separate 4 digital ground

[elec4]

hi buddies

i have 4 micro with 50 MHZ clock speed that control 4 brushless motor in one pcb...my question is that do i need separate each micro ground? my pcb dimension 100 mm * 100mm

 

[HTA]

Hi elec4,

this question is not possible to answer, because it depend what ground it is. Number 1 priority should be to separate analog and digital. Then to avoid that bigger switching current creates ground shifts for the micro(like from the motor commutation) or noise on the micro supply lines. In worst case an isolation between power switching and the micro is needed. If the GND and VCC lines having noise or spikes it will force the micro to be reset or even worst it changes RAM or register values. There a plenty of PCB design documentation of the web if you down have them already.

Enjoy your design work!

 

[andre_luis]

i have 4 micro with 50 MHZ clock speed that control 4 brushless motor in one pcb

Depending on which stuffs are you driving, you have to concern much more on splitting the power GND from the analog/digital grounds ( indeed, each one appart from another ) in distinct regions, but electrically connected. By the way, based on the picture above, are you placing 2 horizontal connectors for the external power devices in the middle of the board ?

 

[elec4]

Hi elec4,

this question is not possible to answer, because it depend what ground it is. Number 1 priority should be to separate analog and digital. Then to avoid that bigger switching current creates ground shifts for the micro(like from the motor commutation) or noise on the micro supply lines. In worst case an isolation between power switching and the micro is needed. If the GND and VCC lines having noise or spikes it will force the micro to be reset or even worst it changes RAM or register values. There a plenty of PCB design documentation of the web if you down have them already.

Enjoy your design work!

tnx for reply... i have 2 floor pcb ...first floor is power FET with ir2104 driver and second floor is micro and feedback zero crossing that connect with header pin in middle of pcb..i separate Power Fet Gnd from micro Gnd...My worries about if i not separate 4 micro gnd, May affect on other micro...sory for for bad language.tnx

 

[elec4]

Depending on which stuffs are you driving, you have to concern much more on splitting the power GND from the analog/digital grounds ( indeed, each one appart from another ) in distinct regions, but electrically connected. By the way, based on the picture above, are you placing 2 horizontal connectors for the external power devices in the middle of the board ?

i separate High power gnd (2kw..100 amp) from micro gnd...2 horizontal connectors for power supply of micro and connect pwm pin to ir2104 fet driver

 

[andre_luis]

It is necessary to have some level of imagination to understand the footprint of what exactly is being used in your project, but at first glance, the distance between the microcontroller ICs for the connectors, would be something to review, otherwise signals on these tracks will be prone to receive inducted interferences.

Another thing to consider is to use GND interleaved on the cable to shield the signals carried from one board to another, which is obviously not done in your case. Note that by adopting one side of the flat-cable connector GND, it accomplishes this task.