General > General Technical Chat
LM431 (TL431) 0.1-10 Hz Vp-p noise.
MasterT:
--- Quote from: iMo on June 13, 2023, 03:32:07 pm ---A "reference for 24bit ADC" means the Vref fluctuation (thermal, 1/f, other noise, long term stability, hysteresis, etc) is (well) below 1 LSB (0.15uV in your case, imho).
--- End quote ---
Not quite, noise 0.15uVp-p in sub 10 Hz range, this is why I'm saying "NO single Voltage Reference on a market for 24-bits ADC".
I'm considering one parameter only, it's written in the topic's name, so /aging /temp. stability /long-term / humidity - not to discuss, please.
I start this research during evaluation SD ADC from AD, and explain in another thread that there is No solution to get noise below 0.15 nVp-p
except using simple RC network filtering . You may continue to critisize this , but w/o offering alternative to RC filter, words would not have any sense to me.
TL431B is evaluated for one parameter only, and it's works exceptionally/ perfectly well - my SD ADC running almost for a week now
Comments to image: 3 TL431B in the test, one is connected to adc V.Ref input, two others - to two diff adc inputs.
Filtering is swithed off for all 3 at the moment of capture image, but I also tested with 3 identical (1500 uF + 10k) filters .
Wiggle lines (about 4 uV) similarity on both channels proves that I have a problem not with the filters but with variation on the input current at Ref. Input of the ADC. Strange things, DS says +-100 nA but measurements imply +- 3-5 nA absolute values, with 4 uV / 10k = 0.4 nA bumps
iMo:
With such a cheapo reference like the 431 you may put, say, 100 of them in parallel and the noise drops 10x, afaik.. :D
MasterT:
--- Quote from: iMo on June 13, 2023, 05:00:01 pm ---With such a cheapo reference like the 431 you may put, say, 100 of them in parallel and the noise drops 10x, afaik.. :D
--- End quote ---
You mean to build a "Godzilla" reference with 1 A current? ::)
I'm weighting costs of small auxiliary SD ADC to monitor those current bumps on reference inputs lines. To create "dual core" ADC, where main unit is sampling 2 channels w/o been disturbed by switching MUX to those lines, as I thought earlier. Same concept as ads1263 - can't get one for a year, out of stock.
dobsonr741:
I had good experience with the Zonri ADS1263 modules of CN origin. After replacing the sw reg on them.
iMo:
--- Quote from: MasterT on June 13, 2023, 08:46:02 pm ---
--- Quote from: iMo on June 13, 2023, 05:00:01 pm ---With such a cheapo reference like the 431 you may put, say, 100 of them in parallel and the noise drops 10x, afaik.. :D
--- End quote ---
You mean to build a "Godzilla" reference with 1 A current? ::)
--- End quote ---
There are the LM385-2.5 references, running well from 20uA current. That would be 2mA with 100pieces.. :)
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