We are developing a product that needs to support (and be powered from) either a PD power supply or a non PD power supply - we do not know which the user will connect. Can someone please let me know what is the right architecture here? Thank you, Ni

[NDvas.2]

..

[NDvas.2]

Sorry I forgot to mention we wish to use the STUSB4500

[Winfred LU]

Please refer to STEVAL-ISC005V1

https://www.st.com/content/st_com/en/products/evaluation-tools/solution-evaluation-tools/psu-and-converter-solution-eval-boards/steval-isc005v1.html

STUSB4500 is a standalone USB PD controller. When connecting to a Type-C supply, it recognizes that the supply does not have PD capability, then automatically consume the power with Type-C only (5V 3A ex).

[NDvas.2]

Thank you @Winfred LU​ 

Two related questions for you, referring to the below paste from the STUSB4500 eval board schematics:

1. You are saying that even when a non PD power supply is connected, the 4500 will assert the VBUS_EN_SNK pin low and by that enable power to travel from the VBUS to the VSNK output?
2. Why are there two FETS (T1 + T4) here? Isn't one enough?

Thank you again,

Nir.

 

[Winfred LU]

1. Yes, with an exception that if POWER_ONLY_ABOVE_5V is set (to high), the VBUS_EN_SNK pin is only asserted when either PDO2 or PDO3 (both are PD only) contract is established.
2. T1 acts as an on/off switch ; T4 is to ensure Type-C receptacle is a cold socket - not turned on until something is plugged in

If removing T1, it will not compliant with the standard. Therefore, it is not recommended to remove T1.

If removing T4, there will be no negative voltage protection and no reverse battery protection. Thus, you may trade off keeping it against removing it based on your application needs.