Digital and analog ground

[doofus32]

https://obrazki.elektroda.pl/53_1163859803.JPG

I routing a PCB board that will look like the picture over. There are just one analog ground, the to analog ground, left and right, are to different setings.

The 8 pins IC over are DAC chip. The pins are as follow:

Pins 1-4: Digital input interface
Pin 5: ground
Pin 6: Vref
Pin 7: Vout
Pin 8: Vcc

The conection between the analog ground and digital ground must be where it is located. Also the IC sould not be moved.

The thing here is that and digital signal sould always have an return path (ground).

What is the right routing, the left one or the right one. I would preferd the left one.

I also have an situation were the IC is replaced with an NPN transistor for controling some analog signal on the board. The base to the NPN transistor is connected to a digital signal.

Also, is it okey to have closed loop in the ground plane. What I am thinking about is that around the analog ground, there will be an closed digital ground loop. I Think I have read some place, that that is not a good thing.

 

[rectifier]

For optimum performance, analog and digital ground must be connected to the single point.

Similarly, the closed loop must be as small as possible to reduce the induction of noise.

 

[Kryptonite]

what's the technical difference between ANALOG & DIGITAL ground????

 

[doofus32]

Yes optimal should the IC been placed where the connection between analog and digital ground is. But there can not be more like one connection like that, else the idea behind using different earth plane is gone. So what if you have more than one IC like the one over.