Hi,
in STUSB4500 if we are planning to use the chip for Power delivery and communication enabling circuit, then will it be necessary to do adjustments in the Vbus when and external 3v3 is applied to the Vsys pin.
In case of a Power delivery available port, then the Vbus will be able to power up the Vdd.
But in case of a non PD cable comes in contact for communication, for the ATTACH and AB_side detection, wont we require an external power on the Vsys pin…?
whether the ATTACH and AB_ Side pin wont be sufficient for communication circuit triggering.?
Have anyone tried this usecase for the STUSB4500.?
DO you have any suggestions on the same…?
Please share your views on this…
Best regards,
Akshay Vavukkal
I am learning in a new (interesting) world of PD and have ordered the different materials to study this in detail.
Related to your question the specification is making clear what happens in that case. It spends considerable content on TYpe-A, Type B and Type-C cables and how to react. The “Sources Shall run the cable detection process prior to the Source sending Source_Capabilities Messages”.
The cable detection (after insert) will trigger to set vSafe5V (Safe operating voltage at 5V) on VBUS. The current level is depending on the type of cable detected. The STUSB4500 is not involved in that detection (actually it should ignore any messages if it gets one). That way you always get 5V (backward compatibility) and thus VDD for STUSB4500.
VSYS seems to be only needed if you want to program the STUSB4500, without being connected to a USB-power source at all.
If you want USB-PD to work over Type-A, you’re short of luck. There is a standard for that, but it’s substantially different electrically to how USB-PD over Type-C works. My understanding is also that it’s very uncommon.