I can use the external Vref with my ADC now.
I noticed something that is confusing.
Vref+ is at 5 V & Vref- is GND, derived from a TL431 Regulator.
I am varying the ADC with a multiturn pot for experimenting, Pot uses Vdd..
I noticed that the ADC is jumping too much, just not a few digits. Even with the slow refresh I am using.
So I changed the Vref to internal VDD and it is stable. Stable enough for me although there may be a little changing but it is not noticeable due to slow refresh rate.
Is it because that the TL431 reference has noise?
The Vdd is a standard 7805. I believe it might have more noise.
And is the internal Vref is stable ( showing to be stable ) because the ADC noise and Vref+ noise is same coming from the 7805 and they cancel out each other ?
I noticed something that is confusing.
Vref+ is at 5 V & Vref- is GND, derived from a TL431 Regulator.
I am varying the ADC with a multiturn pot for experimenting, Pot uses Vdd..
I noticed that the ADC is jumping too much, just not a few digits. Even with the slow refresh I am using.
So I changed the Vref to internal VDD and it is stable. Stable enough for me although there may be a little changing but it is not noticeable due to slow refresh rate.
Is it because that the TL431 reference has noise?
The Vdd is a standard 7805. I believe it might have more noise.
And is the internal Vref is stable ( showing to be stable ) because the ADC noise and Vref+ noise is same coming from the 7805 and they cancel out each other ?