I/O Interfaces & Buses

Which describes USB Power Delivery (USB PD)?

  1. AThe source and sink negotiate voltage and current so that higher voltages than 5 V can deliver more power
  2. BIt carries USB data over power lines
  3. CIt always applies 20 V to every device to charge faster
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Answer: A. The source and sink negotiate voltage and current so that higher voltages than 5 V can deliver more power

Basic USB power is 5 V with limited power. With USB PD, after connection the two sides communicate over the CC wire and agree on a voltage and current the sink can accept before the voltage is raised. It is used to charge laptops and similar, and extended versions can deliver up to 48 V at 5 A (240 W). Until the agreement is made, the supply stays at a safe 5 V.

  • A. Correct. The latest version handles up to 48 V and 240 W.
  • B. It is not a power-line communication standard.
  • C. Applying a high voltage without negotiation would damage devices.
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