50 ohms coplanar

[zolfaghari]

I am new to Nordic and want to design with the nRF52840. I have read this guide:

 General PCB design guidelines for nRF52 series 

used AppCAD to find the best width and clearance for the ground layer, but when I downloaded the default example:

https://nsscprodmedia.blob.core.windows.net/prod/software-and-other-downloads/reference-layouts/nrf52840/nrf52840-qfaa-reference-layout-1_0.zip






W = 0.8 and G = 0.125 in AppCAD 

The impedance is 45 ohms; is it OK, or did I make a mistake in calculating this?

[JONATHAN LL]

Test with Dielectric 4.8, you have it set to 4.6.

Regards,
Jonathan

[zolfaghari]

In the AppCAD calculator, I set the value to 4.6. In Altium, the value is 4.8 in the Stack Manager and verified the H and PCB material settings. Please confirm if 1.6 mm is correct for H and FR4 is correct for the dielectric. If these values are correct, the pad width and gap seem to be incorrect.

[JONATHAN LL]

Try changing the thickness T to 0.053.
 


Here is a calculation with Saturn


Regards,
Jonathan

[zolfaghari]

Thank you.
I set T to 0.053.

and the APPCAD error the T out of range but when use the online calculator or saturn  its work very well 

And APPCAD shows an error saying “T out of range”, but when I use the online calculator or Saturn, it works perfectly fine.

[JONATHAN LL]

Have not seen this issue, thanks for informing.

Regards,
Jonathan