dm00235987

AN4775
Application note
Basics and low-cost solution proposals to move from legacy
USB2.0 connector to USB Type-C™ connector with STM32 devices
Introduction
The USB Type-C™ and the Power Delivery is certainly one of the most promising
technology to simplify our daily life and to enhance our consumer and mobile user
experience.
This new reversible USB Type-C™ connector makes the plug insertion more user friendly.
The technology offers a single platform connector to carry all necessary data (including
video), and using Power Delivery protocol allows to negotiate up to 100W of power to supply
or charge equipment connecting to this USB port. Less cables, less connectors and
universal chargers are the final objective.
Natively the USB Type-C™ connector supports up to 15W (5V @ 3A) of power, extended to
100W (up to 20V @ 5A) with the optional USB Power Delivery feature.
15W of power is far enough for most of hundred of million of legacy USB powered devices
actually on the market.
This application note is a guideline to introduce this USB Type-CTM connector onto platform
to replace legacy USB2.0 connectors. It introduces some basis of the two new standards
USB Type-C™ and the USB Power Delivery.
This document proposes some schematics to replace in a simple way legacy USB2.0
connector by USB Type-C™ one on platform using USB2.0 communication.
Table 1 provides the list of products to which this application note applies.
Table 1. Applicable products
Type
Microcontrollers
March 2016
Series
STM32L0 Series
STM32L1 Series
STM32L1W Series
STM32L4 Series
STM32F0 Series
STM32F1 Series
STM32F2 Series
STM32F3 Series
STM32F4 Series
STM32F7 Series
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AN4775
1
USB Type-C™ in a nutshell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1
USB Type-C™ vocabulary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1.1
1.2
Connector pin mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.1
2
3
VBUS power options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
CC Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.1
Plug orientation/cable twist detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2
Power Capability detection and usage . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
USB power delivery 2.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1
3.2
4
Minimum mandatory feature set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Power delivery signaling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1
Packet Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.2
K-codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Negotiating Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Alternate modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1
Alternate pins re-assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2
Billboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5
Converting STM32xx USB2.0 device only to USB Type-C™ platform 16
6
Converting STM32xx USB2.0 host to USB Type-C™ platform . . . . . . 17
7
Converting legacy STM32xx USB2.0 OTG to USB Type-C™ platform 18
8
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
9
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
10
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2/23
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Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
USB plug form factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
USB Type-C™ receptacle pinout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Pull up/down CC detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
SOP* signaling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Pins available for reconfiguration over the Full Featured Cable . . . . . . . . . . . . . . . . . . . . . 14
Pins available for reconfiguration for direct connect applications . . . . . . . . . . . . . . . . . . . . 15
Legacy device using USB Type-C™ receptacle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Legacy host using USB Type-C™ receptacle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Legacy OTG using USB Type-C™ receptacle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
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Table 1.
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
4/23
Applicable products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
USB Type-C™ receptacle pinout meaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Power supply options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
DFP CC termination (Rp) requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
UFP CC Termination (Rd) Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Voltage on Sink CC pins (Multiple Source Current Advertisements) . . . . . . . . . . . . . . . . . 11
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
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USB Type-C™ in a nutshell
USB Type-C™ in a nutshell
The USB Implementers Forum (USB-IF) introduces two complementary specifications:

The USB Power Delivery (PD) specification rev2.0 details how a link can be
transformed from a 4.5W power source (900mA at 5V on VBUS) to a 100W power or
consumer source (up to 5A at 20V).

The USB Type-C™ cable and connector specification rev1.1 details a reversible, slim
connector system based on high speed USB2.0 signals and two SuperSpeed lanes at
up to 10 Gbps, which can also be used to support Alternate Modes.
The new connector is designed to be non-polarized and fully reversible, no matter which
way it is inserted.
As such, this new reversible 24-pin USB Type-C™ plug is aimed to be an universal
connector with all the advanced features proposed by Power Delivery:

negotiating power roles,

negotiating power sourcing and consumption levels,

performing active cable identification,

exchanging vendor specific sideband messaging,

performing Alternate Mode negotiation,
allowing third-party communication protocols to be routed onto the reconfigurable pins of the
USB Type-C™ cable.
Figure 1. USB plug form factors
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USB Type-C™ in a nutshell
AN4775
The USB Type-C™ cables use the same male connector on both ends.
It is also important to mention that USB Type-C™ supports all prior protocols from USB2.0
onward, including the driver stack and power capability.
The new connector is quite small as it is only 8.4mm wide by 2.6mm high.
As depicted in Figure 1, the new USB Type-C™ plug allows to have single connector to
cover all features provided by previous plugs which improve USB facility usage for all
customers because of its flexibility in data and power role.
USB Type-C™ connection allows port to be in host-mode only, device-mode only or dual
role and both data and power roles can be independently and dynamically swapped using
USB Power Delivery commands.
1.1
USB Type-C™ vocabulary
The terminology commonly used for USB Type-C™ system is:

Downstream Facing Port (DFP): Associated with the flow of data in a USB
connection. Typically the ports on a host or on a hub to which devices are connected.
In its initial state, the DFP sources VBUS and VCONN and supports data.
A charge only DFP port only sources VBUS

Upstream Facing Port (UFP): Associated with the flow of data in a USB connection.
The port on a device or a hub that connects to a host or the DFP of a hub. In its initial
state, UFP sinks VBUS and supports data.

Dual Role Port (DRP): Refers to a USB port that can operate as either a source or a
sink. The role of the port offers may be fixed to either source or sink or may alternate
between the two port states.
Initially when operating as a source, the port also takes role of a DFP and when
operating as a sink, the port takes a role of a UFP. The port role may be change
dynamically either to reverse power or data roles.
1.1.1

Source: Port asserting Rp (Pull up resistor. See Figure 3) on CC (Command Control
pins. See Chapter 2) pins and providing power over VBUS (5V to 20V and up to 5A),
most commonly a Host or Hub DFP (like legacy Type-A port)

Sink: Port asserting Rd (Pull down resistor. See Figure 3) on CC pins and consuming
power from VBUS (5V to 20V and up to 5A), most commonly a device (like legacy TypeB port)
Minimum mandatory feature set
USB Type-C™ port are not required to implement and supports all of the advanced features
that are defined within all specifications.
The minimum features which need to be supported by the system are:
6/23

Cable attach and detach detection

Plug orientation/cable twist detection

USB2.0 connection
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1.2
USB Type-C™ in a nutshell
Connector pin mapping
The 24-pins USB Type-C™ includes


symmetric connections:
–
USB2.0 differential pairs (D+/D-)
–
Power pins: VBUS/GND
asymmetric connections
–
Two sets of Tx/Rx signal paths which support USB3.1 data speed
–
configuration channels (CC lines) which handles discovery, configuration and
management of USB Type-C™ power delivery features
–
Two Side Band Use (SBU lines) signals are present for analog audio modes and
may be used by alternate mode
Figure 2. USB Type-C™ receptacle pinout
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USB Type-C™ in a nutshell
1.2.1
AN4775
VBUS power options
Table 1. USB Type-C™ receptacle pinout meaning
Pin
Name
A1
GND
A2
TX1+
A3
TX1-
A4
VBUS
A5
CC1 or VCONN
A6
D+
A7
D-
A8
SBU1
Side Band Use
Alternate mode only
A9
VBUS
Bus power
max power is 100W split into 4 pins
A10
RX2-
A11
RX2+
USB3.0 datalines or Alternate
10Gb RX differential pair in USB3.1
A12
GND
Ground return
can be up to 5A split into 4 pins
B1
GND
Ground return
can be up to 5A split into 4 pins
B2
TX2+
B3
TX2-
USB3.0 datalines or Alternate
10Gb TX differential pair in USB3.1
B4
VBUS
Bus power
max power is 100W split into 4 pins
B5
CC2 or VCONN
Configuration Channel or power for active
or electronically marked cable
In VCONN configuration, min power is 1W
B6
D+
B7
D-
B8
SBU2
Side Band Use
Alternate mode only
B9
VBUS
Bus power
max power is 100W split into 4 pins
B10
RX1-
B11
RX1+
USB3.0 datalines or Alternate
10Gb RX differential pair in USB3.1
B12
GND
Ground return
can be up to 5A split into 4 pins
8/23
Description
Comment
Ground return
can be up to 5A split into 4 pins
USB3.0 datalines or Alternate
10Gb TX differential pair in USB3.1
Bus power
max power is 100W (20V - 5A) split into 4
pins
Configuration Channel or power for active
or electronically marked cable
In VCONN configuration, min power is 1W
USB2.0 datalines
USB2.0 datalines
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USB Type-C™ in a nutshell
VBUS provides a path to deliver power between a host and a device and between a charger
and a host/device.
Power options available from a perspective of a device with a USB Type-C™ connector are
listed below.
Table 2. Power supply options
Mode of Operation
Nominal Voltage
Maximum current
USB2.0
5V
500mA
USB3.1
5V
900mA
USB BC1.2
5V
up to 1.5A
USB Type-C™
[email protected]
5V
1.5A
USB Type-C™
[email protected]
5V
3A
USB PD
Up to 20V
up to 5A
Note
Default current based on
specification
Legacy charging
Support high power
devices
Directional control and
power level management
Remark: USB Type-C™ to Type-C cable assembly needs VBUS to be protected against 30V
DC at cable rated current (3A or 5A).
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CC Pins
2
AN4775
CC Pins
There are two CC pins in receptacle but only one CC pin is connected in cable per plug
facing port.
On both CC1 and CC2, DFP must have Rp pull up resistors, whereas UFP must have Rd
pull down resistors.
Electronic cables need to provide impedance Ra to ground on VCONN
2.1
Plug orientation/cable twist detection
As USB Type-CTM can be inserted in the receptacle in either orientation, it is mandatory to
first detect the orientation.
The detection is done thru CC lines using Rp/Rd resistors.
Initially a DFP exposes Rp terminations on its CC pins and a UFP exposes Rd terminations
on its CC pins.
To detect the connection, the DFP monitor both CC pins.
Figure 3. Pull up/down CC detection
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2.2
CC Pins
Power Capability detection and usage
USB Type-C™ power has initially two main power options: 1.5A and 3A on top on default
USB standard.
Current supply capability of the port to the device depends on Rp pull up resistor value on
DFP.
5A capability can be negotiated using USB Power Delivery protocol.
Table 3 below shows the different possible values.
Table 3. DFP CC termination (Rp) requirements
VBUS power
Current Source to
1.7V - 5.5V
Rp pull up to
4.75V - 5.5V
Rp pull up to
3.3V +/-5%
Default USB power
80A +/- 20%
56k+/- 20%(1)
36k+/- 20%
1.5A @5V
180A +/- 8%
22k+/- 5%
12k+/- 5%
3.0A @5V
330A +/- 8%
10k+/- 5%
4.7k+/- 5%
1. For Rp when implemented in the USB Type-C™ plug on a USB Type-C™ to USB 3.1 Standard-A Cable
Assembly, a USB Type-C™ to USB 2.0 Standard-A Cable Assembly, a USB Type-C™ to USB 2.0 MicroB Receptacle Adapter Assembly or a USB Type-C™ captive cable connected to a USB host, a value of 56
kΩ ± 5% shall be used, in order to provide tolerance to IR drop on VBUS and GND in the cable assembly.
UFP must also implement on both CC1 and CC2 Rd pull down resistors for biasing the
detection system and to be identified as power sinker.
Table 4. UFP CC Termination (Rd) Requirements
Rd implementation
Nominal value
Can detect power
capability?
max voltage on CC pin
+/- 20% voltage clamp
1.1V
No
1.32V
+/- 20% resistor to GND
5.1k
No
2.18V
+/- 10% resistor to GND
5.1k
Yes
2.04V
UFP which is able to detect power capability needs to monitor CC lines voltage accurately in
order to determine power capability of DFP.
Table 5. Voltage on Sink CC pins (Multiple Source Current Advertisements)
Detection
Min voltage (V)
Max voltage (V)
Threshold (V)
vRa
-0.25
0.15
0.2
vRd-Connect
0.25
2.04
-
vRd-USB
0.25
0.61
0.66
vRd-1.5
0.70
1.16
1.23
vRd-3.0
1.31
2.04
-
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USB power delivery 2.0
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AN4775
USB power delivery 2.0
In USB Power Delivery, pairs of directly attached ports negotiate voltage, current and/or
direction of power and data flow over the USB cable, using the CC wire as the
communication channel using BMC coding (Biphase Mark Coding).
The mechanisms used, operate independently of other USB methods used to negotiate
power.
3.1
Power delivery signaling
All communications are done thru CC wire in half duplex with 300Kbps bit rate.
Communication consists in 32-bit 4b/5b words BMC encoded over CC wires.
3.1.1
Packet Structure
Packet format is:

Preamble: 64-bit sequence of alternating 0s and 1s to sync up with transmitter.

SOP* (start of packet) (can be SOP, SOP’ (start of packet sequence prime) or SOP”
(start of packet sequence double prime) see Figure 4)
–
SOP Packets shall be limited to PD capable DFP and UFP only
–
SOP’ Packets are used for communication with Cable Plug attached to the DFP.
–
SOP” Packets are used for communication with Cable Plug attached to the UFP.
A cable plug capable of SOP’ or SOP” communication shall only detect and
communicate with packet starting with SOP’ or SOP”.

Message data including message header which identifies type of packet and amount of
data.

CRC: Error checking.

EOP (end of packet): unique identifier.
Figure 4. SOP* signaling
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3.1.2
USB power delivery 2.0
K-codes
K-codes are special symbols provided by the 4b5b coding. They are used to signal hard
reset and cable reset and delineate packet boundaries.
3.2
Negotiating Power
DFP is initially considered as a bus master.
The protocol layer allows the power configuration to be dynamically modified.
As such, power role, data role and VCONN swap are independently possible if both ports
support dual power role functionality.
The default voltage on VBUS is always 5V and can be reconfigured up to 20V.
The default current capability is initially defined by Rp value and can be reconfigured up to
5A for an electronically marked USB PD Type-C cable.
The protocol uses start-of-packet (SOP) communications, each of which begins with an
encoded symbol called K-code.
SOP communication contains a control or data message.
The control message has a 16-bit fixed size and is used to manage data flow.
The data message size varies depending on its contents. It provides information on data
objects.
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Alternate modes
4
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Alternate modes
All the hosts and devices (except chargers) using a USB Type-C™ receptacle shall expose
a USB interface.
If the host or device optionally supports Alternate Modes:

The host and device shall use USB Power Delivery Structured Vendor Defined
Messages (Structured VDMs) to discover, configure and enter/exit modes to enable
Alternate Modes.

It’s strongly encouraged that the device provides equivalent USB functionality where
such exists for best user experience.

Where no equivalent USB functionality is implemented, the device shall provide a USB
interface exposing a USB Billboard Device Class used to provide information needed
to identify the device. A device is not required to provide a USB interface exposing a
USB Billboard Device Class for non-user facing modes (e.g., diagnostic modes).
As Alternate Modes do not traverse the USB hub topology, they shall only be used between
a directly connected host and device.
4.1
Alternate pins re-assignment
In the Figure 5 pins highlighted in yellow are the only pins that shall be reconfigured in a fullfeature cable
Figure 5. Pins available for reconfiguration over the Full Featured Cable
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Alternate modes
Figure 6 shows pins available for reconfiguration for direct connect applications. There are
three pins more than in previous figure because this configuration is not limited by the cable
wiring.
Figure 6. Pins available for reconfiguration for direct connect applications
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4.2
Billboard
The USB Billboard Device Class definition describes the methods used to communicate the
Alternate Modes supported by a Device Container to a host system.
This includes string descriptors that can be used to provide support details in a humanreadable format.
For more details, refer to USB Device Class Definition for Billboard Devices rev1.0a April
15, 2015
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Converting STM32xx USB2.0 device only to USB Type-C™ platform
5
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Converting STM32xx USB2.0 device only to USB
Type-C™ platform
A legacy device needs to present itself as UFP by having Rd pull down between CC line and
ground. It is assumed here below that legacy USB 2.0 device maximum current is needed
and therefore, it is not necessary to monitor CC lines.
Because the plug is reversible, the two couples DP/DN need to be connected to each other
as close as possible to the receptacle, before being routed to the STM32xx device.
Figure 7. Legacy device using USB Type-C™ receptacle
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Converting STM32xx USB2.0 host to USB Type-C™ platform
Converting STM32xx USB2.0 host to USB Type-C™
platform
This use case describes how to exchange a USB2.0 standard A receptacle with a USB
Type-C™ receptacle.
As the platform is designed for USB2.0, maximum current capacity is 500 mA. If higher
supply current is available in application, Rp resistors could be adjusted to advertise 1.5 A
or even 3 A.
A legacy host needs to be configured as a DFP by having Rp pull up between CC line and
5V supply.
As the plug is reversible, the two couples DP/DN need to be connected in pairs as close as
possible to the receptacle, before being routed to the STM32xx device.
Monitoring CC lines thru ADC_IN inputs allow to detect device attachment and so to provide
VBUS on connector.
Figure 8. Legacy host using USB Type-C™ receptacle
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Converting legacy STM32xx USB2.0 OTG to USB Type-C™ platform
7
AN4775
Converting legacy STM32xx USB2.0 OTG to USB
Type-C™ platform
This use case explains how to exchange USB2.0 micro-AB receptacle to USB Type-C™
receptacle.
As in this use case, the platform is designed for USB2.0, maximum current capacity is
500 mA. If higher supply current is available in application, Rp resistors could be adjusted to
advertise 1.5 A or even 3 A.
A legacy OTG platform starts to work as host or device depending on USB_ID pin
impedance to ground provided by cable.
USB Type-C™ is fully reversible so cable does not provide any information in role. Role
needs to be detected by sensing CC lines.
Figure 9. Legacy OTG using USB Type-C™ receptacle
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Converting legacy STM32xx USB2.0 OTG to USB Type-C™ platform
Proposed sequence is:
1.
GPIO connected to OTG_FS_DFP_UFP should be high and GPIO2 connected to
Switch_enable should be low to identify platform as UFP.
2.
If VBUS is detected: platform starts with USB2.0 controller acting as device.
3.
If no VBUS is detected after 200 ms minimum, OTG_FS_DFP_UFP is pulled down to be
identified as DFP thru Rp resistors and to check whether UFP is connected by
comparing ADC_IN1 and ADC_IN2 voltages versus expected threshold on CC lines.
Power switch X1 is kept disabled.
4.
If UFP connection is detected, Switch_enable is pulled up to provide VBUS on
connector and platform starts with USB2.0 controller acting as host.
Because of plug reversibility, the two couples DP/DN need to be connected by pair as close
as possible to receptacle, before to be routed to STM32xx device.
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Conclusion
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Conclusion
This application notes gives basic knowledge of USB Type-C™ and USB Power Delivery
standard.
Some simple schematics are given to help to make the jump from USB2.0 legacy connector
to USB Type-C™ connector with very few passive components.
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References
References
USB2.0
Universal Serial Bus Revision 2.0 Specification
USB3.1
Universal Serial Bus Revision 3.1 Specification
USB PD
USB Power Delivery Specification Revision 2.0, August 11, 2014
USB BC
Battery Charging Specification Revision1.2 (including errata and ECNs through March
15, 2015), March 15, 2012
USB BB
USB Device Class Definition for Billboard Devices rev1.0a April 15, 2015
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Revision history
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Revision history
Table 6. Document revision history
22/23
Date
Revision
04-Mar-2016
1
Changes
Initial release.
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