Question
1. For ADI's Reference chip, as below shown figure , Seems ADR423 and ADR440 is
our best part, whose TC is 1 ppm, noise is 1 uVpp. The initial Accuracy is only
0.05%, long-term stability is about 50 ppm.
2. In the PPT file, we use AD5791 to build a voltage source, Long-term
Stability is less than 1 ppm, TC is 0.05 ppm/degree. Is these parameter
AD5791's, or 1-ppm voltage source? If this parameter is for the 1-ppm voltage
source, I think this is unbelievable, because the selection of the voltage
reference(at AD8676's input) is hard. Whether we have test below circuit
figure2 and get the parameter as below red line shown?
Also I want to know what reference chip we used here.
Answer
1. In the voltage reference table, the TC figures are typical, the best max TC
reference is the ADR445 @ 3ppm/C max
2. The specifications underlined in red refer to the AD5791 only, they do not
include a voltage reference.
For my measurements I used a precision benchtop voltage source for the voltage
reference.