STUSB4700 - Default 5V on VBUS not present if nothing connected to output connector

[calugarfinias]

Hello,

Ive designed a PCB with a STUSB4700QTR as a source following the datasheet ref design.

The scope was to use the board as a charger with PD.
When I plug a USB C phone on my source connector, the board deliver 2.2A at 9V on VBUS and the phone charge.
The issue is that when nothing is plugged to the source connector, the voltage on the VBUS is 0V. The default 5V on the output is not present.

I measured the voltage between the transistors T2 and T3 and it is around 5V, the T3 block the current (Is open)

I also checked other PD source devices and they deliver a default 5V on their ouput even if nothing is connected. 
Because logicaly if a device is completly depleted, it is not able to communicate via the CC lines until its internal PD IC is on. So for me the STUSB4700 should provide a default 5V.

So am I missunderstanding how the IC and the PD should work? Can someone help me please?

Thank you 🙂

[NBALL · Accepted solution]

Dear Calugarfinias

As per TypeC specification, sources are so called 'cold socket', which means that till a physical connection between source and sink is not valid, VBUS is not present. PD devices shall first comply with this TypeC requirement.

Source TypeC which has by default 5V is a corrupted source. When sink battery is fully depleted, it should be in 'dead battery mode' (please refer to TypeC specification), to get Vbus at 5V from source.

STUSB4700 complies with those requirements: that's normal that you do not get 5V when nothing is connected.

Best regards

Nathalie