Hi,
I had exactly the same query as Ishida, before stumbling across this thread. However, it would appear that the impedance calculations shown in the excel spreadsheet attached in this thread gives different track/gap widths to that which are actually used in the layout.
For example, L1 USB traces are shown to be 5.3/9/5.3mils in the spreadsheet, but on the actual layout they're 5.3/3.7/5.3mils?
The same applies to the DDR3 routing, where 3.7/9/3.7mils is suggested in the spreadsheet for 100R diff traces on L1, but the actual layout uses 3.7/5.3/3.7mils.
Any reason for this? I'm guessing it will certainly make a difference to controlled impedances!
Regards,
Robin