ADR1399 reference

[branadic]

Attached are multiple noise measurement of my ADR1399-PWM-DAC. Please replace µV by nV and you end up with about 2 µVpp.

-branadic-

[Kleinstein]

The noise looks good, with quite some of the peaks that are realatively short, possibly on a time scale where a little more filtering can help.
The real question is how good the long term drift will be for the TO46 version.
Let's hope it is driften less than the expected date for availabilty.

[deepfryed]

I have one ADR1399H-EBZ on order from Mouser, they say ETA end of September. Let's see.

[maxwell3e10]

It is in stock on Digikey in TO46 can right now

https://www.digikey.com/en/products/detail/analog-devices-inc/ADR1399KHZ/15848880

[gamalot]

Four ADR1399KHZ from Digi-Key have just been delivered. My money is running out and I can't afford more. 

I don't know what printing technology in 2023 can make the silk screen on top look so blurry and dirty!

[iMo]

Does not look like ADI's quality.. A fake?

[gamalot]

Does not look like ADI's quality.. A fake?

No, that just proves that they must be genuine, perhaps using eco-friendly printing techniques. 

[branadic]

Looks really weird, as it is ADR1399 with LT logo instead of ADI logo, beside the poor printing quality.

-branadic-

[gamalot]

Even the thermal shield itself is not the same as before, what happened? 

[iMo]

..ask your supplier..

[NNNI]

@branadic
Have you already posted about the ADR1399 PWM DAC somewhere? I would love to learn more about it. I've recently been playing around simulating something similar using a passive 3 pole RC filter (3 stages of 10K/100nF C0G) which does indeed reduce ripple, but assuming I want 1uV settability, I would need a 23-bit resolution PWM signal. While that is possible, it pushes the PWM frequency very low, and I'm not sure how to make a practical implementation. Perhaps reduce settable resolution to 10uV?
@gamalot: Someone I know also just got an ADR1399, the printing was similarly crusty but the package looked to be in better shape.

[Kleinstein]

From the picture the "printing" look like laser writen, with small dot matirx depressions.  Getting the LT logo is indeed odd.

[Andreas]

While that is possible, it pushes the PWM frequency very low, and I'm not sure how to make a practical implementation. Perhaps reduce settable resolution to 10uV?

Hello,

it is all in the LM399 thread.
We are using Sigma Delta modulation for the PWM.
So it is possible to do several kHz @8 Bit PWM with 24 bit resolution.

https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg2189460/#msg2189460
https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg1955149/#msg1955149
https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg2200098/#msg2200098
https://www.eevblog.com/forum/metrology/lm399-based-10-v-reference/msg2082544/#msg2082544

with best regards

Andreas

[iMo]

@Andreas - perhaps you may open a new thread, like "x399 based PWM voltage standard" or something like that, and start with an update on the effort you, branadic and others did (like the latest schematics, firmware, etc). Otherwise it remains hidden in the rather long 399 thread..

[Kleinstein]

The PWM DAC part is not directly related to the reference, only indirectly through the voltage and noise level / stability expected.
AFAIR the LM399 10 V ref. part is not a classic PWM DAC, but in the 7 to 10 V amplfier feedback. This adds some limitations but also gets up from 7 V to 10 V without critical resistors setting the gain.
A more universal voltage source would more use 2x7 V to start with 14 V and than use a more conventional PWM DAC to get the 14 to 10 V (or another voltage) step.
Filtering would likely use film capacitors of some 1-10 µF, maybe even PP types to get fast settling / low DA.

[dietert1]

That's what i started building long time ago. There is an array of 10 LM399 to generate 14.1 V and to control the mains power supply that is built as a bootstrap amplifier to 19 V. There is an aluminum enclosure.
The 19 V will be used to implement the main PWM switch with a dual n-channel FET. I got the control board already with a 16 MHz MSP430 with isolated RS232, the PWM filter and the ripple compensation switch. So little missing. Just need to finish the main PWM switch and it will be a voltage calibrator.
The LM399 array has been powered for one or two years now and was already used for many different precision measurements.

Regards, Dieter

[gamalot]

From the picture the "printing" look like laser writen, with small dot matirx depressions.  Getting the LT logo is indeed odd.

Yes you can even feel the rough surface with your fingertip. At least on voltage reference components, I would prefer LT's logo to be there instead of ADI's.

[JodelJonny]

I just recieved my ADR1399 from DigiKey as well and it looks the same.
Unfortunately they were out of stock of the NOMC 8x10k Resistor arrays. If I can find one of those and a little bit of time I am going to build a second ADR1399 10V Ref.
Number 1 has been running for approx. 2800h.

I am very sorry that I havent uploaded any PCB/Gerber files yet. As this was my first real KiCAD project they are a mess and need signifacant work to be really usable.

[KT88]

There is a PCN related to the top marking:
https://www.analog.com/media/en/PCN/ADI_PCN_22_0025_Rev_-_Form.pdf

[Grandchuck]

How about counterfeiting?  Laser marking might discourage it.

[gamalot]

There is a PCN related to the top marking:
https://www.analog.com/media/en/PCN/ADI_PCN_22_0025_Rev_-_Form.pdf

It seems that there is no mention of the change of the logo.

[NNNI]

In case someone is interested, a slightly more high resolution picture of the laser marking. The carbonization, I assume, is because of the laser process itself, but is it a useful side effect or intentional? One can only guess.

[Echo88]

20€ on Mouser and the marking looks like piss in snow.

[iMo]

ADI hired a special tattoo saloon in Parañaque City..
PS: it could be it is a novel anti-counterfeiting technology..
Or, simply they reuse their existing laser engraver - all other epoxy and metal chip's markings are laser engraved.

[Kleinstein]

The relatively exotic plastics for the case could be tricky with conventional printing. With a relatively low volume product the laser labeling makes absolute sense, as there should be little fixed costs.