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?
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?