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How to connect ADC pins to the ground plane?

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seyyah

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It's advised to connect an ADC's both AGnd and Dgnd pins to analog ground plane. What i wonder is is this also apply to reference inputs?

I have system that has a single 24V input and several outputs as shown in figure.
But I'm confused how to connect the grounds. I decoupled all outputs, they are connected at a point and as shown in figure. 5V analog, supplies analog circuits. 5V digital, supplies the digital circuits. 2.5V reference is the reference voltage input of the ADC (It's differential input). 10V reference supplies another circuit and that circuit's output is the input to the ADC. 12V also supplies other analog circuits.

I tried to separate the voltages to prevent sensitive circuits from being noise injected but ADC is a confusing part. What do you offer me?
 

Re: ADC grounding

Also without knowing your circuit deails, I expect that at least the analog voltages have a common ground at the ADC. Thus the schematic doesn't probably apply to your circuit. Furthermore, analog and digital ground have often separate pins at an ADC, but aren't allowed to have large voltage differences (e. g. above 100 mV).

Manufacturer reference designs, if using separate power planes respectively split planes at all, are ususally connecting them near the ADC. Cause the supply voltages usually have a common ground at the power supply too, separate supply grounds allover the board don't make much sense then.
 

Re: ADC grounding

I planned the power section as in the figure. So there's 24Vground, 12V ground, 5V analog ground, 5v digitial ground and reference's (10V and 2.5V) ground all decoupled. But i couldn't decide whether this scheme is good or how to proceed.

I plan to supply ADC all from the analog section because any difference at the grounds of avdd and dvdd causes to coupling of noise from the digital section of the adc to the analog section. but other digital circuits will be supplied from the digital 5v section. Digital and analog sections will be connected at a point far from the adc which will be probably at the main supply. But i could not decide about the VRef input of the ADC? Does the rule for Agnd and Dgnd als oapplies to it? Must i connect its ground to the agnd as well and with the shortest possible track? How is the inside situation of the reference voltage in the ADC?
 

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