PCB Design

[reza darabi]

Hi dear friends.

I have a few questions.

What is the concept of islanding on a PCB?

What places should POLYGON generally not be?

Why do you use PAD Grand in a row on PCB? Why not put PAD as a star?


I do not understand the concept of islanding BOARD.


Very very Thanks

[robertferanec]

Please, could you be more specific? What do you mean by "islanding" and "PAD Grand in a row". Maybe some screenshot could help.

[reza darabi]

Hi Robert.
I want to design the grand grid system?
Because it's said to be POLYGON in some hotspots. This POLYGON is the source of noise.
And these places that POLIGON should not miss is these places in the island.
thanks.

[robertferanec]

reza darabi, I am sorry, I do not understand what you mean. Maybe someone else can help?

[reza darabi]

Hi:
Where should POLYGON be? Where does POLYGON need?

[robertferanec]

Here are the cases where we use the polygons most:

- We use polygons mostly on power rails. This means, ideally you would like to have GND as one big polygon / plane under you whole PCB. Then, you may want to create local polygons for local powers under the components using that specific power.

- Also, you may want to use polygons on the tracks which are going to carry high currents.

- Other option is to use polygons to cool down some components (e.g exposed pad connected to a big polygon ... the heat from component can be transferred through the exposed pad to the polygon cooper and the big area of polygon copper helps cool down the component)

However, be careful with nets which are running high frequencies and are connected to polygons - wrongly used polygons can make your EMC/EMI worse.

[reza darabi]

Hello Robert
How exist STANDARDS (EX: ISO, MIL-STD, IPC, IEC) which determining "the maximum virtual CURRENT that can be obtained from a chip (output pin)" ?
maximum output current -> analog output.
maximum output current -> digital output.
maximum output current -> output pin of a sensor
Best Regards.

[robertferanec]

I usually check maximum current from/to pin in datasheet.