Electronics > Beginners
1V Reference @ 1ppm
<< < (4/13) > >>
beanflying:
The Maxim Ref I pointed to earlier in the thread https://datasheets.maximintegrated.com/en/ds/MAX6325-MAX6350.pdf is about 1ppm/mA typical (seems to be correct from my testing) so a 10k total divider would keep it fairly close to that or better and if you fit up the extra pot shown on the datasheet it can be tweaked up if needed without needing an op amp.
spec:

--- Quote from: beanflying on January 26, 2019, 10:53:33 pm ---The Maxim Ref I pointed to earlier in the thread https://datasheets.maximintegrated.com/en/ds/MAX6325-MAX6350.pdf is about 1ppm/mA typical (seems to be correct from my testing) so a 10k total divider would keep it fairly close to that or better and if you fit up the extra pot shown on the datasheet it can be tweaked up if needed without needing an op amp.

--- End quote ---
:) I was thinking on similar lines after you said that the loading would be very low. Will have a look at your suggestion.

If you had a 1V25 precision Vref (the lowest extreme precision voltage you can get), and connected a precision 250R and 1k resistor across it, as a potential divider, that would produce 1V with a source resistance of 200R (taking  the source resistance of the Vref as 0R), which would mean that a 200M load would only result in a delta V of 1uV or 1ppm, all other things being equal that is.
spec:

--- Quote from: beanflying on January 26, 2019, 10:53:33 pm ---The Maxim Ref I pointed to earlier in the thread https://datasheets.maximintegrated.com/en/ds/MAX6325-MAX6350.pdf is about 1ppm/mA typical (seems to be correct from my testing) so a 10k total divider would keep it fairly close to that or better and if you fit up the extra pot shown on the datasheet it can be tweaked up if needed without needing an op amp.

--- End quote ---
OK had a look at this. To have a 10K potential divider to produce 1V from a MAX6325 (2V5), would require 6k north  and 4K south. This would give a source resistance of 2k4, which would mean (ignoring the MAX6325 for the moment), that the minimum load for a 1ppm voltage delta would be 2G4.

I have also been thinking about the OP's requirement of 1ppm/deg C. But the specification we need is what voltage delta is acceptable over what temperature range and with what delta loading resistance, if there is a delta load- perhaps the load is fixed, which would simplify the design a bit.
tggzzz:

--- Quote from: Rafael on January 26, 2019, 12:50:25 am ---
--- Quote from: Wimberleytech on January 26, 2019, 12:45:42 am ---
--- Quote from: Rafael on January 26, 2019, 12:22:53 am ---Hello,

Does anyone have any suggestions on how to find / build a 1v @ 1ppm reference?

Thanks a lot!

--- End quote ---

I assume you mean: 1ppm/°C.  Over what temperature range???


--- End quote ---

You're right, sorry to forget this detail.

Range, around 23°C... I can imagine a hard task!

--- End quote ---

Are you concerned about drift over time? If so, you may need lengthy burn-in times.
beanflying:
Without wanting to go way down the rabbit hole of voltnuttery a full and complete spec of the OP's requirements would be needed or we are just speculating on the requirements outside the 1V @ 1ppm of ? (voltage, temperature, drift over time etc) and what is the references intended use? So some more info is really needed.

Just run over the rough numbers based on the 10K guess I used this morning. -

To get the divider of 6 and 4k (assumed dead accurate) you would actually get 0.9996 volts read assuming the nominal 2.5V 10Meg meter so it would need the compensation pot fitting to the circuit to tweak it accordingly if it's purpose is for calibration and if not the input impedance of the driven circuit needs to be taken into account regardless.

My couple of tweaked MAX 6350's I built have remained within spec and have been powered on now for over a year so they seem to hold up well after the first week or so of settling. There was some questions raised about the epoxy version available (ceramic is off the market) could be susceptible to moisture over tim but that is well into VoltNuttery @ Andreas level territory (nothing wrong with that at all btw)  ;)

Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod