STUSB4500 not triggering higher PD voltage – VBUS_READY remains false

[noor1]

Hello Team,

I am using the STUSB4500 USB Power Delivery controller in my design.

I have designed my board by strictly following the reference schematic provided in the STUSB4500 datasheet. However, the board is not working as expected.

I have already tried the following:

• Tested multiple firmware / configuration codes

• Verified all register values according to the datasheet

• Checked I²C communication and configuration writes

Despite this, the device does not negotiate higher PD voltages.

Issue Details:

• VBUS_READY always remains false

• Only default 5V is available on VBUS

• Higher voltages (9V / 12V / 15V, etc.) are not being triggered

I want to trigger a higher PD voltage, but the negotiation does not complete successfully.

Could you please help me understand:

• Possible reasons why VBUS_READY stays false

• Any common hardware/firmware or configuration mistakes to check

• Additional requirements for enabling higher PD voltage negotiation

Any guidance or suggestions would be highly appreciated.

Thank you for your support.

Best regards,

Noore Mujjasam

[Didier HERROUIN]

Dear noor1,

The  STUSB4500 is shipped with pre-programmed settings and if they fit to your requirements (especially the 3 default Power Profiles : 5V/1.5A - 15V/1.5A - 20V/1A), it can be used straight forwards.

So you are right, if you connect your board to standard chargers supporting 15V and 20V, the voltage should be negotiated to 15V or 20V.

Could you check the marking on the chipset ? It should be STUSB4500 (and not STUSB4500L which is USB-C only).

You can also probe :

- the activity on CC1 and CC2 lines to check it a negotiation between the Sink and the Source really takes place

- the voltage on VBUS to check if it is stuck to 5V or if some transient events occur

Finally, please send your schematics so that I can review them.

Best regards

[noor1]

Please review the schematic in attached pdf and let me know if you have any requirement from my side.

[Didier HERROUIN]

Dear noor1,

There must be no pull-down on CC1 and CC2 lines (you placed 5.1k resistors) : this is probably the root cause of your issue. Please confirm.

The rest of the schematics is perfect.

I assume that 3V3 comes from another part of your schematics (the pin VSYS could be also connected to GND). and that R147 and R148 are not mounted.

[noor1]

CC1 and CC1 are DNP and not mounted with STUSB4500. Yes 3v3 is coming from another circuit from controller, if we are not using controller board then vsys is connected to GND.

[Didier HERROUIN]

Please provide the marking code on the chipset (the whole reference which can be read on the top of the package).

You can also send the configuration file you are using, I could test it on my side.

When you mention  VBUS_READY stays false, do you refer to a pin or to the message PS_READY sent by the Source ?

Do you have a way to look at the communication messages between the Source and the Sink using a USB spy like STM32G071B-DISCO ?

For further investigation using a scope, please probe :

- the activity on CC1 and CC2 lines to check it a negotiation between the Sink and the Source really takes place

- the voltage on VBUS to check if it is stuck to 5V or if some transient events occur