I'm trying to implement a board that will use USB-C Power Delivery. We want to operate with 20V 5A input. If we know the source will always be at 20V, is it necessary to put a PD controller on the board? From what I've read, the PD controller is meant to protect the board from sourcing too much current when different sources are being used - since this is not the case for my application can I get away with not using a PD controller? Is there something that I would be sacrificing?
If VBUS is always >5V, this device cannot meet USB specifications. You are sacrificing USB compatibility and endanger users who might accidentally connect a standard USB compliant device (with PD or without) and fry it. If you want to implement "a board that will use USB Power Delivery", then implement the Power Delivery. In PD there is only one default and safe voltage, +5V. Anything else would be irresponsible hackery. If your source is permanent 20 V and up to 5 A, then it cannot be "power delivery", you should use a proprietary power jack for this.