USB-C Charging Device With Agnostic Power Supply
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 &quot;know&quot; 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.