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

5.1 System Needs More Power but PD Selects Lower Power PDOs

Assume there is a system that has the default settings discussed however the following are selected:

  • AUTO_NEGOTIATE_SINK.AutoNegMaxVoltage = 300d (15V)
  • AUTO_NEGOTIATE_SINK.AutoComputeSinkMaxVoltage = 0
  • AUTO_NEGOTIATE_SINK.ANSinkCapMismatchPower = 240d (60W)

When a USB-PD Source is connected that can meet the 60W requirement, the PD device always requests the 15V PDO contract and never goes higher. This is because at configuration (or set by the EC) the PD is being limited to 15V maximum. So regardless of the USB-PD Source offerings, the PD device never accepts more than 15V PDO.

15V PDO Requested and 20V PDO Ignored Figure 5-1 15V PDO Requested and 20V PDO Ignored