USB PD POWER Negotiations
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SLVA842–November 2016
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Copyright © 2016, Texas Instruments Incorporated
USB PD Power Negotiations
Application Report
SLVA842–November 2016
USB PD Power Negotiations
ABSTRACT
This document describes the Power Delivery (PD) contract negotiation in USB Type-C connections per the
USB-IF PD specification, and its implementation using Texas Instruments TPS65982 USB Type-C and
USB PD controller. USB PD is required in USB Type-C systems for power levels above 15 W (5 V at 3 A)
up to 100 W (20 V at 5 A) according to the specification. This application report describes the digital
communication between the transmitter and receiver ends of a connection support USB PD, the flow of
USB PD power negotiation, as well as the procedure for implementing and debugging USB PD
negotiations using the TPS65982 device and associated software tools.
The TPS65982 device is referred to throughout this application report, but the document also applies to
the TPS65981 and TPS65986 USB Type-C and USB PD controllers.
Contents
1 Introduction ................................................................................................................... 3
2 USB Power Delivery Specification for Sink and Source Capabilities ................................................. 3
2.1 USB PD Specification for Source Capabilities.................................................................. 4
2.2 USB PD Specification for Sink Capabilities (PDOs) ........................................................... 5
2.3 USB PD Specification for Sink RDO ............................................................................. 6
3 Tx Sink and Source Capabilities Mode Host-Interface Registers ..................................................... 6
3.1 Tx Source Capabilities Example Settings ....................................................................... 6
3.2 Tx Sink Capabilities Example Settings........................................................................... 8
4 Power Negotiation Flow..................................................................................................... 9
4.1 USB Power Delivery Specification for Power Negotiation Flow .............................................. 9
4.2 PD Trace Analysis of Power Negotiation Flow ................................................................ 11
5 Rx Sink and Source Capabilities and Active PDO/RDO Host Interface Registers ................................ 12
5.1 Modifying Tx Sink Capabilities to Negotiate Power Based on Actual System Needs.................... 15
5.2 Using Received Data and System Information to Renegotiate Power Contracts......................... 17
6 Debugging Common Power Negotiation Issues ....................................................................... 18
6.1 Failure Type 1—PDO1 Accepted With no Mismatch When High-Voltage PDO Available .............. 18
6.2 Failure Type 2—PDO3 Accepted With Capability Mismatch = 1 ........................................... 19
6.3 Failure Type 3—Rx Sink Capabilities Register (0x31) Reads all Zeros (0) ............................... 19
List of Figures
1 Tx Source Capabilities Register of TPS65982_HD3SS460_DRP_Source_Full_2_8.tpl........................... 7
2 PD Trace of Tx Source Capabilities....................................................................................... 7
3 Tx Sink Capabilities Register of TPS65982_HD3SS460_UFP_Full_2_8.tpl......................................... 8
4 PD Trace of Sink Capabilities after GSkC Command from Source................................................... 8
5 Successful Power Negotiation Flow from USB PD Specification .................................................... 10
6 PD Trace of Successful PD Power Negotiation........................................................................ 11
7 Status Register Read from TPS65982 Acting as Source............................................................. 12
8 PD Status Register Read from TPS65982 Acting as Sink............................................................ 13
9 Rx Source Capabilities Register Read from TPS65982 Acting as Sink ............................................ 13
10 Rx Sink Capabilities Register Read from TPS65982 Acting as Source ............................................ 14
11 Active PDO Register Read from TPS65982 Acting as Sink.......................................................... 14
12 Active RDO Register Read from TPS65982 Acting as Source ...................................................... 15
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