I'm designing a PCB that will utilize USB-C to supply power (5V/3A) to my board and have a few questions:

  1. What are the requirements to ensure a 5V/3A (15 W) supply to my device if I know nothing about the supply (i.e which default current supply case will occur if I'm charging from a laptop or other supply in which Rp is not known)?

  2. Is it possible to ensure a 5V/3A delivery of power without a USB-C Configuration Channel Controller or USB Power Delivery IC? Ideally I'd like to implement the basic layout seen below and tap from VBUS.

Standard Supply to Sink Connection


in which Rp is not known

This is the entire idea of Type-C basic connectivity. Your device must use some voltage comparator to determine the voltage level of Rp:Rd divider. That's how you "know" what the Rp is. Your device can take 3A only if you sense about 1.6V at one of CC pin, which corresponds to 10k - 5.1k voltage divider. To sense this condition, you can either use TWO analog comparators (maybe one comparator will suffice if charging-only function, not sure), or use a single CC-controller IC that does this job.


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