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PCB impendance

karimoviç , 12-06-2020, 10:02 AM
hello , what is the exact method to calculate or determine the impedance wof my board ??
Lakshmi , 12-06-2020, 10:28 AM
Ask PCB manufacturer or get the details of the materials and calculate yourself using some tool (Altium/Saturn PCB). Always prefer manufacturer data.

Dear Members!I would like to ask your opinion about impedance control on PCBs. I am hardware developer and I design high speed PCBs at a big company where we have more high speed interfaces on the boards, like oLDI, HDMI, FPD link, APIX, LPDDR4, MIPI CSI etc. Until now we did not use impedance control on our PCB-s. Our

Hello,I have few confusions I would like to be clear about. Thank you in advance for answering the questions. Why do we use Multiple Via on Ground plate and Power tracks? Is it just because of the increasing current flow? If so is there any rule for using the number of via's or position of via's on the tracks based on the

PS: most of these questions been already answered, so it's better if you could spend time and search here before posting which could save you time.
robertferanec , 12-08-2020, 02:35 AM
I would also add direct link to one of my videos, maybe it can help: https://youtu.be/O4T9y_aIItA
karimoviç , 12-08-2020, 03:03 PM
@robertferanec how i should chose the width / length of a tracks ?
robertferanec , 12-09-2020, 08:44 AM
Width: track width is often defined by required impedance and PCB stackup (usually you may want to use 50OHMs for digital signals - so based on stackup you will know what width you should use to route by 50OHMs). For powers you would like to use wide tracks. Also, often I route with a width (for example 0.1mm) and by the end of the design I make all the 50OHM tracks thinner to meet the required 50OHMS (e.g. I route all digital tracks by 0.1mm and when the layout is finished I change all 0.1mm tracks to a width which is required for my stackup to achieve 50OHM impedance, for example I change all 0.1mm tracks to 0.08mm).

If you are using only 2 layer PCB ... then you can for example use a little bit wider track than what is the minimum track for a cheap PCB. In this case your tracks will not follow required impedance - but it may be just fine for some simple PCBs.

Length: depends on what you are routing, but generally I use the length required to connect the pins. However, for some interfaces you may need to do length matching.

I would recommend to have a look at some design guides, for example you can start with something like this - google for "com express design guide":
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