Electronics > Metrology

ADR1001 - Ovenized Voltage Reference System

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iMo:

--- Quote from: magic on March 29, 2023, 10:28:37 am ---I expected ADR1000 with resistors integrated on-die, some cheap R2R dual opamp from Analog and a bunch of wires jumping back and forth.
Maybe the package is too small for that. Such design would also need a few MLCCs.

--- End quote ---
That hybrid solution would be a pretty expensive device these days, I am afraid. They targeted (end 2022) $60, what is the price of an LTZ/ADR1000..

Kleinstein:
Not having large capacitors is a good point. The standard LTZ1000 circuit uses quite some capacitors, especially in the temperature regulation. Even when integrated on the chip the termal system is relatively slow and ideally would like rather long time constants in the regulation. Getting this with the limited on chip capacitors is tricky. One the other side the heater is using transistors instead of a resistor. This makes the heater much more linear and thus simplifies the regulation.  The LM399 also gets thermal regulation without large capacitors.

For the voltage loop not having a normal OP-amp can even simplify the compensation, as the LTZ1000 system has a gain of some 200 from the transistor that make the compensation with a normal OP-amp tricky. Here the ADC1001 could likely use a simple dominant pole compensation and no large capacitor needed.

For the extra output OP-amps the circuit looks large. In part this could be from splitting it between the temperature regulated part in between the heater to get low drift and the output stage that ideally has some distance to the reference and distribuited heat at the outside.  One should still avoid drawing much current from the OP-amp as the extra heat on the die could disturb the reference. So the position of the extra gain setting resistors at the op-amp is odd. I would really have preferred the resistors connected to the inverting input instead.

iMo:
An update..
Note:
34401A, 100NPLC, 10M input
7.1.23 powered off for 10minutes
24.1.23 powered off for 20minutes
18.2.23 powered off for 16 hours
5.3.23 powered off for 20minutes
17.3.23 - the first "metro-LAB_A measurement" Vref = 9.999.895 Volt, Fluke 8588A, powered off for 3 hours

Andreas:
Hmm,

-1.7 ppm in 2.5 kHrs looks better than my ADR1000 with -2ppm/srqrt(kHr)

with best regards

Andreas

iMo:

--- Quote from: Andreas on April 08, 2023, 06:40:05 am ---Hmm,

-1.7 ppm in 2.5 kHrs looks better than my ADR1000 with -2ppm/srqrt(kHr)

with best regards

Andreas

--- End quote ---

Sorry Andreas, that is what I see here.. Perhaps the ovenized on-chip resistors make the difference? Anybody else is measuring the ADR1001???

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