Debug missing USB power detection on custom board

RE: Debug missing USB power detection on custom board

Marjeris Romero — Tue, 04 May 2021 14:58:06 GMT

Hi Tobias,

I am sorry for the late reply. I took this case from Jonathan who is out of office right now.

Have you measured VDD with a multimeter? Could you send me a pdf file of your schematics? It looks like I am missing some kind of library in kiCAD because I am not able to see the connections to your external LDO right:

Best regards,

Marjeris

RE: Debug missing USB power detection on custom board

Tobias P — Sun, 18 Apr 2021 13:16:32 GMT

Polite ping. It'd be nice to have some information how to debug the USB power situation.

I'm leaning towards fixing the RF problem by simply using an off the shelf module, but that leaves the USB question - and I guess it might be useful to other reads of this forum, too.

RE: Debug missing USB power detection on custom board

Tobias P — Thu, 08 Apr 2021 16:16:28 GMT

Right, I'm aware that the RF design there needs improvement, thanks for the pointers!

I need the separate LDO as supply for the USB host IC on the same board (needs quite some current), so I thought it would make sense to use a common supply.

What do you mean by VDD conflicting? Are you saying the internal supply is trying to regulate VDD from VBUS (even though VDDH is tied to VDD)?

RE: Debug missing USB power detection on custom board

JONATHAN LL — Thu, 08 Apr 2021 15:12:55 GMT

Hi,

I don't see anything obvious in the schematic or the layout that could cause signal problems.
But I do advise you to check if the differential par impedance according to the USB standard.

The issue seems to be VDD conflicting from the USB and the nrf supply. I suspect that the ref design 1 is what you might want. Since there is an internal LDO on the nrf you shouldn't need a external one unless you need a different VDD supply for something?

However... your RF section needs some love. Ideally the antenna should not be placed so close to a large metal connector like the usb-c, but the layout of the first component of the RF section has a larger impact of how well the radio preforms. And since you have a 4 layer PCB we also recomend a cutout undeath the RF area on the two inner layers and use bottom as reference ground.

You see how the VSS_PA is connected to the C3 capacitor. This is a intentional design choice to improve filtering of the harmonics.
Ref PCB Guidelines:
"Pay attention to how the capacitor C3 is grounded. It is not directly connected to the ground plane, but grounded via VSS_PA pin F23. This is done to create additional filtering of harmonic components."

We do have a blog wit more info.

And do a ground pour on the top layer to increase the ground area. you can add vias to internal ground to reduce any possible ground loops. This can also be done on bottom layer if you want to use that at reference ground for the RF.

But if you just want to continue testing on the HW you have i would start by testing if VDD is conflicting.

Regards,
Jonathan

RE: Debug missing USB power detection on custom board

Tobias P — Wed, 31 Mar 2021 16:54:15 GMT

devzone.nordicsemi.com/.../co2.zip

RE: Debug missing USB power detection on custom board

Tobias P — Wed, 31 Mar 2021 11:42:28 GMT

Sure, thanks for looking at it!

devzone.nordicsemi.com/.../co2.sch

RE: Debug missing USB power detection on custom board

JONATHAN LL — Wed, 31 Mar 2021 11:38:00 GMT

Hi,

Can you share the schematics of your design ?

Regards,
Jonathan