Regarding the Ground loop for a mixed signal PCB

[subramanya.ap]

ground loop pcb

hi,

I wanted to know, whether a ground loop in a PCB will help for EMI/EMC. analog and digital grounds are seperated and an extra ground loop is running throughout. so will it help?

 

[Kral]

mix signal pcb

subramanya.ap,
I believe you mean ground plane, which consists of grounded copper either between traces or a solid plane of copper between layers of a printed wiring board. The answer is yes, it will help. The ground plane provides a termination point for electric fields. The ground plane will help reduce both susceptibility to EMI and emissions from your circuit. The ground plane will not, however reduce EMI caused by currents that result in magnetic fields.
Regards,
Kral

 

[subramanya.ap]

pcb ground loop

Thanks for your reply... I Have ground plane running throughout the PCB. But the gtround loop is only running at the edge of the PCB. it is connected to chasis. Analog and digital grounds are seperated, and they are shorted at a point. So i wanted to know the difference between having a single plane which covers all the grounds and having seperate signal and chasis. Because ground loop may create some EMI issues.

 

[cesare]

ground plane pcb loop

As I know it is better to have only one solid ground plane.

Usually mixed signal chip manufacturer reccommend to use distint analog and digital ground plane. This is to avoid that digital return currents corruts mv level analog signal.

However this plane splitting is not so easy to do if you have more than one mixed signal device.

The best solution is to have only one solid ground plane and define return current paths by accurate component placement.

See http://www.hottconsultants.com/

 

[kevpat]

ground loops pcb

Hi you should use chassis ground to reduce EMI emissions to the outside world through cables etc. You should have a seperate I/O and Signal ground. All your I/O connectors should be grounded to the Chassis ground through a low impedance path like a EMI gasket or grounded screw. Ground loops will not be a problem as you should not have the signal and I/O ground connected at any point and all I/O signals should pass through a Common mode choke before ebtering the I/O zone.