ADR1001 - Ovenized Voltage Reference System

[dietert1]

https://wiki.analog.com/resources/eval/adr1001e-ebz

[opa627bm]

It has 2 banana for the vref sense , 5V and I think the gold SMA connector is 10V but I dont have the adaptor for it so I am running it off the front panel USB of my DMM7510 and testing it at the same time 

[branadic]

https://wiki.analog.com/resources/eval/adr1001e-ebz

Thanks, so let me repeat my statement, these connectors:



are not the proper choice for the application, neither in terms of mechanics nor in terms of t.e.m.f.. Hence I suggest to remove them and directly solder a proper cable directly to the board. I don't understand why they went away with the solution used on ADR1000 EVM



although Pomona 3770 are not perfect, but way better than the solution used here.

-branadic-

[Andreas]

so I am running it off the front panel USB

Hello,

my experience is: USB (cables), switchmode supplies (on the EVM) and uV stability do not fit well together.
I have observed up to 100uV shift due to EMI.

To check for EMI-influence try one of the following:
- touch the (isolated) cable between VREF and DMM. (one after the other and both together).
- you can also touch directly the Pins (perhaps with a thin wire to avoid thermal EMF).
- put your setup on a metal sheet (wiring close to the metal and DMM housing connected to the metal) to reduce influence.
- use battery supply (4 NiMH AA cells) instead of USB.

with best regards

Andreas

[opa627bm]

so I am running it off the front panel USB

Hello,

my experience is: USB (cables), switchmode supplies (on the EVM) and uV stability do not fit well together.
I have observed up to 100uV shift due to EMI.

To check for EMI-influence try one of the following:
- touch the (isolated) cable between VREF and DMM. (one after the other and both together).
- you can also touch directly the Pins (perhaps with a thin wire to avoid thermal EMF).
- put your setup on a metal sheet (wiring close to the metal and DMM housing connected to the metal) to reduce influence.
- use battery supply (4 NiMH AA cells) instead of USB.

with best regards

Andreas

I Ended up using the from SMA connector, with a semi ridge cable that connects directly to the DMM (suspended in mid air), the thermal EMF effect is for sure there, if I touch the outer right of the SMA connector, the output will shift up and when I release it ,it will slow decay back to normal.

[sahko123]

These eval pcbs had no effort put forward to optimise the precision and stability. They are literally for plug and play to see if the system they are attached to would even work.

There will probably be other eval boards/applications notes made for them to showcase how they can be optimised and better utilised.

the main issue with these boards is the usb power supply. The noise it injects into the outputs far out weighs the adr1001's noise. The connectors are all TEMF nightmares as well. So if you want to improve the boards remove the connectors and use an external low noise psu

[KT88]

These eval pcbs had no effort put forward to optimise the precision and stability. They are literally for plug and play to see if the system they are attached to would even work.

If you read the wiki page carefully you find this comments about the power supplay options:

"POWER SUPPLY CONSIDERATION
Use a USB-C charger or other USB-C source to power the board. You should see a Green LED. Alternately, 5V can be applied between VUSB and DGND from a bench supply. This will power the isolating LMT8048 module, providing isolated power downstream. Alternately, the downstream regulators can be back driven at VPRE/AGND (Max 20V) or at V+/AGND (Max 16V). AGND is the Reference ground, so this approach is not isolated."

This means you could see the USB connector and the isolation as an optional bonus.
Besides that the reference itself is put on a milled out island to isolate it from mechanical stress.
With a little bit of grounding and shielding pretty much every level of noise performance should be achievable if an appropriate power source is used.

One last note: An EVAL board is meant to (more or less) quickly evaluate the functionality of a part which this one clearly does, if you ask me...
If a demo circuit is meant to deliver the full performance one would call it a reference design which would in case of such a precision reference more circuitry like EMI filters, output buffers or a specific ADC / DAC...

Cheers

Andreas

[opa627bm]

Hi All,
Been having EVM for about 2 weeks now.
1. If you receive them early, with parts, some of the pin 1 marking was wrong so if you want to solder any of them better watch out for it..
2. There is 1Mohm resistor between REFGND and DGND, It is causing strange EMI problem even when I wave my hand near the board, in the end I have to bridge them and it is very stable now.
Regards,
Li

[iMo]

There is the C11=1uF capacitor directly wired against ground at the 7V-->10V/5V buffer's output, hmm..
Also the ISET resistor's value is almost complete outside the package (R8=120ohm).
And the C13=1uF is wired from the buffer's input to the ground.. Interesting.
Let us wait on what the datasheet says..

PS: below my attempt to understand the wiring - so at the 7V output there is a divider feeding a gain=1 buffer.. Is the EVM's output 5V only? [it should be..]

[sahko123]

The two ill be getting will be the same. The text printing is off by 90 degrees. With the ones you have are the pins still the rigth orientation? with the long pad being pin 1?

[opa627bm]

There is the C11=1uF capacitor directly wired against ground at the 7V-->10V/5V buffer's output, hmm..
Also the ISET resistor's value is almost complete outside the package (R8=120ohm).
And the C13=1uF is wired from the buffer's input to the ground.. Interesting.
Let us wait on what the datasheet says..

PS: below my attempt to understand the wiring - so at the 7V output there is a divider feeding a gain=1 buffer.. Is the EVM's output 5V only? [it should be..]

EVM is 5V only, if you want 10V you have to cut traces....

[opa627bm]

These eval pcbs had no effort put forward to optimise the precision and stability. They are literally for plug and play to see if the system they are attached to would even work.

If you read the wiki page carefully you find this comments about the power supplay options:

"POWER SUPPLY CONSIDERATION
Use a USB-C charger or other USB-C source to power the board. You should see a Green LED. Alternately, 5V can be applied between VUSB and DGND from a bench supply. This will power the isolating LMT8048 module, providing isolated power downstream. Alternately, the downstream regulators can be back driven at VPRE/AGND (Max 20V) or at V+/AGND (Max 16V). AGND is the Reference ground, so this approach is not isolated."

This means you could see the USB connector and the isolation as an optional bonus.
Besides that the reference itself is put on a milled out island to isolate it from mechanical stress.
With a little bit of grounding and shielding pretty much every level of noise performance should be achievable if an appropriate power source is used.

One last note: An EVAL board is meant to (more or less) quickly evaluate the functionality of a part which this one clearly does, if you ask me...
If a demo circuit is meant to deliver the full performance one would call it a reference design which would in case of such a precision reference more circuitry like EMI filters, output buffers or a specific ADC / DAC...

Cheers

Andreas

Hi, I have receive my 2nd EVM so I am going to by pass the USB supply and see if I can have a better result.

[opa627bm]

Anyone here modified the board to 10V output ? I finally picked up my 2nd board under a tree near B5 and cut the BUF_S to BUF_F and made the datasheet recommended adjustment. the output was 9.888XXXV which is far from the spec. I dont really want to switch out parts... so if anyone made the same mods. let me know.

[sahko123]

Looks like the output may be loaded possibly what exactly did you change?

[opa627bm]

Looks like the output may be loaded possibly what exactly did you change?

I cut the BUF_S that was connected to BUF_F, connect it to TP7 and connect TP6 to GND to form a 10V .
The output is not loaded , it is measured from a DMM7510 and I took the setup to ADI and verified the same result...

[iMo]

I would also disconnect the 7->5V divider (R1/R2), see below.

[sahko123]

You wont get 10V anymore this will result in 6.6V*2 because the op-amp divider is a divide by 2. The way to get 10v is to use the 6.6V to 5V divider and multiply it by 2

[iMo]

You wont get 10V anymore this will result in 6.6V*2 because the op-amp divider is a divide by 2. The way to get 10v is to use the 6.6V to 5V divider and multiply it by 2

Divide by 2? A high time to see the datasheet..
Thus 4 resistors involved in 7->10V output??

[branadic]

Thus 4 resistors involved in 7->10V output??

That is exactly what Eric Modica presented at MM2021:

You still have access to the 6.6 V raw zener output, which as we have verified has equivalent noise to the ADR1000. If you want to buffer that out to a 5 V converter compatible voltage you can huck up the ouput buffer to VDOUT and you have the worlds first absolut accurate ovenized voltage reference. If you would like to gain that up, if you would like 10 V for talking to a DAC or to your own home roled converter, you can use this trim divider here, R3 and R4, to put this amplifier in a gain of 2 to get 10 V out.

-branadic-

[sahko123]

This is as per the datasheet specifically the resistors are matched to 0.05% typical

[branadic]

Haven't seen an official datasheet yet, but LTspice already contains ADR1001 Spice model.

-branadic-

[iMo]

The ADR1001 chip has arrived.. And nope, I am not going to send it to Noopy, yet..

[Noopy]

So sad... 
 
Where/How did you get it?

[miro123]

Haven't seen an official datasheet yet, but LTspice already contains ADR1001 Spice model.

-branadic-

Really strange marketing and communication. Something similar happened recent wit ADR1399
First EVM, then leaked info than samles and last but not at least the datasheet.
The same think happened with ADR1001 - I assume that analog development  are switched to agile.  Documentation and final parameter will be published later on.

[iMo]

There is none model in latest LTSpice (for Win64). You may find the model in the "beta version" for win64.
PS: (the ADR_OUT oscillates without the C3=1uF, 10nF or 100nF between BUF_F and BUF_S does not help either)..