Beyond the supply and source requirements, there are additional mechanisms to meet safety standards when using >100W applications. Specifically, there is an additional requirement on the cable to support EPR. It is no longer optional to have the EPR-compatible cables visibly marked using the logos shown in Figure 42; instead, consumers can identify cable supports up to 240W safely through the logo on the cable itself. Typically, this means that the cable design may include higher-voltage-rated bypass capacitors and additional snubber circuits to reduce transients and ringing that may be more likely to occur at the higher voltages. It also means that 5A-rated cables will become obsolete; eventually, the USB-IF will no longer certify the original 20V/5A cables. This decision is will move the market to a state where all 5A cables are EPR-capable, and reduce consumer confusion around cabling issues. The cables are backward-compatible with older USB ecosystem devices, assuming the use of a USB-IF-certified USB PD controller.

With >100W applications, it’s important to highlight the restrictions for entering EPR mode before accepting the contract. The purpose of the new handshake guarantees that a single mistake in the handshake cannot lead to an EPR contract (in order to satisfy safety regulators). This new handshake ensures that legacy sinks cannot accidentally request an EPR contract.