HELP!!! ANALOG GND Vs DIGITAL GND

[hemant2007]

analog ground vs digital ground

I want to know ans of following questions.

Difference between analog GND and digital GND ????

Why they should be isolated ??

Any other more information will make me more happy.

Thank you in advance.

 

[the_edge]

digital gnd

Did you check this:

 

[rogerynt]

gnd analog

For example in Dect digital cordless telephone both analog signal ( voice, speech ) and digital signal appears. However, without proper gnd separation, digital signal will leak to analog part of the circuit through gnd pins and hence degrade voice quality. Hum noice can be heard through the earpiece. Therefore, it's important to understand and carefully separate analog & digital gnd when doing pcb layout.

Roger

 

[Kral]

star point pcb

hemant2007,
Unless you're using optical or transformer isolatiom, the analog and digital ground s must usually be connected together at some point in the system. The secret to success is to route the ground traces so that current from the digital section does not flow throught the analog signal ground path. One way to ensure this is to keep the digital and analog paths isolated except for a single point connection at the power source.
Regards,
Kral

 

[hamdard]

analogue gnd

all the grounds must be isolated.

 

[moh_bim]

analog gnd

the difference is due to the frequency responce of ac over dc

it should be isolated so to prevent the circuit

 

[nwo4life]

привод analog gnd

hey,

You must separate your analog and digital GND's. If you can shield your analog circuits and GND from your digital circuits.

Why?
Well since your digital circuits are always switching, this creates noise and fluctuations in your power and ground rails. So there fore to reduce the switching noise you should protect you analog circuits by serparting GND's and other shielding methods.

 

[kevpat]

digitales gnd

As Kral has said earlier you MUST have at least one common point for your ground signals if not then you will have different references for analog and digital signals and there is a good chance your circuit won't work I used to use a star point system and tie my analog, digital and power grounds together at a star point at the power input point of the PCB. However in my last couple of designs I have used a single ground plane and been extra careful when routing signals in order to seperate digital signals from analog. What to remember is that the digital high frequency signals want to use the lowest inductance return path so if ther is no splits in your ground plane the return ground path for the digital signal will be directly under the signal trace, in order to maintain the lowest loop inductance. If you remember this simple rule then you can route digital signals well away from analog signals and as long as you have a solid ground plane the return signals will not interfere with the analog signals.