TPS25750: VBUS ripple when acting as source

Hi Blaž,

Could I please have a copy of your schematic? I will need to see how your system is setup in order to make any commentary on the ripple.

Regards,

Conner

Hi Connor,

Here is the schematics for the USB.

Thank you for providing this. I will review your schematic and provide feedback by the 16th, EOB.

Regards,

Conner

Hi Conor, 

Did you by any chance looked at the schematics?

Thanks,

Blaz

To clarify, you are sourcing 5V in the previous scope plot? If so, it is likely that the attached USB device likely momentarily drawing current past the current limit on PP5V, causing current clamping and the drooping of VBUS. If you take a current probe to VBUS, you can confirm this is what is occurring.

Regards,

Conner

Hi Conner,

I'm sorry for the delay. I finally managed to measure the current and it looks even weirder.

The current seems to drop when we have a voltage drop as if the device crashed. 

Two different spikes below (happens on almost all flash drives - 5 different tested):

Another interesting observation is that sometimes when we rotate the USB C flash drive it seems to work without those spikes.

Regards,

Blaz

What is providing the power for PP5V? I see a net labelled "5V" but do not see what is providing it?

And just to be sure, you are sourcing power in the above scenario?

Regards,

Conner

We have three different power sources here (AUX, PoE and USB). 

Since USB here is used for a flash drive (device acting as host so it's sourcing) we have to use either AUX or PoE. Both sources have a clean 5V output and it shouldn't affect the PP5V.

We also run our SOM from the 5V line so if the 5V rail would drop so low we would have other issues as well.

I'm attaching a schematic for the AUX power supply just in case. It's a 6A power supply but we are usually only sourcing around 10-15W (2-3A).

Thank you. Could you send me the configuration file you are using for your device (json format)?

I want to see if there could be a configuration setting causing this issue.

Regards,

Conner

Here is the JSON config file

{"questionnaire":{"version":"7.0.4.5","answers":[1,0,2,1,3,3,1,null,1,null,null,null,null,null,null],"options":{},"configID":"0000","vendorID":"0000"},"configuration":{"data":{"selected_ace":[{"register":6,"data":[0,0,0,0,0,0,0,0]},{"register":22,"data":[10,48,48,77,0,0,0,0,0,0,3]},{"register":50,"data":[1,168,42,44,145,1,38,44,209,2,0,44,177,4,0,244,65,6,0,0,0,0,0,0,0,0,0,0,0,0,0]},{"register":51,"data":[3,44,145,1,16,44,209,2,0,44,177,4,0,244,65,6,0,69,65,6,0,0,0,0,0,0,0,0,0]},{"register":92,"data":[0,12,0,0,0,0,0,0,0,16,0,0,0,4,0,0,0,4,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,0]},{"register":117,"data":[0,0,0,0]}]}}}

Are R202, R203, R204, and R205 all populated?

No, only the appropriate one are. Orientation detection and PD enumeration are working fine.