Author Topic: ADR1001 - Ovenized Voltage Reference System  (Read 159638 times)

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Offline magic

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #425 on: December 27, 2024, 05:58:27 pm »
But I fear for accurate readings of temperature a pull up resistor will not be sufficient.
IIRC the change in forward voltage from 1°C difference is equivalent to 7% change in bias current.
 

Online iMoTopic starter

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #426 on: December 27, 2024, 06:04:04 pm »
What is interesting - the LTspice model outputs temperature in degreesC (at least it did - see the TSET sims in this thread).

PS: a 50-100uA current source may help..
« Last Edit: December 29, 2024, 11:04:04 am by iMo »
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Offline Andreas

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #427 on: December 29, 2024, 10:00:54 am »
PS: a 50-100uA current source may help..
Hello,

shure, but since they are connected to reference ground: how much will the additional current across the bond wires/PCB traces affect the output voltage?
Is it ~ 100 mOhm * 0.1 mA = 10 uV or more?

The remote sensing ICs normally have at least 2 different current levels to increase accuracy to 0.5 .. 1 deg C without calibrating the sensor.

with best regards
 

Online iMoTopic starter

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #428 on: December 29, 2024, 10:31:43 am »
The current source should be stable and then the additional voltage drop on the traces will be constant too (my above sim shows it).. With a simple resistor there in sensor's collector the drop will vary based on the temperature..
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Offline Kleinstein

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #429 on: December 29, 2024, 10:52:01 am »
The 2 current levels would only be needed to get an absolute value. Alternatively one could use only the temerature sensor with a cold chip to get a starting point. Just looking at changes in the temperature, e.g. to compensate a TC in unheated mode could use a constant current. Chances are one could use less, like 10 µA and still have good enough a temperature signal.
 

Offline magic

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #430 on: December 29, 2024, 11:13:06 am »
As far as I see there is no GND force/sense, all reference ground current flows through one fat trace to the two REF_GND pins.

Thermal diode current also joins this path at one point so extra voltage drop is inevitable, but not sure if you need much current there? Wouldn't 1MΩ to REF6P6 do the job?

Also, note that this trace already conducts a substantial reference transistor current, which is not stable with temperature (proportional to zener voltage). A resistor from TCHIP to REF6P6 would simply increase this current by a small fraction.
 

Online iMoTopic starter

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #431 on: December 29, 2024, 11:19:15 am »
Simplest variant ala magic..
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Offline kerwenard

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #432 on: January 10, 2025, 07:50:44 am »
https://www.analog.com/en/resources/app-notes/an-82f.html

[Non-English text removed by Moderator]
« Last Edit: January 19, 2025, 01:48:15 am by Halcyon »
 
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Offline jaromir

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #433 on: January 17, 2025, 11:33:18 pm »
One cold winter day I received a message informing me that a package is underway and I should expect it in no time. Indeed, a guard in blue, red, orange and yellow striped uniform appeared and handed me an urgent package containing a powered ADR1001 reference, built by Imo, a valued member of this community.
Since I had only a few days before he returned to pick up this valuable cargo, I started a quick evaluation of this reference.

1, At first I went for noise measurement. My setup consisted of DUT, connected to LFLNA-80 preamplifier, followed by HP34401A triggered by Rigol DG822 function generator to obtain a 25Hz sample rate.
Three measurements were performed, with various DUTs - a 50R termination resistor (logged as 25SPS_n-50r.csv), then ADR1000 containing ADRMU reference from Marco Reps (logged as 25SPS_adrmu.csv) and finally, reference from Imo (25SPS_im.csv filename).
Python script was used to generate a NSD chart attached below (see 1_NSD_result.png). It is obvious that ADR1001 in this circuit (utilizing its internal scaling resistor and amplifier) does exhibit higher noise than ADR1000 with scaling resistors and an amplifier, especially at lower frequencies.

2, Then I connected the reference to Datron1281 DMM and logged voltage overnight. I measured ADR1000 based reference under similar conditions. Measured values were visualized in a chart, and for both logged charts I added a 20 point long moving average to point out the low frequency noise somehow better, see 2_6h_log.png
This measurement confirmed previous findings - ADR1001 in this circuit seems more temperamental than the ADR1000 reference.

3, Last test I performed was a rough temperature coefficient test. I left the reference enclosure thermally insulated and the loss heat from its PSU did the rest. Over the course of a few hours internal temperature slowly rose by 6 degrees Celsius from healthy 37,5 to over 43 degrees. HP34401 logged the voltage from an LM35 sensor near the ADR1001 IC, built into the reference circuit by Imo. Logging this data and the reference voltage provided me with an indication of the reference temperature coefficient. See the picture 3_tempco.png
The result is relatively noisy and it's difficult to put a good trend line over the data, but it seems like the sensitivity is a bit below 1uV per degree Celsius in this narrow temperature range (though probably wide enough for lab use).

At this point I had to return the reference box to its author. Results of the processed data are below, as well as source data in case anyone wants to play along.
 
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Offline aronake

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #434 on: January 18, 2025, 06:26:45 am »
Anyone have any kicad or other pcb design software files to share from some ADR1001 project?
 

Online iMoTopic starter

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #435 on: January 18, 2025, 10:03:57 am »
I would only add to Jaromir's info above (Thanks!) - that myADR1001#1 reference was switched off from July 2024 to mid December 2024 (aprox 5.5 months), and switched on 2 weeks prior to the delivery to Jaromir's Labs.

My 34401A showed 9.999.890 at 23C couple of days back, and now both are switched off again.

Also I am missing the 100nF capacitor in the feedback of the ADR1001's internal output buffer, as it is indicated in the DS for 10V out (well, I built it 18 months before we got the first official DS handy  :D )..

Hopefully we will see more projects with that reference here soon..  :-+
« Last Edit: January 18, 2025, 11:44:40 am by iMo »
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Online iMoTopic starter

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Re: ADR1001 - Ovenized Voltage Reference System
« Reply #436 on: January 21, 2025, 08:56:30 am »
FYI - you may enjoy new pcb renderings of TiN's ADR1001/REF80 compatible boards

https://xdevs.com/article/ref_ex/
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