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ALM2403-Q1: How do I distinguish the digital and signal grounds on the ALM2403-Q1 development board?

Paul Chang
Prodigy 60 points
Part Number: ALM2403-Q1

Tool/software:

Dear expert,

I have a problem now
I see layout description in data sheet
The grounds for digital and analog signals need to be separated so that there will be better EMI effects.
But, how do I distinguish these grounds?

Because the same name is found on the square board.

  • 0
    TI__Guru 63331 points

    Hi Paul,

    Paul Chang said:
    But, how do I distinguish these grounds?

    ALM2403-Q1 resolver drivers are typically used in automotive application, e.g. traction inverter or similar. On the analog side, the GND may be tied to switching power supply, and therefore, it will be good ideas to separate the AGND and DGND. It is even better option to separate Power GND (switching power rails) from AGND and DGND. 

    Among all these different GNDs on PCB, they have to tie to vehicle's chassis at some point, which it should be a single GND point connections (single Ground pointing to avoid ground loop). The Power GND (PGND) from switching power supply typically used in heavy wire gauge. But your AGND or DGND will use lower gauge wire. For DGND node, you should use smaller wire gauge and run separate trace or plane on PCB (from AGND and PGND) - this is to create great impedance differences in the DGND connection.

    The high current is looking for low impedance path, similar to AGND as returned current path. DGND should be lower noises, high returned impedance path from AGNG and PGND. This is how you distinguish these GNDs - so the GND noises will not find its way in the PCB GND Plane. 

    You may use decoupling, filter, ferrite beads/choke, shielding, ground isolation, Ground Guard Traces, isolation amplifiers techniques etc. to separate DGND from AGND. Here are some video clips. 

    https://www.ti.com/isolation/isolated-amplifiers/products.html

    https://www.youtube.com/watch?v=3rxKZWQk_DY&t=258s

    https://www.youtube.com/watch?v=C51KoZhRaYA

    https://www.youtube.com/watch?v=cU115_OuZjY

    https://www.youtube.com/watch?v=652_8MsM0pI

    If you have additional questions, please let me know. 

    Best,

    Raymond