EEVblog Electronics Community Forum
Electronics => Metrology => Topic started by: vmiguel on August 05, 2021, 07:30:17 pm
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Voltnuts Rejoice!
If you got you got, if not is too late :)
;D
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:-//
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Pray, what is this ADR1000 of which you speak?
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Feel free to share the datasheet here
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I swear he had posted it, then deleted it.
Here you go:
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Does anyone have samples yet?
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if the ADA4084 opamp negative power connection is grounded, it is not the best device to use with this voltage reference, When the common mode input voltage is between 0 and 0.5V the Bias current can suddenly change 200na. The offset voltage has a step change also. These effects are reduce by the gain of the internal transistors but there is no need for that instability in a precision circuit.
The new voltage ref looks great!
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Does anyone have samples yet?
We have already seen first result on it :)
https://www.eevblog.com/forum/metrology/lowest-drift-lowest-noise-voltage-reference/ (https://www.eevblog.com/forum/metrology/lowest-drift-lowest-noise-voltage-reference/)
-branadic-
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The suggested ADA4084 is a nice OP, but likely not the best choice for the suggsted circuit. I have not found data for the low frequency current noise, but it could be a problem. The OPs see a rather high source impedance (some 60 K) and current noise thus matters.
The OP is not that critical, so that the difference may not be that obvious.
Chances are the classic LT1013 like in the standard LTZ1000 circuit would be the better choice.
6.6 V ouput voltage mean scaling to 10 V would be a factor very close to 1.5, which could be nice.
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All right, a few notes:
Nice to see tempco susceptibility in the datasheet, that was something I almost had to guess from the LTZ1000's. They even put thermocouple effects in it, once again, this is great.
The circuit is very similar to the LTZ1000. The end result is lower noise on paper, but the peak to peak noise is almost unchanged. The 0.2ppm tempco seems worse, but I dont think it really is in practical applications. They probably built their circuit without those hermetically sealed VPG foil resistors, as most users will.
ADA4084: Probably a sales decision to put a twice as expensive opampm there, without a TI alternative. I dont blame the engineer.
6.6 V ouput voltage mean scaling to 10 V would be a factor very close to 1.5, which could be nice.
I was just thinking of that. Scaling 7.2V is odd, we either do PWM, or live with the issues of resistor scaling. Scaling 6.6V to 10, we can use the LT5400B and a trimmer, which is a lot cheaper than those bulk metal foil resistors with similar performance.
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What a sad day! :palm:
Needs 10mA more than LTZ1000A for the same setting.
And we still have those Kovar leads.
But great day for those who stocked old chips. I regret not having bought if 100 units when they were < $46.06.
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Although it could be useful for a 0.48V reference (Dual LTZ1000A - ADR1000).
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The curve for the supply current is with a lower temperaure set point for the LTZ1000. Chances are this is just one example and the heater resitor on the LTZ1000 had quite loose specs. So the actual current needed for the LTZ1000A could scatter a lot, though many more can be more in the middle. At least the new heater specs are relatively tight - so the needed current is more predictable.
The noise is slightly lower - though this maybe more the higher frequency noise - not clear how the very low frequency noise behaves. There is quite some scattering anyway ! For some reason they show the noise curves with the heater inactive - so this may include thermal fluctuations.
The big plus is a lower TC before temperature control and thus less demand on the resistors. So the drift and TC contribution from the resistors is reduced by about a factor of 2.
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Thanks Vgkid :)
There were rumors about a ADR1000-Version with integrated resistors and OPs, is that bollocks?
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Looks like Keysight can update the 3458A A9 Vref module now and offer a 1ppm / year factory option!
Two sealed Vishay BMF resistors could raise the voltage 10% to match the LTZ1000 voltage with no impact on drift.
With this lower Vref noise the old LT1001 (10nV / rt Hz) amplifiers on the ADC A3 PCB could need updating. I know some good choppers they could use.
The noise at the fundamental ADC frequency of 6Hz is now 1/2 of the old value. So that should help it's operation.
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For a direct replacement of an old LTZ1000 reference the 7-8% lower voltage may be an issue. Using resistors for gain would still add to the drift, more than the resistors at the reference directly.
The drift specs are not that much different from the LTZ1000. The total circuit drift also include some contributions from the resistors - though less with the new ADR ref. Another point is that the typical value in the data-sheet are not yet that well tested. The DMM spec. numbers for the drift should also include hysteresis effects and an extra K factor of some 2 to 3 to get from typical values to expected upper limits. The logical 1st setp to better drift specs would be s slightly lower set temperature at the cost of lower maximum environmental temperature.
Adaption to the lower reference voltage at the 3458 could be done at the ADC: replace the 7 to 12 V part included in U180 with 2 external resistors. The 2 resistors here don't have to be matched to the other resistors inside U180.
The LT1001 OPs in the 3458 ADC are only a small part of the ADC noise and drift. For 10 PLC mode the relevant frequency would not be 6 Hz, but 3 Hz (or 2.5 Hz with 50 Hz mains) - there are a few possible modern alternatives, even without using choppers.
For some reason the ADR1000 is not found easily on the analog website. So there may be a problem or delay and maybe still some change.
The external OP is the least problem - an LT1013 is not that expensive and large. The weak point is the need for the external resistors (e.g. 70K, 70K, 100 Ohms, 1 K, 13 K). The caps would be very hard to integrate on a chip.
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It wouldnt all fit in a TO99-package, but maybe in a TO3-package like the Apex PA88 https://www.richis-lab.de/images/Opamp/03x02.jpg (https://www.richis-lab.de/images/Opamp/03x02.jpg) :popcorn:
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For many used with a relatively large temperature range the reference would run reasonable warm (like 60 C or even more). OP performance is better at low temperature.
With more parts that need power the oven would also need more power. As a rule of thumb I consider oven power to be about 2 times the power of the circuit inside at least. So ideally only the parts that need the oven and are low power should be kept at temperature - other parts are better outside.
A smaller circuit also makes the oven faster and this helps to keep the capacitor reasonable small without going too high in impedance.
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For some reason the ADR1000 is not found easily on the analog website. So there may be a problem or delay and maybe still some change.
Couldn't find it at all on the website, did something change or am I not looking hard enough?
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Couldn't find it at all on the website, did something change or am I not looking hard enough?
Hello folks,
The part is released but ADI will not take it to the web - something ADI rarely does.
Best regards
ScoobyDoo
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Couldn't find it at all on the website, did something change or am I not looking hard enough?
Hello folks,
The part is released but ADI will not take it to the web - something ADI rarely does.
Best regards
ScoobyDoo
Interesting, will it only be available for "selected" customers?
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Interesting, will it only be available for "selected" customers?
The ADR1000 is intended for selected customers
The ADR1001 will probably be put online and made available through distributor channels.
The ADR1001 contains all necessary resistors and HW implementation is rather easy
Best regards
ScoobyDoo
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The ADR1000 is intended for selected customers
That's confusing. Any idea why?
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Hello folks - the people from ADI did not divulge a rationale and so any word on this would only be pure speculation ...
However the good news is that most likely the ADR1000 IC team lead will give an online presentation during MM2021 ...
So you all have a good reason to attend MM2021 (Stuttgart) - ( if CoVid rules allow us ... )
Best regards
ScoobyDoo
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Damn, now you've leaked the secret surprise talk that I could organize thanks to the help of my german ADI contact! |O
-branadic-
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They say on the datasheet about a "15°C of margin". So the maximum ambient temperature would be 60°C. And at that point the LTZ1000A needs just 8mA and the ADR1000 requires 22mA. That is not an improvement at all.
At normal room ambient temperatures (10C to 30C) the LTZ1000A will need less than 10 mA than the ADR1000. It doesn't make any sense that you claim in the datasheet that "The ADR1000 uses a specialized epoxy die attachment to maximize the thermal isolation that reduces the power consumption required to achieve a given set temperature." but you cant beat the LTZ1000A.
They also say "At an ambient temperature of 10°C, the heater power consumption is approximately 35 mA2 × 242 Ω = 300 mW".
I wonder if they made a mistake and they swapped the LTZ1000A and ADR1000 curves.
I need to ask, there is nothing better in 2021 for hermetic sealing than those KOVAR leads?
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They also said:
"Increasing the current in the Zener (IBZ1) reduces the reference noise by the inverse square root of Zener current. Zener bias current above 8mA is not very practical as power dissipation limits maximum ambient temperature."
They probably made a mistake and the graphs are swapped.
(I guess that the curve for ADR1000 is the lower one, and that explains why they recommends 15C margin, 60C is the maximum ambient temperature allowed to regulate to a Tset of 75C. But then you are maybe right to say that the ADR1000LTZ1000A just needs 5C margin. (Jesus, I can foresee now hordes of people stocking LTZ1000A chips!)
If that is the case, then they also probably wanted to mean "At an ambient temperature of -10°C, the heater power consumption is approximately 35 mA.")
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The ADR1000 is intended for selected customers
That's confusing. Any idea why?
Then, It's really a sad :( sad :( sad :( day. No (paid) samples option for us either?
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Damn, now you've leaked the secret surprise talk that I could organize thanks to the help of my german ADI contact! |O
-branadic-
But I think it better now because we can prepare many questions in advance. Someone might be probably listening, so here it goes.
Question #1: What was the reason (or reasons) why ADI started this new design?
A) some LTZ1000 source materials were no longer available.
B) the foundry in which the LTZ1000 were done was going to close that process (or the whole foundry was to close).
C) the main paying customers didn't liked anybody to be able to source this component. So they asked ADI for LTZ1000 discontinuation an paid money to create a new reference just only for them (and maybe a less performing second IC alternative for ordinary people).
D) after 30 years, the original designers have described many possible improvements and they were allowed to do more R&D on this IC without any budget limit to create the new best top performing voltage reference in the world.
E) after merging the management team was able to laid off all those old bearded engineers, and they assigned this task to the new young employees to have them something to distract with.
F) we have no idea, management just tell us one day that we need to read the (more that one houndred pages) eevblog LTZ1000 thread, and to propose some design change with two requirements: 1) removal of 'LT' initials from the LTZ1000 and related components (LT1013); 2) keep that kovar leads and packaging because we don't have any need, money and time to mess with that problem.
G) Other reasons : (tell us, please ..........................)
Question #2: Why still those KOVAR leads?
A) No cost/performance technical alternatives.
B) We didn't have any budget to do RD on this item.
C) Management/Customers didn't wanted/allowed us to do any modification.
D) Other reasons : (tell us, please ..........................)
Question #3: Why no stated noise graphs at oven temperature?
A) Because they were awful. Please, don't tell anyone.
B) Because we didn't have time or resources. And probably will never have.
C) Other reasons : (tell us, please ..........................)
Question #4: Why only data for Tset = 75C?
A) Because this is the most stable Tset temperature.
B) Because we didn't have resources to do additional testing. Also the main (paying) customer wanted this temperature, so we will not test any other temperatures.
C) Other reasons : (tell us, please ..........................)
Question #5: Has the pop corn noise been investigated, measured, solved?
A) Pop corn noise? What is that?
I have no idea what are you talking about. Please, next question.
Question #6: EMI/RF issues.
There have been discussion about need or not for additional capacitors on the PCB to strength the EMI/RF issues of the reference.
Also there have been claims that there is a need for thick cold rolled steel enclosure (1.6mm, or even better 3mm) to keem EMI/RF issues under control.
Has any testing been done about this?
A) uh! That is your problem. We are just IC designers, we don't care about anything far away than those kovar leads. Also why bother?, our customers have been 30 years handling this issue, and they still buy our chips.
B) That would take a lot of time and will cost a lot of money. Do it yourself.
C) I will tell you a secret, but please don't say anyone. Let me tell you a story about the 'Crystal Lattice' ... (Edwin, Digilentminds we really miss you!)
D) Other reasons : (tell us, please ..........................)
Question #7: Did SMD, hybrid or ceramic packaging crossed your minds?
A) Why? We are lazy. And who is going to pay that? Common FR4 PCB has been used for more than 30 years.
B) We dreamed about that and even talked a few times during launch, in that PCB layout only 4 or 5 components need tightly thermal stability so it would make sense to have ADR1000, R1, R4, R5 on a smaller (cheaper) Aluminium oxide or AlN ceramic board as inner-most oven to keep constant temperature and prevent issues with those Kovar leads. And all other components on normal FR4 PCB ... but Management/Customers didn't wanted/allowed us to do any modification.
...
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For the current consumption, much of the difference between the 2 curves is from a different set temperature. The one with the higher consumption runs hotter and also seems to work to a correspondingly higher temperature. So to compare one should shift one curve by some 12 K (the difference is max working temperature). These look like curves for just 2 units. The heater resistance in the LTZ1000 has quite some tolerance (200-420 Ohms) and the needed heater current scales like 1/sqrt(R_heater). So it could be just a different heater resistance.
The ADR10000 has a heater resistance spec. quite a bit narrower and more to the lower end of the values. So it is normal to expect a little more current, but also less scattering and the worst case current (lowest resistance) is lower.
The difference to the LTZ1000 is quite small - not really a new design. It could be as little as a slightly different doping level to get the lower voltage and naturally a shift in the Zener TC (which results in the reduced unheated TC). Slightly less noise at a lower voltage is also not such a surprise. In the extremes this could be just a batch that got a bit off center and ended up with slightly different properties.
Chances are they could offer the LTZ1000A and ADR1000 in parallel - some meters are designed for the higher voltage. It should not be so hard to produce bother versions.
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The ADR1000 and LTZ1000(A) will co-exist on the market - but the ADR1000 is for sure the better part and there is more to come - certain things (roadmap, ... ) are still under NDA ...
Feel free to list technical (related) questions in this post - so ADI team can answer (technical) questions during MM2021 event.
Stay tuned ... welcome to MM2021 summit.
Best regards
ScoobyDoo
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For the current consumption, much of the difference between the 2 curves is from a different set temperature.
They don't say that:
"Figure 6. Total Supply Current vs. Ambient Temperature, TSET = 75°C"
Nowhere in the datasheet they say that the graphs are for different TSET point.
And why on earth would they (or we) want a comparison graph with different temperarure settings?
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The 2 power curves show quite a difference in the temperature where the current goes down to a low value when the heater turn off. This is at some 62 C for the lower power one and some 74 C for the higher power one. The useful maxium ambient would be something like 10-15 K lower. So even if the nominal set temperature after some tables may be 75 C. The actual values are obviously different.
The current consumption also depends on the rest of the circuit. The AD4084 is a little more power hungry than the LT1013. The position of the transistor for heater control can also have an effect. If close to the reference the power from the transitor can contribute - if done right this may even help with the overall TC.
With a higher resistance for the heater, the LTZ1000 would need a higher supply voltage for the heater, though tyically less current. The rather large range for the LTZ1000 heater resistor requires a relatively high voltage (in case the resistance is high) and a high current capability (in case the resistor is at the low end).
One could argue a little that a precision application would likely have a 15 V or similar supply anyway. So a little higher resistance may have been better, but the tighter tolerance definitely helps.
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I kind of get why they kept Kovar leads. It's not just budget for exploring alternatives. It's time. My understanding is that there are no alternatives that had the same amount of testing in the field. We talking tens of years (untold thousands if combined) of thermal cycling and whatnots.
If thermocoupling is a significant problem for a particular design - why not simply install a thermal short between pins 3 and 7? Like one of those thermawicks from Vishay?
Same for R1 and R4/R5 (if not array'd)
Funny thing about those - when manually soldering touching one end with soldering iron - other end melts too. :-DD
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[..]
But great day for those who stocked old chips. I regret not having bought if 100 units when they were < $46.06.
Is here someone who did? I'm still short of a LTZ1000 for my reference (got the resistor set and somewhere one of Brandic's boards). I gladly buy one of those now obsolete chips from you. :D
But back on topic, me too would like to see a multi-function integrated solution like the AD687. The ones in CERDIP performed quite well.
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We need a die shot!!
:D
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We need a die shot!!
:D
This would probably not be much different from the LTZ1000 die. It could be as little as slightly different doping levels and still the same masks as with the LTZ1000.
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Probably they couldn't resist changing at least the metal and buried layer near the heater pads ;)
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We will probably hear about history of ADR1000 at MM2021, but rumor says developement started long before ADI aquired LT. So we can expect some difference I guess.
-branadic-
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Hello,
I hope they did not change too much on the imho optimized design.
Otherwise we could get some drift by tilting the device similar to the LM399 chip.
with best regards
Andreas
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One problem with the LM399 is the loose thermal cover. I think its movements may be the reason both for popcorn noise and positional dependence. One mechanism may be a minute temperature change, but i can't tell any numbers like the LM399 TC at its operating temperature. Anyway, i am operating 15 LM399 right now, all with fixed thermal covers and no popcorn noise observed. Last week i turned around a board with 10x LM399 to mount it "heads down" because i want whatever "dirt" may be inside to stay away from the silicon.
Sooner or later noopy will get an ADR1000 and show us the die to put an end to speculation. My guess would be: Four zeners => half the noise.
Regards, Dieter
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How sensitive is the LM399 to orientation? I think it could be not as much a matter of absolute temperature as thermal gradients. Quite obviously, each 1mK mismatch between the zener and its compensation transistor is guaranteed 2µV change in output voltage. Extrapolating to a linear gradient across the whole device, it would be perhaps 10mK across the die and, dunno, maybe hundreds of mK across the can - hard to tell due to different shape and less conductive material. Not sure if airflow or the thermal cover could cause that, but if they can then your answer may be here...
LTZ places critical components concentrically in the dead center of the die. Everything in it is concentric, actually.
My guess: AD logo, ditched the unused inner heaters to make space for the rumored ADR1001 scaling resistors, maybe increased diode diameter if you insist on that. And all else invisible.
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How sensitive is the LM399 to orientation?
Some results are here:
https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg360779/#msg360779 (https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg360779/#msg360779)
It mainly depends on (additional) thermal isolation of the LM399. And of course of the individual reference itself.
with best regards
Andreas
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Interesting, the effect is quite clear. But the cause must be something else than I thought, because polarity of change is opposite to what was expected. Nevertheless, the worst cases 1/3 correspond to the die being oriented "sideways", with the heater on the left/right respectively (top view). :-//
edit
Unless there is some reason why the top-facing side of the can is cooler than the lower side.
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The 399 chip is of highly asymmetric design - and the gas molecules still have a lot of space inside its package to change their flows around the die.. Unless the phonons in the die lattice are affected by the gravity too.. :D
PS: also the bonding wires could create a different force at the die based on their orientation in the gravity field. With an asymmetric design it may play a role. Like with crystals - while changing orientation of an ocxo (for example) you may easily see a frequency change..
Edit: added "chip" after "399"
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Every reference containing an integrated heater is somewhat sensitive to tilting. The principle is also used in thermal inclination sensors. Think of a candle, that likes to straighten its flame upwards. Even if the buried zener is surrounded by the heater there will be a small change in temperature. Having the zener adjusted to z.t.c. will however surpress the effect.
-branadic-
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The 399 is of highly asymmetric design [...]
I always assumed that the majority of the orientation sensitivity was the insulating plastic-cap shifting around ?
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The 399 is of highly asymmetric design [...]
I always assumed that the majority of the orientation sensitivity was the insulating plastic-cap shifting around ?
"The 399 [meaning the components on the chip/die] is of highly asymmetric design.."
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If the plastic cover is loose and rests only on the upward-facing side of the can then it may cool that side and produce a thermal gradient across the package and the die inside. My theory of thermal mistracking between Q3 and Q13 actually works in such case.
Zero TC helps if the temperature regulation transistor is at a different temperature than the reference.
Nothing can save you if the diode and transistor which constitute the reference itself are at different temperatures from each other. That's where all the non-LTZ devices cut corners to a varying degree.
Worse still, even a perfectly symmetric individual diode could be affected by gradients because areas at different temperature will operate at slightly different current densities.
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..Unless the phonons in the die lattice are affected by the gravity too.. :D
:palm:
Wikipedia:
Recent research has shown that phonons and rotons may have a non-negligible mass and be affected by gravity just as standard particles are.[19] In particular, phonons are predicted to have a kind of negative mass and negative gravity.[20] This can be explained by how phonons are known to travel faster in denser materials. Because the part of a material pointing towards a gravitational source is closer to the object, it becomes denser on that end. From this, it is predicted that phonons would deflect away as it detects the difference in densities, exhibiting the qualities of a negative gravitational field.[21] Although the effect would be too small to measure, it is possible that future equipment could lead to successful results..
The next ADR2000 revision may contain a "heat pump". The phonons could be pumped by help of an electric field into a specific direction, imho.
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"The 399 [meaning the components on the chip/die] is of highly asymmetric design.."
Yes, I know that, and provided the thermodynamic circumstances of the metal can are constant, I am sure that will cause some measurable amount of orientation sensitivity.
But they are not constant, on all the LM399's I have had my hands om, the plastic cap can move relative to the pins, and that means a huge difference in thermal conductivity between the metal can and the plastic insulation.
So by all means attempt to characterize the orientation sensitivity of the chip design, but do so only after you either glue the plastic cap to the metal can or remove it entirely.
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The movement of the plastic cap is a good point. Instead of glue I would consider a little bit of cotton wool or similar to keep it in a fixed position.
The can itself is relatively small and there is little temperature difference inside. So I don't think convection inside the case is an issue.
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Instead of glue I would consider a little bit of cotton wool or similar to keep it in a fixed position.
My preference would be to get rid of it entirely, because it does the wrong thing for what we're trying to achieve.
And yes, that is one of my pet peves: Metrology people tend to think in terms of thermal conductivity when they should focus on thermal impedance, so let me explain:
Thermal insulation = "Unwillingness to move thermal energy" = Porous low thermal capacity material which restricts the movement of gas molecules. Example materials: EPS foam, "RockWool" and knitted sweaters.
Thermal impedance = "Unwillingness to change temperature" = Solid high thermal capacity with low(-ish) thermal conductivity. Example materials: Non-crystaline rocks, bricks & concrete.
The benefit of high thermal impedance is that temperatures changes propagate very slowly through the material, around 25kg of granite will get you into microkelvin territory.
The downside is that it can therefore take weeks or months to reach that thermal equilibrium.
If you want to experiment: Sandwich your PCB between a couple of candlelight holders made from granite, concrete or mable.
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Thermal impedance = "Unwillingness to change temperature" = Solid high thermal capacity with low(-ish) thermal conductivity. Example materials: Non-crystaline rocks, bricks & concrete.
The benefit of high thermal impedance is that temperatures changes propagate very slowly through the material, around 25kg of granite will get you into microkelvin territory.
Add paraffin wax and some plastics to your list. Higher specific heat capacity than granite and lower thermal conductivity.
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So by all means attempt to characterize the orientation sensitivity of the chip design, but do so only after you either glue the plastic cap to the metal can or remove it entirely.
More like: solder thin copper twisted pairs for zener sense, zener force and heater power (bonus: kovar cables with solderless joints). Place in the middle of a copper pipe and flood with polyurethane foam, surround with another layer of insulation. Then you may have some excuse to blame the remaining effect on air flow or dust inside the can.
Otherwise, external air and PCB are likely to have more effect.
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No PU foam inside, MgO powder. Low electrical conductivity, high thermal conductivity to avoid issues with kovar. Both Over the pcb and under the pcb too.
Once the above is done, then the thermal insulation. PU or whatever you like. Then do the tilting test again, and you now that this can only be the effect of internal die issues.
Edit: no need to say, that all of the above, without the plastic case.
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Place in the middle of a copper pipe and flood with polyurethane foam, surround with another layer of insulation.
No, no & no.
See above re: Thermal impedance
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Add paraffin wax and some plastics to your list. Higher specific heat capacity than granite and lower thermal conductivity.
Yes, there are some plastics in the right ballpark, and yes they are much easier to work, but polymers as a rule, cannot be bought in a usable shape.
You can get them as pipes, sticks, granules, sheets, foils, tapes, but not as a solid 5cm cube.
If you find something 5cm thick, it is likely to be at least 40cm on the two other dimensions, and weigh so much the postman will hate you forever.
(Cutting 5cm thick polymer takes a really good wide-toothed high-speed circular saw. Too low speed or too thin-toothed and the friction will melt the polymer and your saw will get stuck. Do not ask me how I know this :-)
All that said: Any lump of high density polymer (HDPE, ABS etc.) will give more stable temperature than what we usually see on pictures here.
But ask your wife first: There is 22% chance she have a pair of geologic candlelight holders she never uses.
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The issue with the covers is much more the prevention of thermal flow variations than pure isolation. Even a thin heat-shrink cover over the Kovar leads and package will do. Thermal air movement will create noise through low frequency temperature changes in the Kovar leads, which have about 40uV/K to copper similar to lead/tin to copper. Check low frequency performance on a LT1000 without a cover. Then test a simple heat shrink tube (no need to shrink) just cover the leads and package.
The lattice is heated and on constant high temperature. The PCB is on a lower temperature, so a thermal gradient is always present. Voltage variation equal to 1/f noise is created when the thermal gradient over the leads varies with air movement.
BR
Christian
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Hello folks
The ADR1000AHZ is now available from the ADI online webshop.
The MOQ has been set as low as 5 (one) to reach all Voltnuts - (MOQ = 5).
The part will be monitored for a period of at least six months to understand if this is a viable (sustainable) path for ADI - so pls. order as much as you can ...
ADI is checking this MPN in order to understand if ordering process goes smoothly and will remove existing issues with this MPN = ADR1000AHZ
Best regards
ScoobyDoo
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Is the AD7177-2 capable of using the ADR1000AHZ directly for its Refinput?
The maximum ratings for the AD7177-2 state:
AVDD1, AVDD2 to AVSS: −0.3 V to +6.5 V
Reference Input Voltage to AVSS: −0.3 V to AVDD1 + 0.3 V
So i would have guessed the Refinput accepts 6.8Vmax in at AVDD1 = 6.5V, suitable for a max 6.67V from a ADR1000AHZ.
Or is it foolish of me to think that might work due to substrate diodes starting to conduct/other reason?
https://www.analog.com/media/en/technical-documentation/data-sheets/AD7177-2.pdf (https://www.analog.com/media/en/technical-documentation/data-sheets/AD7177-2.pdf)
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It's not wise to run chips at their maximum ratings, nor for the inputs to exceed the supplies.
What I would do is divide down the reference to something like 6V and use that as both the supply (through a power buffer of course) and reference input.
Dividing 6.6V to 6V will attenuate the error due to the drift of the divider approximately 10 times, as discussed by Dr. Frank in the LTZ thread.
You can use a thin-film array as indicated by John Pickering and as discussed in the Statistical Arrays thread.
The recent paper by N. Beev also linked on this forum indicates the low-noise types (TDP, NOMC etc)
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These are stress ratings only, operation is not implied, blah blah...
They specify reference input range as 50mV beyond the rails, assuming you aren't using the internal buffer of course. What's beyond 50mV? Dragons... maybe OK at 25°C, maybe not.
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Thermal image of bare chip during 2 minute operation. Hottest point is die epoxy attach. Die itself looks cooler due to different emissivity and reflection parameters. Resistors for heater are 11.5kOhm/1 kOhm, zener current 4.05mA (120 Ohm).
(https://xdevs.com/doc/Analog_Devices/ADR1000/thermal_die2.png)
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They specify reference input range as 50mV beyond the rails, assuming you aren't using the internal buffer of course. What's beyond 50mV? Dragons... maybe OK at 25°C, maybe not.
In CMOS circuits you inject substrate or well currents if you go under the lowest -supply or above the +supply, unless there are special additional structures used. Typical there are diodes similar to a FET Body diode and/or. ESD structures with similar effect. So 50mV will be o.k. since you do not get significant currents. But for sensitive applications even 300mV might be to much and there are always spikes from noise etc. So do not exceed the supply boundaries on any input unless the data sheet explicit allows for that.
If in doubt, check with a nA meter at what point currents starts to flow.
BR
Christian
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Thermal image of bare chip during 2 minute operation. Hottest point is die epoxy attach. Die itself looks cooler due to different emissivity and reflection parameters. Resistors for heater are 11.5kOhm/1 kOhm, zener current 4.05mA (120 Ohm).
Is that a cut open TO package from the top or how did you make the image?
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Definitely looks like that. The orange rings are glass seals around pins and you can also see where is the pin connected to the can. The image shows thermal emissivity of the various components first and foremost ;) but temperature differences between identical materials may be comparable.
So do not exceed the supply boundaries on any input unless the data sheet explicit allows for that.
If in doubt, check with a nA meter at what point currents starts to flow.
It's worse than that, because D-S ADCs sample and hold the input in some internal capacitors which are switched by means of MOSFETs, so there is likely leakage from those capacitors too if their potential forward biases the body diodes.
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Btw, why the glass seals are 12C higher than the surrounding metal?
It looks to me like "the Blackbird vehicle faster than the tail wind" problem.. :D
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The reference has an essentially constant temperature. Nearly all the details visible is a diffenrence in the emissivity. So the picture is not eally showing temperature, but more like optical properties in the IR range, more like a normal photo, just in the IR.
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Is the AD7177-2 capable of using the ADR1000AHZ directly for its Refinput?
The maximum ratings for the AD7177-2 state:
AVDD1, AVDD2 to AVSS: −0.3 V to +6.5 V
Reference Input Voltage to AVSS: −0.3 V to AVDD1 + 0.3 V
The answer is a clear NO.
The (operating-) specs are stated for 4.5 to 5.5V. Anything outside that values is not covered by the specs.
There is an abs. voltage spec for the external reference (Vref = (Ref+) - (Ref-)) which is AVSS (min) to AVDD1 (max) with buffers enabled and AVSS-0,05V (min) to AVDD +0.05V (max) with buffers disabled.
Abs. maximum ratings only state what a chip can survive.
Cheers
Andreas
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Thermal image of bare chip during 2 minute operation. Hottest point is die epoxy attach. Die itself looks cooler due to different emissivity and reflection parameters. Resistors for heater are 11.5kOhm/1 kOhm, zener current 4.05mA (120 Ohm).
How are you deriving 4.05mA at 120Ohm?
If I plug the numbers into the formula on page 7 of the data sheet I get a slightly different figure.
11K5/1k heater should give 51.265 C die temperature.
Using the R1= 0.658V-0.0022*51.265 over 4.05mA minus 7 Ohms R1 resolves to 127.62 Ohms.
To get 120 Ohms R1 with the same heater value I need 4.29mA.
I'd like to understand where I'm going wrong with the data sheet calculation :-//
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I felt like formula on page 7 slightly wrong, as there are 7 ohms in series were lost and they used 0.0022 in one spot, but 0.002 in other. :scared:
Actual heater set was 11.435/1k (13kOhm + 95kOhm in parallel), so bit different. I'd also think removed cap would affect temperature quite a bit due to no protection from air drafts/heat loss outside.
That imagery is more of entertainment value, not metrology value.
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I felt like formula on page 7 slightly wrong, as there are 7 ohms in series were lost and they used 0.0022 in one spot, but 0.002 in other. :scared:
The example in the data sheet is also wrong in that it doesn't appear to subtract the 7 Ohms. The 129.5 Ohm example result should be 119 Ohm (using the .0022)
Actual heater set was 11.435/1k (13kOhm + 95kOhm in parallel), so bit different. I'd also think removed cap would affect temperature quite a bit due to no protection from air drafts/heat loss outside.
That imagery is more of entertainment value, not metrology value.
It's pretty :)
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The datasheet refers to a "recommended layout" on page 1 but none is given. Is there other documentation that shows this recommended layout?
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You can get them as pipes, sticks, granules, sheets, foils, tapes, but not as a solid 5cm cube.
If you find something 5cm thick, it is likely to be at least 40cm on the two other dimensions, and weigh so much the postman will hate you forever.
(Cutting 5cm thick polymer takes a really good wide-toothed high-speed circular saw. Too low speed or too thin-toothed and the friction will melt the polymer and your saw will get stuck. Do not ask me how I know this :-)
What? ???
Foam isn't that difficult to source. Here is an 8x8x8 inch^3 polyurethane cube for example:
https://www.mcmaster.com/8882K16/ (https://www.mcmaster.com/8882K16/)
As for cutting... please don't use a power saw. Instead, use something like a (hot) knife and cut manually:
https://www.youtube.com/watch?v=xne0qjhFVNY (https://www.youtube.com/watch?v=xne0qjhFVNY)
https://www.youtube.com/watch?v=E9iCz-69ibQ (https://www.youtube.com/watch?v=E9iCz-69ibQ)
:-+
Tip: If you use a hot knife (or a cheap soldering iron), do not keep it in one position too long or you might start a fire :-DD
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Foam will only give you high thermal resistance (= bad conduction), you need a solid to get high thermal impedance (= resistance to change).
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The day before Chinese National Day, I received a gift from ADI. :-DD :-DD :-DD
[img[attachimg=1]http://][/img]
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hmmm date code 2108, thats two people with the later date code
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hmmm date code 2108, thats two people with the later date code
Make that three. Got delivery today of 10 pcs w/ DC 2108.
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I swear he had posted it, then deleted it.
Here you go:
Hello all,
I just found this topic. Very interesting, also the linked datasheet is marked as "confidential", and actual it is not to find non the Analog web side.
On the 1st page of the datasheet, "Table 1. Related Products", the new ADR1399 is also not linked. In the ADR1399 datasheet there is also no link to the new ADR1000 ...
Does somebody have an idea where to get samples of the new ADR1000a?
Guido