn noise (> 1ppm at certain temperatures/times) on the same PCB is one LM399 from LT (LT#02).
This is well above my standard deviation of ~0.25 ppm for 7V measurements.

So now after proper packaging the only remaining issue is the rather large T.C. of the ADR1399LS8
(compared with a typical LM399 near room temperature).

with best regards

Andreas

[JodelJonny]

Hello,

the parts for my reference arrived and I successfully build it without major problems. Just that I stupidly ordered the SMD package ADR1399 :/
I made it fit with some copper wire. Not Ideal but the best I could do for now.
I'll likely build a second one in the future.

It has run for a few days now and seems stable at 10.02271V with very slight variation of the last digit.

I am neither equipped nor able to actually characterise its performance right now. That is the next project to figure out.

No worries, the ADR got some insulation after I took the picture.

Thanks for your help. I am happy with the result and this gives me a good starting point to dive deeper in the topic.

[iMo]

Is the D2 the zener? Btw., I've been always putting a diode in series with the zener (see my schematics around). Even often commented here the diode is redundant, you will see it in action when your output posts get shorted..

[JodelJonny]

D2 is a standard diode. There is no Zener.

[dietert1]

Looks great, already better than the AD evaluation board, that does not have a 10V gain stage.
The metal enclosure is connected to Gnd? One can use a small 50 or 100 Ohm resistor to do that. Or give it a "Guard" terminal.

Regards, Dieter

[Andreas]

Hello,

update of ADR1399LS8 ageing 1kHr after putting into Hammond enclosure:
see also
https://www.eevblog.com/forum/metrology/adr1399-reference/msg4737989/#msg4737989

The ADR1399LS8#01 - #04 are now stable (except for temperature drift which is large compared to the 2 LM399 which are running in parallel).
The LM399LT#01 - 02# in comparison are much more temperature stable.
But LM399LT#02 shows a rather large popcorn noise > 1 ppm

The ADR1399 seem to drift upwards by around 0.5 ppm/khr after 4.3 kHrs in total now.
The LM399 after 2.5 kHrs in total show nearly no ageing drift (except for popcorn).

with best regards

Andreas

[aronake]

Would anyone have kicad (or other circuti design program) or Gerber files to share for a ADR1399KEZ based circuit? Best if it have 10V boost stage, but if not, that would still be helpfull.

[JodelJonny]

I could post the KiCad, Gerber and BOM file for the circuit I build if that fits your need. But they are pretty messy since that was my first design in KiCad.
I would need at least a few days to clean up the most important errors.

[aronake]

I could post the KiCad, Gerber and BOM file for the circuit I build if that fits your need. But they are pretty messy since that was my first design in KiCad.
I would need at least a few days to clean up the most important errors.

That would be awesome! And I am sure many other here would appreciated that too!

[gamalot]

Got an interesting one, maybe it could be a good candidate for a 10V reference based on the ADR1399. 

https://www.vishay.com/docs/60002/osop.pdf

[Andreas]

Hello,

update of ADR1399LS8 ageing 2kHr after putting into Hammond enclosure and with temperature compensation:
see also
https://www.eevblog.com/forum/metrology/adr1399-reference/msg4809413/#msg4809413

The ADR have now 5.3 kHrs in total operating time.
The ADR1399LS8#01 - #03 are drifting slightly upwards ~0.5 ppm / kHr in average over the last 2 kHrs.
The ADR1399LS8#04 has nearly no ageing drift.

The LM399 after 3.5 kHrs in total show still nearly no ageing drift (except for popcorn noise).

The measurement gap around day 70 is due to T.C. measurements of all devices.
The repeated T.C. measurement (in ppm/K) shows nearly no change against previous measurement.

with best regards

Andreas

[Andreas]

Hello,

in the mean time I have built a 2nd PCB in a Hammond housing for ageing of the ADR1399 references.
And while waiting for the metal can packages which are delayed from month to month
I could not resist to do some T.C. testing with the 4 "fresh" LS8 devices on the pcb.

The PCB has been operated in total 8 hours within 4 weeks before this tests.
Since there was a relatively large initial ageing drift I had to wait some temperature cycles
until the T.C. could be measured with a reasonable ageing drift.
So total measuring time was 100 hrs.

here the results of the 4 devices on PCB #2
Again the T.C. of the LS8-packages is relatively high compared to typical LM399 devices.

with best regards

Andreas

[Conrad Hoffman]

I guess I need to ask, having bought one of the SMT versions a while back, is this reference really a good choice if you have room for a regular 399 or other device? I'm not seeing it as a "serious" reference to use as a lab standard or in a high precision instrument.

[Andreas]

Hello,

as always it depends on your needs:
- low noise (better than LM399)
- low T.C.  (my LM399 samples are better)
- low ageing drift (I am still evaluating but the ADR1399 seem to be better than the ADR1000A)

For me with 18-33 deg C in my "lab" the T.C. is a enemy.

with best regards

Andreas

[dietert1]

After buying the SMD ADR1399 evaluation i ended up building a 10 V gain stage - also as bootstrap for the reference. This includes a low pass filter and outer oven to keep everything at 38 °C. It performs very well. I have seen 0.2 ppm RMS over one month.
Our LTFLU references are better, as they are 4x zener arrays. I am wondering what happened to the 4x ADR1399 array designs shown before in this thread.

Regards, DIeter

Edit: After fixing a workstation i looked at the logs once more and the difference voltage between the references ADR1399 and LTFLU1 was 0.059 ppm RMS of hourly averages between 2023-04-02 and 2023-05-08.

[Andreas]

Hello,

update of ADR1399LS8 ageing 3kHr after putting into Hammond enclosure and with temperature compensation:
see also

https://www.eevblog.com/forum/metrology/adr1399-reference/msg4875467/#msg4875467

The ADR have now 6.3 kHrs in total operating time. Tempco is calculated out for the ageing curves.
The ADR1399LS8#01 - #03 are drifting slightly upwards ~2 ppm / 3 kHr in average over the last 3 kHrs.
The ADR1399LS8#04 has nearly no ageing drift.

with best regards

Andreas

[branadic]

Unfortunately, ADR1399KHZ delivery date is shifting each month by another month. Ordered in Feb 2023 this is the history of updated delivery dates so far:

MAR 28, 2023
MAI 02, 2023
MAI 09, 2023
MAI 16, 2023
JUN 20, 2023
JUL 14, 2023
JUN 26, 2023
JUL 03, 2023
JUL 07, 2023
JUL 14, 2023
JUL 21, 2023
AUG 01, 2023

Seems like ADI has some serious problems in getting them fabricated.
Luckily, some forum member was kind enough to send me a few samples and they will arrive within the next days, so I can proceed with my experiments soon.

-branadic-

[DavidKo]

During my order at 26th July 2022, the delivery date was unknown. At 28th November, they have sent update that ADR1399KHZ will be available 15th August 2023 (and ADR1399KEZ on stock). Ordered through Mouser.

[Andreas]

you are not alone
my order from Jan 22 is still waiting on delivery ...
with best regards
Andreas