Other Parts Discussed in Thread: LAUNCHXL-CC2650
Hi forum
I have designed a system based on the CC2650EM-7ID-RD comprising of 2 layers,i have copied the reference design as it is having same trace width,distance from surrounding group plane and balun values.
I just want to switch to a 4 layer board.I would like to keep make the 2nd layer my first ground plane with similar stacking height as the original design I-e 0.73mm of FR4 dielectric between 1st signal layer and ground plane.
Proposed Stack-Up:
1st layer:Signal layer of 35um copper thickness with ground plane on the remaining area around the signal tracks and RF traces,balun
0.73mm of FR dielectric pre-preg
2nd layer(1st ground plane) of 17.5um copper thickness with some signals but mostly a continuous ground plane
400um of FR4 dielectric pre-preg
3rd layer: VCC or 3.3V(Power plane) of 17.5um copper thickness
365um of FR4 dielectric pre-preg
4th layer:(2nd ground plane) of 35um copper thickness with some signals but mostly a continuous ground plane
Do I have to change my trace width and match my line impedance accordingly?
I have a confusion with my understanding if I keep the distance from the first ground plane the same as the original design,why would it matter if I keep adding layers below the top 02 layers?Actually my new design stackup is a superset of the original design.top 2 layers intact but just adding 2 layers below those 2 layers
My 2nd question is that what will be the change in decoupling capacitance if I switch to a 4 layer board with 1.62 mm total thickness?the AN-068 doesn't explain how to compensate for the stacking height alteration with addition or deletion of decoupling capacitance.
Looking forward for guidance,advice and help
best regards Ali
