STUSB4761 rejects PDO with 5A

[mrs]

We try to use STUSB4761 for a 100W USB-PD Source.

Test setup includes our PCB with STUSB4761 as power source, an e-marked 5A rated cable and Acroname "USBHub3c Pro Edition" as power sink.

According to the log (see Attachement) of the USB PD communication, STUSB4761 advertises in the 5th PDO 20V/5A but if I try to select this PDO the request is rejected.

Is there anything wrong with this configuration?

    

[MiBA]

Hi 

A power source can only propose the 5A if the cable is detected other way the source PD0 is 3A max 

so on source side 

on one CC pin you must see provided typeC current RP STD,1.5 or 3A , and on the other you must see pull down Ra from the cable 

from messaging POV you will see cable ID identification messages 

BR

[mrs]

Hi

We chose STUSB4761 because of its capability to check the cable. But it is exactly this case which does not work:

• If we use a cheap cable without e-marker, STUSB4761 correctly advertises 20V/3A only, and if I select this PDO it switches to 20V (and switches off when increasing the output current above 3A, also correct).
• But If  we use a 5A rated cable with e-marker, STUSB4761 correctly advertises 20V/5A, but if I select this PDO it rejects the PDO and refuses to switch to 20V.
• After sending a soft reset, STUSB4761 somehow “forgets” to check the cable, advertises 20/3A only and switches to 20V.

Why this behavior?

And what does "POV" mean (could not find it in the USB PD standard)?

Best regards

[NBALL]

Hello

There are multiple things that I don't understand.
Snapshot shows 'powered' for VCONN, which means that stusb4761 will supply vconn and check for the cable (i.e cable is not captive). If cable is 5A, capabilities will be 5A max, otherwise, they will be clamped to 3A.
In trace you share, source-cap @20V is 5A but there is no cable messages (SOP').
To reproduce such trace I need to turn Vconn to 'grounded', which is supposed to be used when cable is captive.

Then, when sink request 5A, it is accepted, I do not observe reject message.
1/ can you please confirm that after flashing the device, DUT is powered cycled ?
2/ Can you please shared NVM content using 'export NVM file' button ?

3/ may I know which sink is used ?

Best regards

Nathalie

[mrs]

Hello Nathalie

Thank you for your reply.

Our PD source will have a standard USB-C receptacle and is to be used with a standard, 5A rated and e-marked USB-C to USB-C cable, no captive cable will be involved.

To your questions:

1) Yes, I can confirm the power cycle

2) see the  attachments (read out this morning) 

3) We use Acroname "USBHub3c Pro" as sink for our tests. I'm already in contact with them because of the missing cable messages (SOP') in the trace.

Additionally, I'm going to do the tests with other sinks, for example the STUSB4500 evalboard.
Do you know other suitable equipment to test USB PD sources?

Best regards, Michael

[NBALL]

Hello

I don't have this acroname tool on my side.
If you have stusb4500 evalboard, it can be used for checking the behavior with 5A/3A cable.

STUSB4500 can be configured with 3 PDOs: 5V-3A/15V-3A/20V-5A
If 5A cable is used, 20V will be negotiated, otherwise 15V will be selected.

Using NVM you shared, I do observe properly this behavior.

Best rgeards

Nathalie

[NBALL]

Please also note, vs one of your first post, that there is never a cable check after a softreset.

Cable check occurs after attach of HardReset (i. e after vbus raises)

Best regards

[mrs]

Thank you.

But why does STUSB4761 not keep the obtained cable information until detach?

Best regards

[NBALL]

STUSB4761 keeps cable info till VBUS power cycling occurs, as per USB-PD spec requirement

Best regards

[mrs]

Thank you.

Which testing equipment do you use?

Best regards