SDAA265 April   2026 TPS26750A

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Applicability to other TI USB-PD Controllers
    1. 1.1 USB-PD Sink Introduction
    2. 1.2 Autonegotiate Sink Purpose
    3. 1.3 Definitions
  5. 2Fields Covered
  6. 3Autonegotiate Sink Basics with Examples
    1. 3.1 Auto Neg RDO Priority (ANRDOPriority)
    2. 3.2 Auto Compute Sink Min Power and Auto Neg Sink Min Required Power
    3. 3.3 No Capability Mismatch and Auto Disable Sink Upon Capability Mismatch
    4. 3.4 Auto Compute Sink Min Voltage and Auto Neg Min Voltage
    5. 3.5 Auto Compute Sink Max Voltage & Auto Neg Max Voltage
  7. 4Autonegotiate Sink Basics with EPR Examples
    1. 4.1 Systems Requiring ≥140W
    2. 4.2 Sink Path SPR to EPR Transitions
  8. 5Common Mistakes or Unique System Constraints
    1. 5.1 System Needs More Power but PD Selects Lower Power PDOs
    2. 5.2 System Supports EPR Power but PD Keeps Selecting 20V PDOs
    3. 5.3 Setting the Min Voltage and Max Voltage to the Same Values
  9. 6Advanced Autonegotiate Sink Examples
    1. 6.1 Downgrading to 5V Fixed PDO
    2. 6.2 Autonegotiate Sink With Interrupt Driven EC
    3. 6.3 ANeg: Auto Negotiate Sink Update
    4. 6.4 AUTO_NEGOTIATE_SINK Register
      1. 6.4.1 AUTO_NEGOTIATE_SINK Usage Example 1
      2. 6.4.2 AUTO_NEGOTIATE_SINK Usage Example 2
      3. 6.4.3 AUTO_NEGOTIATE_SINK Usage Example 3
      4. 6.4.4 AUTO_NEGOTIATE_SINK Usage Example 4
  10. 7References

1.1 USB-PD Sink Introduction

USB Power Delivery (USB-PD) is an open protocol that enables intelligent, high-power transmission over a USB Type-C connector. In every USB-PD connection, two primary roles are defined:

  • Source: The device that actively provides power. Examples include a wall charger, a laptop's Type-C port, or a power bank. The source broadcasts the available voltage and current combinations (example 5V at 3A, 20V at 3A) over the Configuration Channel (CC) pin. The source is also responsible for detecting the connection or disconnection of a sink device.
  • Sink: The device that consumes power. Examples include but are not limited to a smartphone, tablet, headset, or a cordless power tool. The sink reads the power capabilities of the source and selects the best option for operation.

Once a connection is established, the source first outputs vSafe5V (default 5V) over VBUS. Then both devices being USB-PD negotiation by sending messages over the CC pin. The source sends a Source_Capabilities message containing one or more Power Data Objects (PDOs). Each PDO describes a specific voltage-current pair. The first PDO is always a 5V PDO with varying current depending on the USB-PD source the other PDOs can be anything from 5V up to 48V with currents ranging from 0.1A to 5A.

The sink selects the best PDO from the Source_Capabilities list and sends a Request Data Object (RDO) back to the source. The source either accepts or rejects the request. If accepted, the source adjusts the VBUS output to the negotiated voltage and current, and then sends a PS Ready signal indicating that the sink can safely consume the agreed power. For system designers, the sink side relies on a dedicated PD port controller to perform this negotiation. The controller can be pre‑configured to request power autonomously, without involving a main processor. That is exactly where the Autonegotiate Sink Register becomes valuable – by allowing designers to pre‑set voltage limits, minimum power, and other parameters, the PD controller can safely and automatically secure a power contract, simplifying system design and improving reliability.