### Author Topic: Lowest drift, lowest noise voltage reference (ADR1000AHZ)  (Read 81776 times)

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #150 on: October 20, 2021, 08:03:58 am »
Quote
so what I have heard now 150 deg C is the oven temperature to go? (or is it more the 125 deg C of other processes?)
In a bake & burn configuration we will also have some self heating by the biased zener.
(at room temperature this is ~10-11 deg C).

I do understand that the engineer wants a specific number for an upper temperature limit, allthough there are also some physicists among us. But noone can give you such a number.

You have to understand that the numbers given in the datasheet such as "Specified for −40 °C to +125 °C operation" or "Junction Temperature Range −65 °C to +150 °C" means continuous operation over lifetime. It's not that at 125.1 °C the part goes pop because of some curious effect kicking in, it's not as steep as that. But instead some effects are starting to accelerate, such as electromigration. Having said that, there is no reason to believe that operating the part for a week at 150 °C, either oven temperature or chip temperature, would degrade it permanently. The structures on the silicon are rather large and the burn-in time is limited to cause some serious degradation. Long story short, I wouldn't worry to much about the absolute temperature.

« Last Edit: October 20, 2021, 08:08:15 am by branadic »
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#### DavidKo

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #151 on: October 22, 2021, 12:01:25 pm »
Will not be the lifetime at higher temperatures smaller? LEDs have the lifetime only ~500h instead of ten thousands hours when the junction is at 150°C .

#### Kleinstein

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #152 on: October 22, 2021, 12:36:06 pm »
The shorter life time limit at high temperature is due to slow diffusion or similar processes to be faster with high temperature (about double every 5 to 10 C higher). With the reference we want most the those slow processes to already settle before the refrence is used. For this reason there is an initial burn in / anneal phase at a relatively high temperature to lett those effects settle in reasonable time (e.g. 1 week). Later use of the reference is at lower temperature like 40 C, just warm enough to get good temperature control.

#### rigrunner

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #153 on: October 22, 2021, 02:22:10 pm »

I decided to try something else with ADR#1. It takes about an hour to get stable with heater temperature at 150C (long legs, no baffle or insulation). With that I decided to see what happens if I power the ADR on for 60 minutes, wait 15 minutes to cool down and go again. This has given the largest shift so far. A little under 200uV upward in 31 hours.

There are a couple of data points missing or blanked out. My power controller doesn't talk to the logging part, so sometimes it screws up and powers down in the middle of a reading etc. Sorry

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#### Kleinstein

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #154 on: October 22, 2021, 03:03:57 pm »
Is the temperature regulated at the 150 C , or is it just the maximum possible to reach with the given supply ?

With regulation I would have expected much faster stabilization of the temperature. Normally it should be more like 10 seconds, maybe a minute for a stable temperature.

It may be interesting to also get a stable lower temperature (e.g. 50 C range) and maybe wait longer there to at least get a stable temperature there and get thus a comparable good reading to see changes to the chip.

#### rigrunner

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #155 on: October 22, 2021, 03:23:51 pm »
150C is regulated. I'm not using the data sheet circuit. The heater is wired up differently. At a more sensible temperature  stability is reached around 20 ish minutes.

I'm planning on dropping the temperature in a little while to see what has changed at the lower settings.
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#### Kleinstein

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #156 on: October 22, 2021, 04:39:51 pm »
Is the 20 minutes the time to reach a stable temperaure or the time to reach a stable ouput voltage ?
These 2 can be different. If still in regulation the temperature should be faster, unless most of the time at full power still before actual regulation starts.

The difference betwenn stable temperature and stable voltage can be interesting, as the extra relaxation to effect the voltage would be one of the effects (e.g. stress between case and die) to look at with the burn in process.

#### rigrunner

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #157 on: October 22, 2021, 04:59:52 pm »
Is the 20 minutes the time to reach a stable temperaure or the time to reach a stable ouput voltage ?
These 2 can be different. If still in regulation the temperature should be faster, unless most of the time at full power still before actual regulation starts.

Good point.
20 minutes is the time to reach stable output voltage.

The difference betwenn stable temperature and stable voltage can be interesting, as the extra relaxation to effect the voltage would be one of the effects (e.g. stress between case and die) to look at with the burn in process.

When I lower the heater temperature next I will hook up another DMM for the heater opamp and log a sample to show the heater settle time.
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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #158 on: October 24, 2021, 09:48:23 am »
Here is an update of my drift measurement, almost 2000 h have past. Again, the reference wasn't pre-aged, only the z.t.c. temperature was measured, the oven adjusted to that temperature, the amplification adjusted to 10.000 00 V and the overall t.c. trimmed. The reference is sitting at the bench, supplied by a low noise lab power supply.
The reference is drifting downwards compared to F7000-1. By the eye the drift is not linear, but slightly curved, a sqr-fit matches best. Although, we are looking at 3.2 ppm of change, which is quite a lot. I'm tempted to stop it here and to perform a one week cooking, using the internal oven. On the other hand I could also build a second one. Not yet sure how to proceed.
Don't take the result too serious, this is only a single specimen and thus without any statistical significance.

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#### Kleinstein

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #159 on: October 24, 2021, 10:21:35 am »
The drift still look pretty linear. There is a little curvature in the curve, but not really much.  Chances are, that just longer waiting would not change very much (excepts the continued linear drift).

Going up in tremperature for some time would be an option. Similar some time (e.g. 1-2 days) of power off may also be an option, to see if there is a hysteresis from power down.  The change to a higher temperature may need to power down anyway. So if possible, one could to the change in the configuration in a way so that one could do 1 day power off, than maybe 1 day with the current temperature (to see if there is a fast settling part) and only than cooking at a higher temperature (with the internal heater likely more 100-120 C). It could help to also get readings at the higher temperature - so keep the regulator active and just change the set point and maybe increase the external temperature for the whole board a little.

To see the change it would be good to get back to the current temperature / config anyway.

#### Andreas

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #160 on: October 24, 2021, 03:51:40 pm »
Here is an update of my drift measurement

It would be interesting also to have the 6.6V output data.
So we do not know wether it is the zener or the output voltage divider.

with best regards

Andreas

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #161 on: October 24, 2021, 04:42:24 pm »
As the same output stage was used on several other LTZ references before, without showing any drift, I'm convienced, that it's the ADR itself
However, equipment is limited, so you can't track it all at the same time.

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#### miro123

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #162 on: October 24, 2021, 05:13:13 pm »
The graph is almost linear
If I characterize reference I'd measure the reference. Re-start and mesayre for 1 week wil have you and idea if the trend is changed

#### wutieru

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #163 on: October 25, 2021, 12:29:26 am »
Noise testing，it seems that in right way.

#### ScoobyDoo

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #164 on: October 25, 2021, 07:19:52 pm »
Hello Voltnuts,

I received following communication from the ADI product marketing team in USA responsible for the ADR1000 release - In a nutshell they made following communication:

The ADR1000 will become available through various sales channels (Digikey - Mouser - Arrow) and an EV-board is in progress - but due to other related product releases (ADR100x) - with higher priority - this process is rolling out more slowly than anticipated - some patience is needed before this part will be available through your preferred distributor sales channel ...
The fact that Digikey and Mouser were mentioned means that for Voltnuts it will be much easier to order these parts in smaller quantitities & w/o VAT reg. hurdles

The ADI product marketing team is hoping to ‘release’ this part on the web by end of year.

Best regards
ScoobyDoo
« Last Edit: October 25, 2021, 07:55:22 pm by ScoobyDoo »

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#### rigrunner

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #165 on: October 27, 2021, 04:52:38 am »
Is the 20 minutes the time to reach a stable temperaure or the time to reach a stable ouput voltage ?

Thanks for making me take a closer look at the heater settle time.
The heater was making it to around the 85-90C mark pretty quickly and then taking the rest of the cycle to slowly reach 150C. My 11V on board supply was the problem. Running with a higher supply the heater settles much faster now.

« Last Edit: October 27, 2021, 05:12:28 am by rigrunner »
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#### Andreas

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #166 on: November 02, 2021, 07:34:58 pm »
So according to that what is published the burn in cirquit would look something like this.

Hello,

after the discussion I plan to do a  up to 125 deg C burn in cirquit.
So I can use standard PCBs (non high TG) and standard (non PTFE) burn in sockets.

Some impressions of the mechanics with security switchoff at 140 deg C.

With best regards

Andreas

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#### Andreas

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #167 on: November 13, 2021, 06:24:50 pm »
Hello,

I am trying two different methods of finding the Zero TC point of the ADR reference.

method a)
via setpoint change (using a external DAC to influence the voltage divider for the setpoint) and active internal heater
in this case I can do rather fast temperature sweeps (1K per minute shown) which saves measurement time.

method b)
via external (environment) temperature change in this case the internal heater is de-activated.

In both cases the temperature sensing transistor (Pin 6 + 8 ) connected together is used as X-axis = internal sensor temperature voltage for the diagram.
The y axis is the zener voltage over temperature.

in case a) (heater on) I get 542.4 mV = 47.5 deg C as zero TC temperature
in case b) (heater off) I get 538.2 mV = 49.4 deg C as zero TC temperature

so around 4 mV temperature sensing voltage difference or 2 deg C which I cannot explain

with best regards

Andreas
« Last Edit: November 13, 2021, 06:29:08 pm by Andreas »

#### Kleinstein

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #168 on: November 13, 2021, 07:00:05 pm »
The test with the environmental temperature also effects the resistors. So the resistor TC would be included. I have not calculated how much shift ( added linear TC) is needed, but it may not be much.  Another part is possible thermal EMF, that may come in from the heater power. This may cause a little and would be part of the residual TC even if the heater is active.

There is a small contribution from the base current, but this should be only some 0.2 mV of shift.

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#### dietert1

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #169 on: November 13, 2021, 08:37:49 pm »
Also reference voltage at zero TC point shifted by about 18  uV (3 ppm).
If you calculate the residual TC at the average temperature 48.5 °C, i'd guess it will be very small and much better than a LTZ 1000. I mean if you can't decide which oven method you will use.
Our LTFLU references run in small TEC ovens with the support circuit, including the 10 V amplifier. I know they run better when using a mixture of on-chip temperature measurement and oven temperature measurement, since the circuitry around the reference chip imposes its TC times small temperature differences (gradients inside oven). These effects can be separated by their response times. After a temperature step from another temperature to your zero TC point you may see a response with a fast and a slow component that finally compensate each other in steady state.

Regards, Dieter

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#### Andreas

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #170 on: November 14, 2021, 08:20:18 pm »
Hello,

still waiting for some parts for the burn in PCB.
But in the mean time I did some dry-runs with the little oven within the coffee mug.

All tests with ~15V supply voltage (unstabilized).
So with the two 10 Ohms resistors in series I have around 11 W heater power.
The heater is isolated with some cotton cloth.
At 130 deg C inside the outside of the coffee mug is around hand warm.

Startup time from 25 deg C to 110 deg C is less than 25 minutes.
There is enough heater power to do ramps with 2 deg/minute between 110 and 130 deg C.
So this will be also the possible burn in cycle which takes 2 hours. 10 minutes ramp and 50 minutes steady state.

Switch-off of overtemperature switch is done at ~137 deg C. ( Data sheet value = 140 deg C +/- 5 deg C).
But in this case we have a large hysteresis down to 115 deg C until the switch closes again.
Eventually a ramp between 115 and 135 deg is possible without interference of the overtemperature switch.

with best regards

Andreas

#### RikV

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #171 on: November 21, 2021, 03:20:44 pm »
As of today, 21st of november, the ADR1000 nor ADR1001 are listed on the AD website (https://www.analog.com/en/products) (in Belgium), nor on the ADX site. Mouser.BE doesn't know the device (even not the ADR1399). So, what is all this?

#### Andreas

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #172 on: November 21, 2021, 09:31:52 pm »
Hello,

I am using long legs.

And the output voltage (10V) is done by a 2:1 statistical output voltage divider (nominal ratio = 1.500000)
Zero TC of the zener is relative low with ~49.5 deg C.

Calculated setpoint temperature is ~51.8 deg C (so slightly above Zero T.C.)

Result:
10V output voltage T.C. ~190 ppb/K.
6.6 -> 10V transfer ratio ~24 ppb/K and ~6 ppm too low against nominal ratio.
(so naked zener would be 166 ppb/K).

Did someone already check the influence of the length of the legs on T.C.?

with best regards

Andreas

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#### Andreas

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #173 on: November 22, 2021, 08:08:13 pm »
Hello,

another test.

the idea was: can I influence the slope of the T.C. by using a slightly higher (or lower) setpoint temperature as the Zero T.C. temperature.
Above the zero T.C. temperature the slope is falling so what when setting the setpoint somewhat higer (or lower?)
I adjusted the voltage divider for T.C. setpoint from 11.5 / 1 to values in 5 degree steps.

With ~10-12 deg C self heating of the device by zener current I expected to see the device falling out of regulation when decreasing the setpoint to 46.9 deg C.
Interestingly was that this was not the case. (obviously the zero T.C. is good enough to compensate this for environment temperatures up to 40 deg C.)

I made a further test  with 41.9 deg C which clearly showed that the temperature regulation is only valid up to ~32 deg C.
Result: I need to set the zero T.C. and the final oven temperature somewhat higher (e.g. 52-55 deg C) for a environment temperature up to 40 deg C.

Total result: unfortunately the slope of 190 ppb/K cannot be compensated by setting the heater setpoint slightly around the zero T.C. point.
(although the graphical representation seems to have a sweet spot near the zero T.C. temperature, but maybe this is only stray by the measurement uncertainity).

with best regards

Andreas

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#### Kleinstein

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##### Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #174 on: November 22, 2021, 09:06:53 pm »
The small residual TC for the ouput valtage can be from multiple sources.  The TC of the unheated reference and than a not so perfect temperature regulation is only one possible mechanism. As it looks this is more like a small part.

Other contributions are the resistors (though better than with the LTZ1000 as much less effect from the temperature setpoint). There is still the 100/120 Ohms resistor to set the current and the collector resistor(s).

Anther contribution is directly an effect of the temperature gradients on the chip or at the case and thus the heater power. One could check this part by adding / removing some insulation around the chip. The constant part of the gradients are not a problem, but the heater power changes about linear with the external temperature and temperature gradients about scale with the heater power. So the temperature gradients will change about linear with temperature.

Ideally one would get a stable temperature of the reference without much change in the heater power - like having a 2nd oven, even if not very stable.

The board temperature can also change the mechanical stress to the reference, though I don't think this would be a large contribution - at least we should hope it is not, as thus would also come with a humidity effect.

Smf