AD587LW - 10V precision travel standard

[Andreas]

Hello,

I added a 11V TVS diode some weeks ago (see red circle) which has low leakage @10V to protect the output against ESD and (hopefully since I did not actually test it) against a current limited calibrator (if shorted accidently).

As far as I can see the output voltage has not changed by adding the diodes on all 4 samples of AD587LW

For AD587LW#01 + #02 I have now 1 year of ageing data against my LTZ1000s (from which LTZ1000#4 is the most stable).

AD587LW#01 clearly fails my 2 ppm/year target. Its more like 3.5 ppm/year against my LTZ#4.
And ageing also does not look like it will slow down the next time. So I really think that I should do some artificial ageing measures.

The other references are much more stable.
AD587LW#02 is more or less a seasonal change +/- 0.5 ppm against LTZ#4. So within my 2 ppm/year limit.
I guess that this is due to humidity swelling of the EPOXY PCB which influences the AD587LQ reference.
And I think I should exclude LTZ#5 from the averaged diagrams as it spoils the average due to its ageing drift.


with best regards

Andreas

[iMo]

https://assets.nexperia.com/documents/data-sheet/PTVSXP1UP_SER.pdf

[Andreas]

Hello,

and the remaining references:

AD587LWB#03: This guy is somewhat suffering from the 2nd order T.C. which could not fully be compensated. So a temperature dependant drift +/- 1ppm over the last months is visible (so within the planned +/-2 ppm for temperature). And it is obvious that it will meet 1 year ageing drift of less than 2 ppm.

AD587LWB#04: It took long time from first measurement until I had calibrated T.C. + full scale on this sample. So only half year data since calibration (day 0).  Ageing drift was -0.5 ppm immediately after calibration.  But since then the device is very stable.

with best regards

Andreas

[Andreas]

Hello,

I made a little instruction leaflet for the AD587LW reference. (see attachment).

with best regards

Andreas

[Magnificent Bastard]

Sadly, I must report that one of the very best non-ovenized references in the world, the AD587, has transitioned to NRND [Not Recommended for New Designs].  It's now only a matter of time before it goes to EOL [End Of Life].

 

[Andreas]

Hello,

and the 2nd best one the 5V brother AD586 is now also NRND.
They are crazy.

with best regards

Andreas

[Macbeth]

Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?

[Magnificent Bastard]

Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?

There are an awful lot of LM399's that go into DMMs, so I don't foresee them killing that-- but the LTZ1000 simply does not have enough sales to justify keeping it in the lineup.  If they kill the LTZ1000, that will be a day of mourning for me...  Keysight will have to scramble for a new "super reference" for some of it's high end meters.  There are some manufacturers of voltage references (and other test equipment) that will have to do the same.  This is what happens when the "cake eaters" start making engineering decisions-- disasters ahead!

 

The AD587 was the last great unheated reference (with low LF noise) that you could buy in a hermetic package.  This decision might cause T.I. to fire up the hermetic packaging line for the REF102-- not as low LF noise as the AD587, but still a good part if you can get it in a hermetic package (that was discontinued long ago).

 

[3roomlab]

I think the next area of exploration is a cooler temperature instead of hotter
in the pickering pdf where they show low temperature drift advantage, there is a plotted point where it is 11k/1k 
maybe we just need a sweet spot low temperature which forces the drift to stop
maybe a new LTZ with TEC inside instead of heating, it hold the die at maybe -10C. maybe it will never drift or 1ppm per 10 years.

Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?

actually thinking about the history of rivalry, isnt AD the ones dishing out fake stability specifications many years ago?

[Andreas]

I did it:  I put 2 of the references in the freezer over night  

the good news: they survived (packed only into a plastic bag to reduce condensing water) at -19 deg C setpoint temperature.

The other morning the battery indicator blinked: the reference is still running.

The bad news

AD587LW#01 drifted -4.8 ppm
AD587LW#03 drifted -6.2 ppm

against last measurement from sunday. (obviously hysteresis)

so this is a strong indicator that shipping during winter is not the best idea.
And obviously a star pattern is needed to check the reference after each travel.

How long will it need to remove the hysteresis without heating?

with best regards

Andreas

[3roomlab]

you going to try 8hr "degauss" ?

[Andreas]

you going to try 8hr "degauss" ?

Hello,

what do you mean with 8hr degauss?

of course I waited several hours from morning to evening until I measured the voltage output under room temperature conditions.
So I think I will have the offset for several months.

with best regards

Andreas

[FriedLogic]

How long will it need to remove the hysteresis without heating?

For a 'winter transfer reference' I'm not sure if you want to remove it.

The question might be more: how do you maintain it?
It's not really the same thing a bench reference that never sees anything but room temperature.

I find that doing a wide range temperature test on a reference which has not had this done on it recently can cause a shift, but subsequent cycles cause much less.

My thinking is that maybe if a reference might get low temperatures, it may be better to always or regularly give it a low temperature. There might be more variation than a reference which never gets wide temperature swings, but it might also get rid of large jumps in the output voltage.

I have plenty 587LQ's to play with, so I can set something up to test how they behave. I'm thinking of doing that with some LM399's too.

[3roomlab]

Hello,

what do you mean with 8hr degauss?


Andreas

the hot cold hot cold cycling?

[Echo88]

Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?

There are an awful lot of LM399's that go into DMMs, so I don't foresee them killing that-- but the LTZ1000 simply does not have enough sales to justify keeping it in the lineup.

Who told you how much they sell and if its profitable to Analog to produce them?

[Magnificent Bastard]

Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?

There are an awful lot of LM399's that go into DMMs, so I don't foresee them killing that-- but the LTZ1000 simply does not have enough sales to justify keeping it in the lineup.

Who told you how much they sell and if its profitable to Analog to produce them?

My Linear Tech (now Analog) Rep.  He didn't exactly come right out and SAY that, but "reading between the lines" of what he DID say is how I arrived at that conclusion.  This was said just before the Analog takeover.  Analog is a vastly different company than it used to be, and is a vastly different company than Linear Tech used to be-- I don't think they would hesitate one second to drop a device from their lineup if it was losing money-- and ESPECIALLY if they had to pump a lot of money into an old fab just to keep it going, so that a few old parts can continue to be produced.  The only thing that is saving us is contractual obligations-- which I am not privy to-- but I know they must exist.  One good place to find out is Keysight-- they would know if there are rumors about these parts going NRND.  Keysight would have to scramble to come up with an alternative to the LTZ1000 and the LM399--- I have something in mind, but to think Keysight would listen to ME is laughable.

[Crossphased]

How do you guys feel about AD588? Looking at specs it has better tempco than AD587, and slightly lower p-p noise. Its also available in Cerdip, although it is more pricey than AD587. Its pin programmable to +10,+5, +-5, -10  so it can potentially fill in for the AD586 or AD587. Anybody have experience with this ref?

[Andreas]

How do you guys feel about AD588? Looking at specs it has better tempco than AD587, and slightly lower p-p noise. Its also available in Cerdip, although it is more pricey than AD587. Its pin programmable to +10,+5, +-5, -10  so it can potentially fill in for the AD586 or AD587. Anybody have experience with this ref?

Hello,

not myself but Lars reported on 25.11.2015 on "volt-nuts" about the AD688:
https://www.mail-archive.com/volt-nuts@febo.com/msg02662.html
Of course it is only a single sample and "popcorn noise" can occur on every reference.
But external temperature compensation seems to be difficult.

But I would only use a AD588/688 if I really need dual reference voltages.
And I would shurely not use the internal OP-Amps (1uV/K) for generating the buffered outputs.

with best regards

Andreas

[Andreas]

Hello,

on our volt nut meeting in Stuttgart I got another 2 traceable calibrations for my best 2 devices AD587LW#02 and AD587LW#04.
One against freshly calibrated 3458A from Branadic. The other as transfer in 10V range of 3458A compared to the Fluke 7000.

Attached you find the diagrams with the measurement uncertainities.
It seems that AD587LW#02 has nearly no ageing drift whereas AD587LW#04 drifted 1 ppm down during calibrations.

with best regards

Andreas

[Andreas]

Hello,

how time passes by ...
in the mean time I have new traceable calibrations for AD587LW#2 and #4.
Unfortunately with wider uncertainity.

with best regards

Andreas

[Andreas]

Hello,

there is no noise or other things in this chart.
These are calibrations against different calibrated Instruments with different accuracy along the calibration chain.
The largest width is the uncertainity of the (2 different) Fluke 5520A´s together with the uncertainity of their calibration.

with best regards

Andreas

[Andreas]

Hello,

again: how time passes by ...
in the mean time I have new traceable calibrations for AD587LW#2 and #4.
(Thanks to branadic)

this time I am showing only the calibrations against 3458B (option 02)
with either 1 day or 90 day + calibration uncertainity

Drift of AD587LW#2 is +1.4 ppm over 2.6 years
Drift of AD587LW#4 is -0.9 ppm over 2.6 years

So not bad to the "design spec" of 2 ppm/year

with best regards

Andreas

[guenthert]

Huh?  The measurements of January 2020 got lost?

[Kleinstein]

The data from january 2020 are with a rather high incertainty (e.g. +-10 ppm) - so they would not really help much and fit the scale.

[Andreas]

Huh?  The measurements of January 2020 got lost?

Hello,

Nothing gets really lost.
I think selecting the calibration points with low uncertainity is better for drift estimations.

Attached all calibrations.
But be aware:
a) On measurements of 06.06.2020 we had a guard loop between 2 parallel instruments.
So the values here are ~1-2 ppm worse. (have verified this with my weekly measurements against 24Bit ADC16)

b) The measurement against Fluke7000 are not direct but as sequential ratio measurement.
So there may be additional measurement setup errors.

c) the measurements against Fluke 5520A is differential with a 34401A as Null-Voltmeter.
   And I cannot guarantee that it is always the same Fluke 5520A.
   
with best regards

Andreas