ADR1001 - Ovenized Voltage Reference System

[MiDi]

LTspice misses something - it loads the OPAx189 part into the schematics, but I get
Fatal Error: Unknown subcircuit called in:
   xu1 n007 out n001 0 n005 %userprofile%\documents\ltspicexvii\lib\sub\contrib\ti\opax189.lib opax189

OPAx189.asy fixed, seems "SYMATTR Value2 OPAx189" is mandatory

[iMo]

Thanks MiDi we have got the first OPA189 buffer AC sim.. 

[Villain]

I ordered some boards on jlcpcb now and gonna make a digikey order today to populate the boards. If adr1001 chips, boards and components arrive in time i could turn the boards on before new year. But i have 3 week vacation now 

Happy holidays to everyone that reads this!

[mawyatt]

Thanks MiDi we have got the first OPA189 buffer AC sim.. 

In actual use you might consider adding a small "protection" resistor in series with the Op-Amp - input, since this is "exposed" directly to the Output as shown in the schematic.

For added protection for reverse polarity a shunt diode across the output and Overvoltage protection a diode to the +15V supply (which may need a Shunt Zener and/or reverse diode to regulator input).

Anyway, these suggestions are just for protection against abuse which isn't necessary in most cases for the folks here.

Trying to get our hands on a ADR1001 to play around with, left a note at Analog Devices requesting such.

Best,

[iMo]

I plan to wire a transil (12V) at the output.. I've got one already, but they sold me a bipolar one. It starts to conduct at some 11.5V, that is good. Before that I can see some uAmps through it. The Q is how the transil contributes to the noise then.. I already soldered an 18V transil at the power input of the board. The board has none voltage regulator on it. The protection resistor at the OPA's inv_input could be done too..

PS: I wish all the people here to get the samples under the Christmas tree, it is really a great gift to play with during the holidays !!! 

[iMo]

myADR1001 sandwich.. The same foam block from the bottom..

[sahko123]

I would say you should get a denser foam. By the looks of it thats very light weight foam and might not do anything but stop drafts

[iMo]

Another night run of the sandwich this time. First part on the free air, then put into an insulated box. The 12V TVS on the output, power 14.345V (the set voltage of the 723 power module which will be used with it). The free air temperature measured far of the sandwich, and in the box the sensor touching the foam. The next step is the LM35 will be soldered directly on the pcb (being the most expensive part there on the pcb  ).
PS: The LM35 mounted on the board, shows some 2C more in the box than the previous loose one, good. That is all, no other messing with the sandwitch, it will be put into a styrofoam insulation and put into a new nice box together with the psu (thus something similar to the Fluke 732D  )..

[iMo]

Ok, myADR1001 sandwitch in a new box, together with the psu, densely packed into an insulation. The on-board sensor shows aprox 35C and the voltage dropped by aprox 6-7uV to 10.000.010V. That is somehow in sync with my previous simple TC measurement (aprox -0.144ppm/C). I am especially happy with the nice blue glow of the VR tube inside..

[iMo]

This is the aging drift I see so far with myADR1001#1 (I will update the graph here). The output voltage dropped by aprox 1ppm (against previous measurements here) after finalizing the box, the temperature difference between the board and ambient is aprox 14.7C with the final foam isolation. The measurement starts at 9.999.999V == 0ppm. Measured against my (t)rusty HP34401A with some post-processing (gain, offset and TC adjusted, smoothed) with stock ADR temperature setting (TSET disconnected). On Jan 7th there was a 10min long power off of the box (before the measurement). The power voltage at the board is 14.345V and stable within 0.5mV so far. The temperature sensor voltage and power voltage are available at dedicated front posts as well.
PS: any new ADR1001 owners here?

[sahko123]

Looks good at this point its more or less starting to plateau. I find it interesting that some samples after peaking in there drift curve they often (but not always) return back towards the original power up.

[iMo]

With such a nice Vref in hand I've been analyzing my measurement process - I will start a new thread as I want to understand what I've been doing ..

[branadic]

It's way to early to draw any conclusions by now

1. It's only one month with just a few measurement points and some events in between.
2. Measurements were taken with a 34401A only, no comparisons (differences to other references) were taken, so what we see is probably limited by the measurement equipment.

-branadic-

[iMo]

Sure, we need more people with a better equipment involved, indeed.. Based on ADI's info on their EZone they plan to release this gadget officially in October this year.. 

[CorporateReference]

Does the EU plan to release first? Neither our sales or precision ref group contacts in US can get the ADR1001 (so they say),but did provide data sheets and info.

[sahko123]

The sampling policies may be different company to company. Chances are if the adr1k1 is released in US or EU first it would more than likely be US first. Otherwise i dont think they will release it in either first but first at the same time

[iMo]

An update..
Note:
7.1.23 powered off for 10minutes
24.1.23 powered off for 20minutes

[miro123]

Thanks for sharing the curve @ 24.01.2023 is continues - no signs of power-offs. The results of 27.01 are also very close to those of 20.01

[iMo]

An update..
Note:
7.1.23 powered off for 10minutes
24.1.23 powered off for 20minutes

[sahko123]

have you also been logging ambient temperature or only board temp?

[iMo]

Yes I do, the ambient vs board temperature difference depends on the exact position of the box in the workspace, however. The average difference is 14.72C with 0.18C stddev.
PS: the Vcc of the board dropped down by 1mV since the start of logging.

[iMo]

Any hint from people who know? How are the two ground pins REF_GND (14 and 15) wired inside the chip? Are those pins electrically equivalent? Or, are those pins wired to different internal blocks? Is there any DS recommendation how to wire them?

[RikV]

Is there any form of datsheet available yet??

[sahko123]

both ref_gnd are electrically equivalent and are connected internally. They seem to be tied nearer to there own nodes for sensing but it is not clearly stated which is which.

the datasheet isnt going to be public too soon.

[laichh]

From ADI:

pin 14 and 15 split static voltage reference ground currents. We doubled up the pins to half bondwire and lead resistance as they carry large tempcos which are of course undesirable.