SLVSF62B November 2020 – September 2021 TPS25858-Q1 , TPS25859-Q1
PRODUCTION DATA
DFPs and DRPs fulfill the role of detecting a valid connection over USB Type-C. Figure 10-14 shows a DFP-to-UFP connection made with a Type-C cable. As shown in Figure 10-14, the detection concept is based on being able to detect terminations in the product that have been attached. A pull-up and pull-down termination model is used. A pull-up termination can be replaced by a current source.
For USB Type-C solutions, two pins (CC1, CC2) on the connector are used to establish and manage the source-to-sink connection. The general concept for setting up a valid connection between a source and a sink is based on being able to detect terminations residing in the product being attached. To aid in defining the functional behavior of CC, a pull-up (Rp) and pull-down (Rd 5.1 kΩ) termination model is used based on a pull-up resistor and pull-down resistor.
Initially, a source exposes independent Rp terminations on its CC1 and CC2 pins, and a sink exposes independent Rd terminations on its CC1 and CC2 pins. The source-to-sink combination of this circuit configuration represents a valid connection. To detect this, the source monitors CC1 and CC2 for a voltage lower than its unterminated voltage. The choice of Rp is a function of the pull-up termination voltage and the detection circuit of the source. This indicates that either a sink, a powered cable, or a sink connected by a powered cable has been attached. Prior to the application of VCONN, a powered cable exposes Ra (typically 1 kΩ) on its VCONN pin. Ra represents the load on VCONN plus any resistive elements to ground. In some cable plugs, this can be a pure resistance, and in others, it can simply be the load.
The source must be able to differentiate between the presence of Rd and Ra to know whether there is a sink attached and where to apply VCONN. The source is not required to source VCONN unless Ra is detected. Two special termination combinations on the CC pins as seen by a source are defined for directly attached accessory modes: Ra/Ra for audio adapter accessory mode and Rd/Rd for debug accessory mode.