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Precision voltage references...?
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Boscoe:
Hi all,

Money no object, what’s the best precision voltage reference you can buy easily (from DigiKey perhaps) and solder onto a PCB? This means modules are allowed but separate units are not. All I can find is the VRE range and the AD58x range from Analog. I know there’s the LTZ references how I’d like absolute accuracy as well as low drift. I imagine it’ll be a case of using the LTZ and getting it calibrated are a local lab?

Thanks
George
SiliconWizard:
If you were considering AD's offer with the AD58x, take a look at this: ADR4525
https://www.analog.com/en/products/adr4525.html
Not too bad.
tggzzz:
And getting all the other voltnut PCB and case issues sorted, and having it powered up for 6months before getting it calibrated, and... But why not have a look in the metrology sub forum, or search for ltz1000; there's a lot of information available.

Of course your first task is to define what specification you actually need, and not grossly over engineering a circuit.
Kleinstein:
The voltage needed can also make a difference - a stable 7 V from an LTZ1000 or LM399 are of limited use if stable 2.5 V are needed.
For the absolute accuracy a measurement (after soldering) with a good quality meter can be better than the usually specs.

Even for something simple as a voltage reference there are several parameters to look at: Voltage, TC, long term drift, hysteresis, noise and absolute accuracy. So it depends on the actual requirements.
David Hess:
The LTZ1000 wins hands down with the LM399 a distant second for temperature coefficient, drift, and noise, but not initial accuracy.

There are several Maxim parts with an initial accuracy of 0.02% or 1 part in 5000 and 1ppm/C which would be suitable for 4 digit applications without calibration and perhaps 5-1/2 digit applications with calibration.  Similar parts from Analog Devices are 0.04% but at less than half the cost and probably represent the sweep spot.

Watch out for low frequency noise.  Except in ratiometric applications, the only way practical way to remove it is to use multiple references in parallel.  This gives an edge to the LTZ1000 and LM399 even though they cost more and are more difficult to use.
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