USB Developer Days 2015
USB‐PD Practical Application:
Enabling Charge-Through Hubs
Terrance Shih
Product Manager
Taipei, Taiwan
November 17 – 18, 2015
November 17 – 18, 2015
USB Implementers Forum © 2015
1
USB Developer Days 2015
Session Agenda
• Introduction to Multi-Function Docking
• Traditional Docking Stations
• USB Type-C Advantages
• Charge-Through Docks
• Power Budgeting Basics
• Self-Powered vs Bus-Powered
• Legacy USB Port Considerations
• Power Policy
• Practical Charge-Through Hubs
• Design Considerations
• Protocol Walkthrough
• Exception Handling
November 17 – 18, 2015
USB Implementers Forum © 2015
2
USB Developer Days 2015
Multi-Function
Docking
• Traditional Docking Stations
• USB Type-C Advantages
• Charge-Through Scenario
November 17 – 18, 2015
USB Implementers Forum © 2015
3
USB Developer Days 2015
Traditional Docking Stations
• Separate Connections for
Data, Video, and Power
• Data and Video over USB
• Dedicated Power Supply
• Simplified Power Budgeting
• Fixed Power Supply for
either Self-Powered or BusPowered Configurations
• Fixed Power and Data Roles
• Used primarily with
Notebooks and Tablet PC’s
November 17 – 18, 2015
USB Implementers Forum © 2015
4
USB Developer Days 2015
Traditional Docking Scenario
Standard Display
USB
HDMI
Dock
USB
November 17 – 18, 2015
USB Implementers Forum © 2015
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USB Developer Days 2015
Traditional Docking Scenario
Standard Display
USB
HDMI
Dock
USB
November 17 – 18, 2015
USB Implementers Forum © 2015
6
USB Developer Days 2015
USB Type-C Advantages
• Data, Video, and Power over
a Single Connector
• Supports Thin & Light Platform
I/O Expansion Needs
• Enables Single-Connector,
Multi-Function Devices
• USB Type-C is Expandable
• USB-C is a connector spec and
by itself, you only get USB 2.0
and Legacy USB Power
• SuperSpeed USB is Optional
• USB Power Delivery is Optional
• Support for Alt Modes is
Optional
November 17 – 18, 2015
USB Implementers Forum © 2015
7
USB Developer Days 2015
Charge-Through Scenario
Standard Display
C
Mini
Dock
HDMI
C
C
USB
C
PD
C
PD
November 17 – 18, 2015
USB Implementers Forum © 2015
8
USB Developer Days 2015
Reminder: Be Mindful of User Expectations…
November 17 – 18, 2015
USB Implementers Forum © 2015
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USB Developer Days 2015
What Could Go Wrong?
November 17 – 18, 2015
USB Implementers Forum © 2015
10
USB Developer Days 2015
“Totally Useless”
November 17 – 18, 2015
USB Implementers Forum © 2015
11
USB Developer Days 2015
Power
Budgeting
Basics
• Self-Powered vs Bus-Powered
• Supporting Legacy USB Ports
• Power Policy
November 17 – 18, 2015
USB Implementers Forum © 2015
12
USB Developer Days 2015
Self-Powered vs Bus-Powered
• Self-Powered devices draw power from an independent, internal or
external power source separate from the USB Bus
• Power is limited by the internal or external power supply
• Bus-Powered devices draw power from the USB Bus
• Must meet appropriate USB Power Limits
• 500mA/900mA for Legacy USB
• 900mA/1.5A/3.0A for Type-C Power
• Other Voltage/Current Negotiable using USB Power Delivery
• Design Considerations
• Do I want to work exclusively in Self-Powered Mode?
• In Bus-Powered mode, does the USB bus provide adequate power for desired
operation?
November 17 – 18, 2015
USB Implementers Forum © 2015
13
USB Developer Days 2015
Bus-Powered Operation
• A Straight-Forward Scenario
Standard Display
• Power Source is Fixed
• Stay within the Source Limits
• PD Supersedes Power Limits
defined by USB 3.1 and USB
Type-C
Dongle
• Sources can Change Rp in operation
so you need to track it
HDMI
• If No PD, then Follow Source Rp
USB
C
• Pro Tip: Don’t Rely on 5V @ 3A
November 17 – 18, 2015
USB Implementers Forum © 2015
14
USB Developer Days 2015
Case Study #1
November 17 – 18, 2015
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15
USB Developer Days 2015
Self-Powered, Fixed Supply
• A Straight-Forward Scenario
• Budget for system power
consumption and charging
capabilities
• Source Capabilities are PreDetermined
Provides:
5V @ 3A
12V @ 3A
20V @ 3A
USB
• Considerations
• If the device uses a non-PD AC/DC
adapter instead of batteries or a
wall plug, consider that users may
try to use other adapters…
C
November 17 – 18, 2015
USB Implementers Forum © 2015
16
USB Developer Days 2015
Self-Powered, Variable Supply
• Source Capabilities? It Depends!
• Deduct System Power Consumption & Power
Losses
• Advertised Source Capabilities + System Power
Consumption cannot Exceed Source Capabilities
of the PD Adapter
• Available PD Tools
• Get_Source_Cap
• Supplied Voltages @ Currents (7 Combos Max)
• Externally Powered?
• Peak Current
• Get_Sink_Cap
• Externally Powered?
• Operational Current
Provides:
5V @ 3A
12V @ 3A
20V @ 3A
C
PD
Requires 6W
Advertises:
5V @ 1.8A
12V @ 2.6A
20V @ 2.7A
Mini
Dock
C
USB
C
• Capability Mismatch
November 17 – 18, 2015
USB Implementers Forum © 2015
17
USB Developer Days 2015
Case Study #2
Claim:
“The Dock has a cable with a male
USB-C plug extending from one end
that connects to the USB-C port on a
MacBook. The other end has a
female USB-C jack where the
MacBook's power adapter is
plugged — powering both the Dock
and the MacBook. Advanced USB 3.1
Power Delivery Specification circuitry
in the Dock manages the power in
and out of the dock, to each of the
ports, and to the MacBook.”
November 17 – 18, 2015
USB Implementers Forum © 2015
18
USB Developer Days 2015
Case Study #2
Facts:
1) Macbook USB Type-C Power
Adapter is rated at 29W
2) USB 3.0 Max Current is 900mA
@ 5V, or 4.5W per port
4x Ports = Up to 18W
3) The Hub, Card Reader, and
Ethernet controllers also need
power, and we still haven’t
accounted for the USB-C ports
or power losses…
November 17 – 18, 2015
USB Implementers Forum © 2015
19
USB Developer Days 2015
Supporting Legacy USB Ports
• Standard A USB ports lacks an insertion detection mechanism, and
there is no standard method to communicate either source or sink
capabilities
• USB Battery Charging Specifications define a method for a USB port to
advertise that additional current is available using D+/D- pins, but the upper
limit is not well defined
• It is no practical method to “guess” a device’s power consumption since the
amount of current sunk is entirely dependent upon the device
• Some USB-powered gadgets only draw Vbus and completely ignore D+/D-
• To avoid over-current conditions, the only method of budgeting
power for Standard A USB ports is to account for maximum power
consumption!
November 17 – 18, 2015
USB Implementers Forum © 2015
20
USB Developer Days 2015
November 17 – 18, 2015
USB Implementers Forum © 2015
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USB Developer Days 2015
Power Policy
• System Power Policy is the manufacturer’s decision, but having a
more flexible approach may give a better user experience
• Wide-range voltage input enables charging from more sources
• Accepting power from a source that does not provide sufficient power to
actually charge the system may still extend system runtime
• Devices that do this are available on the market today!
• Prioritize Power based on Intended Use
• Example: When attached to an external power source, a Hub with a built-in
Battery may determine the Sink Capabilities of the Host to better decide how
to charge its internal battery while still supplying power
November 17 – 18, 2015
USB Implementers Forum © 2015
22
USB Developer Days 2015
Power Policy in Action
Accepts:
Minimum
20V @ 3A
C
C
PD
November 17 – 18, 2015
Provides:
5V @ 3A
12V @ 3A
20V @ 3A
USB Implementers Forum © 2015
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USB Developer Days 2015
Power Policy in Action
Needs 2.5W,
Advertises:
5V @ 2.5A
12V @ 2.79A
20V @ 2.87A
Required
Minimum:
20V @ 3A
Rejects
20V @ 2.87A
C
Mini
Dock
HDMI

Standard Display
C
C
PD
November 17 – 18, 2015
Provides:
5V @ 3A
12V @ 3A
20V @ 3A
USB Implementers Forum © 2015
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USB Developer Days 2015
Power Policy in Action
Needs 8W,
Advertises:
5V @ 1.4A
12V @ 2.3A
Required
Minimum:
5V @ 1.5A
Accepts
12V @ 2.3A
C
Mini
Dock
HDMI

Standard Display
C
USB
C
PD
November 17 – 18, 2015
Provides:
5V @ 3A
12V @ 3A
USB Implementers Forum © 2015
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USB Developer Days 2015
Smart(er) Power Distribution
Gets Sink Cap
Advertises:
12V @ 1.25A
Consumes
12V @ 1.75A
Operational
Power: 15W
Accepts
12V @ 1.25A

Portable Powered Hub
C
C
PD
Out
C
In
C
C
C
November 17 – 18, 2015
Provides:
5V @ 3A
12V @ 3A
USB Implementers Forum © 2015
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USB Developer Days 2015
Practical
Charge-Through
Hubs
• Special Dual Role Ports
• Captive Cable vs Receptacle
• Re-Regulating vs Passing-Through
• Protocol Walkthrough
• Exception Handling
November 17 – 18, 2015
USB Implementers Forum © 2015
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USB Developer Days 2015
Special Dual Role Ports
• Sinking DFP
• Sub-class of a DRP that is capable of sinking power, but not capable of acting
as a device. PD Support is required for Data Role Swap.
• A PD Source can be connected to Hub’s Sinking DFP
• Charging UFP
• Sub-class of a DRP that is capable of supplying power, but not capable of
acting as a host. Operates as a device but not as a host. PD Support is
required for Data Role Swap.
• Upstream Port of a Hub that can be used to Charge a Device with a Dead Battery
November 17 – 18, 2015
USB Implementers Forum © 2015
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USB Developer Days 2015
Captive Cable vs Receptacle
• Captive Cable
• Access to Vconn
• Reduced BOM since there is no
need for a switch/mux or
electronic marker
• Receptacle
• Vconn is not passed through the
cable
• Needs to support reversibility so
signal switch is required
• Depending on functionality, may
need to source Vconn and read
electronic marker in the cable
November 17 – 18, 2015
USB Implementers Forum © 2015
29
USB Developer Days 2015
Re-Regulating vs Passing-Through
Provides:
5V @ 2.4A
9V @ 2.4A
15V @ 2A
Provides:
5V @ 2.4A
9V @ 2.4A
15V @ 2A
C
PD
Requires 3W
Advertises:
5V @ 1.8A
9V @ 2A
15V @ 1.8A
Mini
Dock
C
C
PD
Requires 3W
Advertises:
5V @ 2.4A
12V @ 2.25A
20V @ 1.35A
C
Mini
Dock
C
C
November 17 – 18, 2015
USB Implementers Forum © 2015
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USB Developer Days 2015
Protocol Walkthrough: Scenario Overview
 Connect Mini-Dock as a Bus-Powered Device
 Connect PD Adapter to Mini-Dock
 Mini-Dock establishes contracts with both the
Host and the PD Adapter
 Mini-Dock Charges the Host
C
Mini
Dock
C
C
PD
November 17 – 18, 2015
USB Implementers Forum © 2015
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USB Developer Days 2015
Protocol Walkthrough (1/4): Initial Connection
Host
VL100 Mini Dock
 Connect UFP to Host DFP
 Detect Rd on CC
 Turn on Vbus (5v), Rp = 1.5A
 Turn on Vconn
 Send Source_Capabilities Message
<Powered by the Host>

 Evaluate Source_Capabilities
  Request (5V @ 1.5A)
 Accept

 PS_RDY

<Explicit Contract Established>
<Explicit Contract Established>
November 17 – 18, 2015
USB Implementers Forum © 2015
32
USB Developer Days 2015
Protocol Walkthrough (2/4): Connect PD Adapter
Host
VL100 Mini-Dock
PD Adapter
<Explicit Contract with VL100;
Sourcing 5V @ 1.5A>
 Connect to Sinking DFP
 Detect Rd on CC
 Turn on Vbus (5V)
Rp = 3A
<Simultaneously Powered by
both Host and PD Adapter>

 Send Source_Capabilities

 Accept

 PS_RDY
 Evaluate Source_Capabilities
 Request (5V @ 3.0A)
<Explicit Contract Established>

<Explicit Contract Established>
November 17 – 18, 2015
USB Implementers Forum © 2015
33
USB Developer Days 2015
Protocol Walkthrough (3/4): Power Role Swap
Host
VL100 Mini-Dock
PD Adapter
<Explicit Contract with VL100;
Sourcing 5V @ 1.5A>
<Simultaneously Powered by
both Host and PD Adapter>
<Explicit Contract with VL100;
Sourcing 5V @ 3.0A>

 Accept

 Turns off Vbus
 Transitions to Sink,
Presents Rd
 PS_RDY
<Implicit Contract with VL100>
 PR_Swap
<Powered by PD Adapter Only>


 PS_RDY
 Turn on Vbus (5V),
Presents Rp @ 900mA
<PD Adapter Powering both
VL100 Mini-Dock and Host>
<Power Role Swap Complete>

 Send Source_Capabilities*
* = Derived from PD Adapter
November 17 – 18, 2015
USB Implementers Forum © 2015
34
USB Developer Days 2015
Protocol Walkthrough (4/4): Charge-Through!
Host
VL100 Mini-Dock
PD Adapter
<Implicit Contract with VL100>
<Implicit Contract with Host; Source>
<Explicit Contract with PD Adapter>
<Explicit Contract with VL100;
Sourcing 5V @ 3A>
 Evaluate Source_Capabilities
 Request (20V @ 2.5A)


 Wait
 Request (20V @ 3A)


 Request


 Accept
<Updated Explicit Contract with PD
Adapter>
<Explicit Contract with VL100>
 Accept

 PS_RDY


PS_RDY
 Turn On Vbus (20V)
<Updated Explicit Contract with
VL100>
<Explicit Contracts with Host and PD
Adapter>
November 17 – 18, 2015
USB Implementers Forum © 2015
35
USB Developer Days 2015
Corner Case: Dead Battery
:(
 Host Battery is Depleted, Presents Rd
 If Mini-Dock is a standard UFP, it won’t be able
to provide power!
C
Mini
Dock
C
C
PD
November 17 – 18, 2015
USB Implementers Forum © 2015
36
USB Developer Days 2015
Corner Case: Dead Battery
:(
 Host Battery is Depleted, Presents Rd
 A Mini-Dock with Charging UFP works!
 After Host is sufficiently charged, it can
establish an Explicit PD Contract for more
power, and initiate a DR_Swap
C
Mini
Dock
C
C
PD
November 17 – 18, 2015
USB Implementers Forum © 2015
37
USB Developer Days 2015
Disaster Scenario Overview
 PD Adapter is powering Mini-Dock and Host
 PD Adapter is Disconnected!
Mini
Dock
HDMI
C
C
USB
C
PD
November 17 – 18, 2015
USB Implementers Forum © 2015
38
USB Developer Days 2015
How Long Can You Survive Without Power?
November 17 – 18, 2015
USB Implementers Forum © 2015
39
USB Developer Days 2015
I Will Survive!
Vconn_Swap!
It’s a
Lifesaver!
November 17 – 18, 2015
USB Implementers Forum © 2015
40
USB Developer Days 2015
Key Takeaways
• Topics Covered:
• USB-C Docking vs Traditional USB Docking
• Consider USB-C not necessarily as a connector that will replace everything, but rather,
it’s the first connector that offers high speed data transfer, native video, and higher
power chargers.
• Power Budgeting Basics
• Self-Powered vs Bus-Powered
• For Legacy-A Ports, Maximum Power Should Be Allocated
• A Flexible Power Policy that’s more accepting of Chargers might provide a better user
experience
• Support Get_Sink_Cap so Chargers can more intelligently distribute power
• Protocol Walkthrough
• Consider the Order of Events
• Consider Unexpected Disconnect Cases
November 17 – 18, 2015
USB Implementers Forum © 2015
41
USB Developer Days 2015
Q&A Session
November 17 – 18, 2015
USB Implementers Forum © 2015
42
USB Developer Days 2015
Backup Materials
November 17 – 18, 2015
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43
USB Developer Days 2015
Bus-Powered  Self-Powered
• Assumption: PD-Capable USB-C Port UFP, DC Jack
• Conceptual Flow:
1. Device’s UFP is connected to Host’s DFP, Establishes Explicit Contract
2. DC Power Supply is connected to Device’s DC Jack
a.
At this point, the Device is Self-Powered
3. Device can send updated Request message to re-negotiate a new Contract
to reflect this change eg, Operating Current = 100 mA
a.
Consider maintaining a minimal Contract (or utilizing Vconn if available) since the user
can still disconnect the DC Supply…
C
DC Supply
November 17 – 18, 2015
USB Implementers Forum © 2015
44
USB Developer Days 2015
“Where there is great power there
is great responsibility, where there
is less power there is less
responsibility, and where there is
no power there can, I think, be no
responsibility.”
—Winston Churchill, 1906
November 17 – 18, 2015
USB Implementers Forum © 2015
45
USB Developer Days 2015
VL100 Multiple USB-C™ Applications
• USB-IF Certified (Single-Port Mode)
• MP Now!
Part Number
Description
Package
VL100-Q3
USB-C Alt-Mode Accessory w/ Captive Cable
(UFP/Charging UFP, Vconn Power Support)
32-pin QFN (5x5mm)
 Video Dongles
VL100-Q4
USB-C Charge-Through w/ Captive Cable
(Charging UFP, Sinking DFP, Vconn Power Support)
40-pin QFN (5x5mm)
 Alt-Mode Accessory w/ Charge-Through
 USB-C Accessory w/ Charge-Through
VL100R-Q4
USB-C Charge-Through w/ USB-C Receptacle
(Charging UFP, Sinking DFP)
40-pin QFN (5x5mm)
 Docking Stations
USB Implementers Forum © 2015
USB Developer Days 2015
VL100 Block Diagram
Single Chip w/ Dual USB-C™ PD Ports & Billboard
USB Implementers Forum © 2015
USB Developer Days 2015
VL100 + VL210 Multi-Function Dongle
USB Implementers Forum © 2015