Normally your UFP and DFP would have methods of sensing the CC ports voltage to adapt and act accordingly. The end device, or UFP has resistor values for Rd. Your power source, or DFP has resistor values for Rp. Image Sources provided by Microchip Application Note: AN1953 To illustrate this as an example Sparkfun has a USB-C breakout board that has the two resistors needed to pull up to 3A from the USB-C source power supply, here’s the part and the schematic: What I’m telling you is just slap two 5.1K 1% resistors on both the CC lines tied to ground on the connector of your end device and now you got 5V at up to 3 Amps and let 'er buck. This communication goes both ways, USB Type-C standards also has a specification standard for the power source, or Downward Facing Port (DFP) using two resistors to tell your end device what amount of current can be sourced, but we’re not really getting into that.Īlso USB Power Delivery(PD) has a standard digital handshake devices and their power sources can use to negotiate to raise the power above 5V for higher wattage and current, that’s separate from this and we’re not going to talk about that neither. What I’m writing about today is a simple way to get 5V at up to 3A, power supply permitting using the USB Type-C standards for current sinking end devices from just two resistors on the USB-C connector on your end device, otherwise known as Upward Facing Port (UFP)
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