Lesson 8: Sch & Layout Course.

[walid]

Hello Robert,

Do you pour GND on all layers after you finish routing and when it is not recommended to to pour GND?

Could you please let me know your opinion about my answer regarding seperating or not DGND and AGND?

Does Altium do the impedance matching automatically? If yes, any reference? How do you set the signle-ended impedance in Altium and use it across the whole design?

In the impedance calculator the track length is not taken in the calculation, which is not true! Isn't suppose that the length of track is considered?

Thanks in advance

[robertferanec]

1) No, I do not pour GND on all layers. I read some articles, that if you pour GND between tracks it may sometimes make the results worse (especially EMC). So, I use only full GND planes inside PCB and I have never had problems with it, so I keep using it that way.

2) "let me know your opinion about my answer regarding seperating or not DGND and AGND" - I went through our emails and could not find it. Please, could you point me to the email?

3) I do not use Altium impedance calculator. You need to ask your PCB manufacturer to give you the correct track geometry (width, gap) for specific stackup and then just use this geometry during layout to achieve required impedance. This is the way how then PCB manufacture can guarantee, that your PCB will meet the impedance requirements.

4) Track impedance is length independent (the other words, impedance doesn't depend on the length).

[hajri_abderaouf]

Hello,
i usually use ferrite Beads to separate different GND,always it had been a good solution,but for the last board i designed i had got noise on audio module,this problem was solved by replacing the ferrite bead with a resistance of 0 Ohm.
for Gnd plane,i always create gnd plane on all layer,i'm not sure that this is the better way to get best result,so next time i'm going to follow robert.
Kind regards.
Raouf