Analog and digital ground connection with SMPS

[Murugesh_89]

Hi,
I would like to join the analog and digital grounds at only one place in the PCB using a 0E resistor in order to reduce the noise level in the design.

But i stuck up with the SMPS Negative connection with the circuit. I don't know whether i need to connect the SMPS(0V) with analog section or digital section.

I give the layout here..




Please clarify on above said points.

Please correct me if both the layout are poor and suggest me a best way to join grounds to have noise free system.

Thanks,
Murugesh

 

[KlausST]

Hi,

instead of using GND wires - like drawn - you should use a (split) GND plane.

A picture of the PCB should be more informative.

***
SMPS: an almost 360° cut around the SMPS circuit in the GND plane with then "entrance" near the power input and output lines helps to keep the noise away from other circuitry.

Voltage regulator for analog circuitry: keep it near the analog parts and set it to the same GND plane area as the analog parts.
At the regulator input there should be a relatively large ceramics capacitor to analog GND. Add a series L from SMPS power out to regulator voltage in to decouple from noise.

Klaus

 

[Murugesh_89]

Thank you.

Right now i am in the circuit design phase and will start the PCB design after the completion of schematic.

"Even though the we are having analog ground and digital ground, the will eventually be connected in the pcb but at single place to avoid some noises" - I think like this.

So my doubt is where the negative of the smps to be connected? Either at digital ground or analog ground? Which one is best?