Disabling all sink PDOs

[technoblogy]

I’m trying to design a very simple Power Delivery board based on an ATtiny processor that will display a list of the source power profiles, let you select one, and then deliver it to the output.

I have one question I'm stuck on. By default, when you connect the STUSB4500 to a USB PD source it selects the highest available voltage and enables the VBUS_EN_SNK line to deliver it to the output. In my application this isn’t ideal, because it could briefly deliver a higher voltage than wanted to an external circuit, before the I2C interface to the STUSB4500 has time to reset it.

I've tried setting DPM_PDO_NUMB to 0 and doing a soft reset, but this causes an error condition.

The only solutions I can think of are:

• Drive the gate of the output MOSFET from a microcontroller I/O line, rather than VBUS_EN_SNK, so I can control when the power is enabled. However, I would have to redesign the PCBs I’ve created.

• Reprogram the STUSB4500 NVM, but I’m reluctant to have to do this.

Is there a simpler solution I’m overlooking?