I was looking at the Gerber Files for the Beagle Bone PCB rev C2, and found the Layer Stack-up table on the Fabrication Drawing layer (beaglebone_revC2_FAB.pdf), including some impedance control information. I know how to interpret the stack-up, but the impedance control part is new to me.
Can someone explain it to all of us?
Is this something I should be aware of when designing a custom board? If this is true, how do I know which traces should have controlled impedance?
I suggest you do a search on this information. There is a lot of information out there on PCB technology. This issomethign you need to be aware of when designing a board. It is particular important around DDR and USB type signals.
I did search, but I wasn’t able to understand the meaning of the numbers in the table.
Are those widths to be used on the test coupons of the PCB manufacturer?
In other words, should he make traces following that table’s widths and layers on each panel and measure 50, 90 or 100 ohms to guarantee process stability?
Impedance is controlled by the amount and characteristics of the dielectric material between the layers of the PCB and also based on the trace widths and where they are placed and where the ground under them is placed. preferably under the signals.Just look at the PCB information supplied with our boards. If nothing else, just copy it…