topic Re: KW24D512 USB Impedance in Kinetis Microcontrollers

KW24D512 USB Impedance

atillametetured — Fri, 21 Oct 2016 05:57:49 GMT

Greetings Kinetis experts,

I have a quick question. Is there a special reason why USB stick of KW24D512 has single ended impedance of 70 ohm and not 50 ohm for all lines?

Regards,

Mete

Re: KW24D512 USB Impedance

miduo — Thu, 27 Oct 2016 09:00:51 GMT

Hi,

Sorry I did not aware the USB impedance changed fr this part. From what I know what we always using is the 1:1 (50/50) which was found to provide the best performance for our FRDM, TWR and USB designs. Please let me know where indicate the impedance changed and I will help to confirm.

Re: KW24D512 USB Impedance

atillametetured — Thu, 27 Oct 2016 15:45:30 GMT

Hello Fang,

Thanks for your reply. When the below stack up is used for the board (from the open source .brd file)

Signle ended impedance of 8 mil lines become as follows (you need to zoom in sorry)

Am I missing anything? Different dielectric perhaps?

Regards,

Mete

Re: KW24D512 USB Impedance

jc_pacheco — Thu, 27 Oct 2016 22:01:03 GMT

It appears that this table is not accurate, please follow the specifications provided in the .brd file.

Re: KW24D512 USB Impedance

atillametetured — Thu, 27 Oct 2016 22:04:20 GMT

Hello Juan,

And which specifications are those please?

Regards

Re: KW24D512 USB Impedance

jc_pacheco — Thu, 27 Oct 2016 22:27:22 GMT

Hello Mete,

I mean the instructions provided in the .brd file (see NOTES section).

Where did you get the 8.000 of width?

You can also ask your manufacturer to get the 50 Ohm single ended requirement.

Re: KW24D512 USB Impedance

atillametetured — Mon, 31 Oct 2016 05:40:36 GMT

Greetings Juan,

Please find attached pictures, All are from LAY-28057;

Width = 8.000 tracks, combined with the stack-up supplied are 70 ohm single ended impedance for the board.

Regards,

Mete