MCPC TR-021
Safety Design Guidelinefor
USB Interface for Charging
Version 2.01(E)April 25, 2019

Mobile Computing Promotion Consortium
Technology committee

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline for USB Charging Interface Version 2.01(E)Change history
Date
July 1, 2015
April 25, 2019

Version1.00(E)
2.01(E)

ChangesEnglish translation version release
English translation version for TR-021 Ver2.01

NoticeThis Guideline is the translation from Japanese version of MCPC TR-021 only for the benefit ofEnglish readers. The original Japanese version of MCPC TR-021 shall be the official specifications in
its interpretation, construction and understanding.

iCopyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Published and copyrights owned by:
Mobile Computing Promotion Consortium (MCPC)
Hasegawa Green Building,
5-12 Shiba-Koen 3-chome, Minato-ku, Tokyo, 105-0011 Japan
TEL： +81-3-5401-1935
FAX: +81-3-5401-1937
EMAIL: office@mcpc-jp.org
WEB SITE: http://www.mcpc-jp.org

Confidentiality
The MCPC Rules and the MCPC IPR Policy shall apply.

Disclaimer
This document is intended to provide standard specifications and recommended specifications, etc.
on mobile computing. Mobile Computing Promotion Consortium (hereafter MCPC) shall not be liable
for any direct, indirect or consequential damages or infringements to patents or any other rights heldby the third parties arising out of using this Specifications. This document shall not be construed to
grant (a) license(s) under any rights held by MCPC or the third parties.

How do we distinguish binary, decimal and hexadecimal numbers?
For binary numbers, we append small letter “b” (e.g. 10b)).
For binary numbers, we insert a space after every four bits. (e.g.：1000 0101 0010b).
For hexadecimal numbers, we append small letter “h” (e.g.：FFFFh and 80h).
All other numbers shall be considered to be written in decimal.

Key Words
 “May” means that something is recommended or optional at the free discretion of the vendor.
 “Should” means that although something is not essential, it is strongly recommended. W hen implementing, the vendor
shall take this requirement into consideration and determine whether this is essential or not.
 “Shall” means that something is an essential requirement. For connectivity and specificati on compliance, the featuremust be implemented, and is mandatory.

Trademark Notes
 Company names, product names, service names and the like described in this document are generally trademarked or
are registered trademarks of their respective owners.
 In general, the usage of ™ marks, © marks, and ® marks has been omitted in this document.
 In general “Inc.,” “Corporation,” “Co., Ltd.,” have been excluded from company names.

Application note
It is indicating as follows, when indicating a case of the operation on a document. :Application note :Case-of-the-operation entryii

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Table of Contents
1.

Introduction

1

2.

The case history of an accident at USB charging

2

USB Charger Functionality Outline

3

USB Charging Environment and the Scope of this Guideline
Overview on USB charging interface specification

3
6

USB charging safety design specifications

7

3.
3.1
3.2

4.

4.1 Power supply input and output parameters
4.2 Combination of Battery Charging Equipment and Cable
4.2.1
Battery Charging Equipment without bundling Cable
4.2.2
Integrated Battery Charging Equipment and Cable
4.2.3
Battery Charging Equipment and Cable connected by Proprietary Connector
4.2.4
Battery charging equipment and USB cable bundled

5.

USB charge safety design parameter list

7
8
8
8
9
9

10

5.1 Parameters common to Equipment
10
5.2 Parameters for Battery charging equipment AC power input
12
5.3 Charging Equipment DC power output parameters (Others than USBPD high-voltage
operation)
13
5.4 Charging Equipment DC power output parameters (operating at USBPD high-voltage) 16
5.5 Parameters for Cable and Connector
18
5.6 DC power input parameters
20
5.7 Built-in battery parameter21

Appendix A.

Reference specifications (Normative)

22

Appendix B.

Half short error and its counter measure examples

23

Appendix C.
Example of incorporated functionalities and reference parameters per
equipment type25
Examples of reference parameters per equipment

25

Example of parameters for high-voltage DC output

28

Example of reference parameters per cable and conversion adapter

28

iii

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)List of Tables
Table 5-1Diagram 51 Parameters common to battery charging equipment......................................11
Table 5-2 Parameters for the equipment to input power .................................................................. 12
Table 5-3 DC power output parameter (5V)...................................................................................... 15
Table 5-4 DC power output parameter (Exceeding 5V).................................................................... 17
Table 5-5 Parameters for Cable and Connector ............................................................................... 19
Table 5-6 Parameters for equipment to input DC power .................................................................. 20
Ｔable 5-7 Parameters for embedded batteries................................................................................. 21
Figure B-1 Example of output dropping characteristics.................................................................... 23
Table C-1 Reference parameters for AC adapter Accessory socket adapter .................................. 25
Table C-2 Reference parameters for accessory socket and battery charging adapter.................... 25
Table C-3 Reference parameters for mobile battery (DC input)....................................................... 26
Table C-4 Reference parameters for mobile battery (AC input) ....................................................... 26
Table C-5 Reference parameters for in-car battery charging port.................................................... 27
Table C-6 Reference parameters for Mobile smart equipment ........................................................ 27
Table C-7 Reference parameters when supplying more than 5V output to support USBPD........... 28
Table C-8 Reference parameters of a cable without USB-C connector ........................................... 28
Table C-9 Reference parameters of a cable with USB-C connector ................................................ 28
Table C-10 Reference parameters for micro B USB-C conversion adapter..................................... 29iv

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)List of Figures
Figure 3-1 Charging Equipment, Charging Cable and Equipment to be Charged............................ 4
Figure 3-2 Equipment that incorporates both of charging circuits and circuits to be charged .......... 4
Figure 3-3 Examples of USB battery charging equipment and the scope in this Document ............ 6
Figure 4-1 No bundling of battery charging cable.............................................................................. 8
Figure 4-2 In case of captive cable (1) .............................................................................................. 8
Figure 4-3 In case of captive cable (2) .............................................................................................. 9
Figure 4-4 In case USB cable bundled .............................................................................................. 9v

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline for USB Charging Interface Version 2.01(E)

1. Introduction
An USB interface is used as a power charge interface by many smaller peripherals, the Micro USB interface
especially is widely implemented for smart phones, etc. and a USB Type-C (USB-C) interface is becoming
common power charger interface.
When USB has become widely used as a charging interface, some problems have started to be recognizedin the market, such as causing a charging terminal fire and a higher temperature due to inappropriate usesby consumers or inappropriate implementations of safety circuits in the products.
This Guideline specifies the technical parameters for charging smart phones and other equipment which
support USB as a charging interface, to the improvement in charging safety, a charging terminal fire
prevention, and the heat generation control for a Micro USB interface.
This Guideline is intended to serve as the baseline for a safety design of a charging interface. The test
specifications for a safety design certification and user promotion activities for safe charging will be followed.

1

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

2. The case history of an accident at USB charging
These are the cases of accidents that occurred during USB charging.
The purpose of this document is to reduce the risk of such accidents.
i.

The half short of a charging terminal
When conductive substances (ex. metal or moisture) attach to a connector terminal, or the resulting
corrosion of the metal between connector terminals or between a connector terminal and a connector
shell generates a half-energized state, the current that flows out of them may cause heat generationand fire .
In this Guideline, the term “charging terminal” includes both the power related terminals (Vbus, GND) of
a Micro USB or USB-C connector and a connector shell.

ii.

Short-circuit of the terminals by deforming a Micro USB or USB-C connector
Inadequate handling of a connector, a charging terminal and a connector body cause them deformed
resulting short circuit.
There is a risk of generating high heart and fire when a short protection function is not implemented incharging adapter.

iii.

Connection of an out-of-spec charging adapter and charging equipment
The electrical specifications of a charging adapter and charging equipment need to be matched. The
charge cable that is specified or certified by a charging adapter and charging equipment must be used.
Use of charging adapters or cables outside the specifications may generate higher heat and fire by theshort circuit that is caused by electric mismatching or inappropriate insulation, or the impedance of acable itself.

iv.

Connecting a charging adapter without overcurrent and overvoltage protection
Charging with a charging adapter without overcurrent/overvoltage protection functions may generatehigher heat and fire, when current beyond the capability of a charging adapter flows.

v.

Smoke and Extraordinary Heat Generation of battery built-in equipment
In case that a temperature control and a discharge and charge control in an internal battery are notadequately performed or there is no safety measure in a built-in battery for a short circuit between
poles, the battery may become in an abnormal state causing smoke and extreme heat.

2

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

3. USB Charger Functionality Outline
3.1 USB Charging Environment and the Scope of this Guideline
USB interface is the specifications which USB Implementers Forum developed to data communications
by connecting host equipment (such as PC) with external devices using a cable. To connect small external
devices without an external power supply, electric power can be supplied.
With the wide adoption of the USB interface to PCs, it is now used not only as a communication interface,but also as an electric power supply interface. It serves as a common power supply interface for small
equipment such as smart phones.
Moreover, in the product market of power supply adapters and devices with a USB power supply capability,
various kinds of implementations using its environment have showed up in the market. Under such variety of
implementations, this Guideline covers the case as the most common use case at the time of publishing thisGuideline.
In this Document, the category of the applicable devices shall be defined and the mechanisms etc. foreach device shall be set out as follows;
1.

2.

3.

Battery Charging Equipment;
Equipment that supplies DC current to equipment to be charged.
In the battery charging equipment herein, electric circuit parts that supply DC current to otherequipment shall be deemed as the battery charging equipment as a matter of convenience.
In case a charging cable and charging equipment do not separate (i.e. a captive cable), thecharging cable shall be deemed as charging equipment as a matter of convenience.
Equipment to be Charged
Equipment that supplies electricity with DC current to electric circuits in the equipment
In the electric charging equipment herein, electric circuit parts that supply DC power from otherequipment to the other electric circuits in the equipment shall be deemed as equipment to be
charged.
Charging Cable;
A cable and a connector that transmit the DC current generated at charging equipment toequipment to be charged.

3

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Charging equipment (Cable integrated model)

Equipment
to be charged

Charging cable

Charging
equipment

Figure 3-1 Charging Equipment, Charging Cable and Equipment to be Charged

Equipment

Input power

Circuits fortheequipmentPowersupplycircuit tointernal
units

Power
supplycircuit to an
external unit

Equipment to be charged

Output power

Charging equipment

Figure 3-2 Equipment that incorporates both of charging circuits and circuits to be charged

4

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Each category of the above equipment herein shall be defined as follows;
1
Battery charging equipment
1.1 AC Adapter --- Equipment that is linked with an AC power supply and supply DC power toequipment to be charged via a USB interface
1.2 Mobile battery --- Equipment that incorporates a battery, is intended to be carried for use andcharge DC power from a battery to equipment to be supplied via a USB interface.
That DC power supply part shall be defined as charging equipment.
1.3 Mobile smart equipment --- Equipment that incorporates a battery and is intended to be carried foruse. In case DC power supply from a battery to equipment to be supplied via a USB
interface can be made, the DC power supply part shall be defined as charging equipment.
In this document, an existence and functionalities of electric circuits that do not serve tocharge external equipment shall not limit the definition herein.
For example, a smart phone that has the functionality to supply power to external
equipment and embeds electric circuits such as communication circuits in the equipment
shall be categorized as this equipment.
1.4 Accessory socket adapter --- Equipment that is linked with a car accessory socket (or a powersocket) and supply DC power to equipment to be charged via a USB interface.
1.5 Battery charging interface for an in-car equipment --- Among in-car battery charging interfaces or
equipment, those that are for example embedded in a dashboard and are not intended to
be detached for use by users.
2
Equipment to be charged
Equipment that can be charged with DC power from external equipment to its electric circuits or battery
and is equipped with a USB interface for the power charge.
2.1 Mobile battery --- Equipment that incorporates a battery, is intended to be carried for use andcharge DC power from a battery to equipment to be supplied via a USB interface.
The power input part for power supply to the electric circuits in equipment and power
charge to a battery is categorized as the equipment to be charged.
2.2 Mobile smart device --- In the equipment where a battery is built-in and is intended to carryfor use, a DC power input part for battery charging to the equipment or to the battery
itself is categorized as the equipment to be charged.
In this document, an existence and functionalities of electric circuits that do not serve tocharge external equipment shall not limit the definition herein.
For example, a smart phone that has a battery charging functionality and embeds electric
circuits such as communication circuits in the equipment shall be categorized as thisequipment.
3
Battery Charging Cable
The ones that mount a USB micro B or USB-C connector as a DC power supply interface to equipment
to be charged. So-called conversion adapter that does not mount a cable part shall also be included in
the category.

5

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Mobile sm art equipment
Accessory socket
Battery charging adapter and in-car
equipm ent

Figure 3-3 Examples of USB battery charging equipment and the scope in this Document

3.2 Overview on USB charging interface specification
Reference specifications [BC1.2]
A dedicated charging port (“Dedicated charging port, DCP”) is a port only for charge that does not support
data communications. Power supplies without enumerations with hosts, such as an AC/DC adapter, arespecified.
Charging equipment can draw 1.5A max from DCP and is identified by the short circuit of D+ and D- terminals.
Reference Specifications (Type C1.2)
A USB-C connector is a new connector that does not have differences in top or bottom connector shapes
and host or device configuration. The battery charging parameters to Vbus were updated also. An
identification method to enable up to 3A current while maintaining the output voltage of 5V to Vbus. For theidentification, a newly defined CC pin is used.
Reference Specifications (USBPD3.0)
USB Power Delivery Revision3.0 specifications specify the parameters for supplying power via USB Vbus
pins and the parameters and protocols to provide 15W (5V/3A) or more as its supply power and 5V or moreas the output voltage to Vbus.

6

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

4. USB charging safety design specifications
4.1 Power supply input and output parameters
This parameter specifies the fundamental electric conditions over charging adapter.
The parameters do not directly enhance the safety of charges. However, they serve as important design
guidelines for the fundamental safety base.
(1) Power adapter parameter
The parameter specifies a DC power supply which is sourced from AC power.
As a prerequisite, the regulation by the Electrical Appliance and Material Safety Law ([EAMS]) shall beobserved for the parameters for AC/DC adapters.
This Guideline sets forth the recommended operating environments for safe and stable operations.
(2) USB output parameter
The parameter specifies a USB output to charging adapter.
In addition to the DCP support, this Guideline sets forth the recommended operating environments forsafe and stable operations.

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Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

4.2 Combination of Battery Charging Equipment and Cable
In the following Chapter, the combination of battery charging equipment and a cable and the measurement
points for various electrical characteristics are set forth.

4.2.1 Battery Charging Equipment without bundling Cable
USB receptacle connector (Type-A or USB-C) is mounted in a power output port of battery
charging equipment and a cable is not bundled.
Power output port (STD-A or USB-C connector)

Charging equipment

Electrical characteristics measurement point

Figure 4-1 No bundling of battery charging cable

4.2.2 Integrated Battery Charging Equipment and Cable
Battery charging equipment and a cable are integrated, and the cable is not detachable (*incase of a captive cable).

Power output connector
電力出力コネクタ

Charging equipment

Charging equipment
Cable not detachable

Figure 4-2 In case of captive cable (1)8Electrical characteristics
measurement point

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)4.2.3 Battery Charging Equipment and Cable connected by Proprietary
Connector
Power charging equipment and a cable can be separated but the connector for the battery charging
equipment and the cable is other than USB connector (Type-A or USB-C).

Power output connector
Charging equipment

Electrical characteristics
measurement point

Proprietary connector
for charging equipment

Figure 4-3 In case of captive cable (2)4.2.4 Battery charging equipment and USB cable bundled
USB receptacle connector (Type-A or USB-C) is mounted and a cable is bundled.
Charging equipment
Power output
Charging equipment

Power output connector

2
Bundled cable

Figure 4-4 In case USB cable bundled

9Electrical characteristics
measurement point

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

5. USB charge safety design parameter list
In this Chapter, equipment design is classified per functionality and the safe design parameters that are
required for each functionality are set forth.
Refer to Appendix C per type of equipment for the leading bundled functionalities and reference parameters.

5.1 Parameters common to Equipment
In this Chapter, the parameters common to battery charging equipment and equipment to be charged aredefined.

No.

Item

Specifications

CM1

Temperature rise in a
portion where a user
can touch during
normal operations

For the equipment that is expected
mainly to be installed in use, thesurface temperature of the main part ofa Charging Adapter shall be 70 ℃ or
less.

Reference / Referred spec
/ Notes[EAMS]
Applicable to the equipment
category ofch.C.1.1,C.1.2,C.1.5(Temperature rise ⊿T=40 degree max at
the ambience temperature of 30 degree
C.)

CM2

CM3

Temperature rise in a
portion where a user
can touch during
normal operation
continuously

Fire prevention

The contact points with human body foreach material of equipment that is
expected to be used for a user to carryshall be less than the following ranges
in temperature and contact duration.
■Metal・50 degree C for 1 minute, 48 degree C
for 10 minutes or 43 degree C for 8hours.
■Glass and Ceramic
・56 degree C for 1 minute, 48 degree C
for 10 minutes or 43 degree C for 8
hours■Others such as resin
・60 degree C for 1 minute, 48 degree C
for 10 minutes or 43 degree C for 8hours
The materials for equipment such as acase, cables or connectors that areused for IEC/UL60950 4.7.3.2(UL4.7.3.4) Body, Bush-V1 or more,
Cable VW1. Circuit board that mounts
power units and major materials suchas power control circuits except for theones used for FPC shall support theflame-retardant grade equivalent to V0of the UL Standard.

10[13732-1]
Refer to [TR-023]
Appendix C-1 for cautions
Applicable to the equipment
categories ofch.C.1.3,C.1.4,C.1.6[UL94][60950-1]

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)CM4

Safety considerations
for a thermally closure
environment without airflows (at DC maximum

power output)

In the state of the maximum rating
power output, ensure a safe operation
in a thermally closure environment
without air flows.

CM5

Safety measuresagainst heat retention(while equipment ischarging)

Charging equipment such as a mobile
battery in which a battery for a battery
power source to equipment to be
charged is built-in shall not become
unstable even when retaining heat
during charging the battery from theempty state to the full state.

CM6

Sharpness of an edgeof equipment

Test by a sharp edge tester[UL1439]*The specifications of a sharp edge
tester and the test procedures shallconform to UL1439.

No cut is produced that pierces of an
external detection tape with 2 layers.
Table 5-1Diagram 51 Parameters common to battery charging equipment

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Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

5.2 Parameters for Battery charging equipment AC power input
In this Chapter, the safety design parameters related to AC power input for battery equipment are defined;

No.

Item

Specifications

AC1

Rated input voltage- AC/DC adapter : AC100V/240V- Other adapter: should comply with thespecs of a connected device.

Reference / Referred
spec / Notes[EAMS]It should support up to 240V
to accommodate overseas
travel use cases.

AC2

Operating input
voltage- AC/DC adapter: 90V-264V- Other adapter: Allow ±10% margin to thespecification requirements of aconnection target.

AC3

Rated input frequency

50/60Hz[EAMS]

AC4

Insulation resistance

3 Mohm min[EAMS]

AC5

Leakage current

250 uA max at the measurement circuit of
IEC60950-1.

[60950-1]

AC6Lightning surge

Conform to IEC61000-4-5[61000-4-5]

Level-3(Normal Mode and Common
Mode)
Table 5-2 Parameters for the equipment to input power

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Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

5.3 Charging Equipment DC power output parameters (Others than USBPD
high-voltage operation)
In this Chapter, the safety design parameters in operating under BC1.2 or USB-C or USBPD at 5V output
voltage are defined.

No.

Item

OD1

Rated output Voltage(not USBPD Mode)

Specifications
Depending on the configurations ofcharging equipment and cables,
measurement points vary.

Reference / Referred
spec / Notes
Revised the upper limit ofvoltage at [TYPEC1.2]

In case of the charging equipment thathas multiple ports for a power output, ameasurement shall be made per power
supply circuit inside the charging
equipment.
■In case the configurations of charging
equipment and cables are equivalent toch.4.2.1
At the end of a receptacle connector
that is built-in within the range of a rated
output power, 4.75V - 5.5V.
USB-C■In case the configurations of charging
equipment and cables are equivalent toChapter ch.4.2.2, 4.2.3 and 4.2.4,
4.75-(0.75 x rated output
Current/3)V~5.5V within the range ofthe rated output current, at theconnector end that is connected to theequipment to be charged.

OD2

Rated output current

OD3

Overshoot in output
voltage

In case a micro B to USB-C conversion
cable or conversion adapter is bundled,
an output voltage at the connector endof the conversion cable and conversion
adapter shall also be measured.
The minimum requirements and more of
rated output current should be provided.
6.0V max in the load change environment
in the range of zero to a rated load.

13[BC1.2]
Section4.1.1(VCHG_OVRSH
T=6.0V)Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

OD4Undershoot in output
voltageV min in the load change environment in
the range of the following conditions;

4.1- (0.75 x Rated Output Current /3) Vor moreIn case however the battery charging
equipment and cables correspond to
ch.4.2.1, the value shall be 4.1 V or
more.

OD5

Overvoltage
protection

IDCP_LOW ~IDCP_MID
IDCP_MID ~IDCP_HI
definition
IDCP_LOW =0~30mA
IDCP_MID =30~100mA
IDCP_HI=100-mA~rated load
Do not exceed 9V max in the range of azero to rated load condition.

[BC1.2] Section4.4.2（VCHG_UNDSHT=4.1V)[BC1.2] Section4.1.5(VCHG_FAIL=9.0V)

For the battery charging
equipment equivalent torated output voltage as
OD1.
Applicable to an output
voltage of 5V.
OD6

Overcurrent
protection

Implement overcurrent protection.
The protection ensured within +30% max
of a rated output current is recommended.

OD7

Output short circuit
protection

Implement output short circuit
protection(s).

OD8Avoid energizing
during the openstate of a terminal

In case the configurations of thecharging equipment correspond to
ch.4.2.1 or 4.2.4 and the connector in
the charging equipment is USB-C,or the configurations of the charging
equipment and cables correspond to
ch.4.2.2 or 4.2.3 and the connector in
the equipment to be charges is USB-C.

OD9Voltage for USB-C
VCONN Terminal

In case that equipment to be charged
etc. or other units are not connected or
CC line for USB-C becomes open,
voltage shall not be output to a Vbus
terminal.
For the charging equipment in which
USB-C receptacle is mounted, thevoltage output to a CC pin terminal as
VCONN voltage shall not exceed
voltage (5.5V) as defined in the right

14[TYPEC1.2] Additional
requirements for ch.4.8.1.1
and 4.8.1.2[TYPEC1.2] Table4-4

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)OD10Protection frompower output halfshortSpecifications, when operating at thepower charging protocols (i.e. BC1.2,
USB-C and USBPD) by USB-IF as well
as at the other power charging
protocols.
■In case the configurations of charging
equipment and cables are equivalent toch.4.2.1
Protection functionality shall be
implemented to avoid smoke or fire, etc.
in time for a minute resistance occurrence
between charging terminals.
■In case the configurations of charging
equipment and cables are equivalent toch.4.2.2, 4.2.3 and 4.2.4,
If item CA1 is supported at the Cable,
this item is not mandated.
Table 5-3 DC power output parameter (5V)

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Appendix BCopyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

5.4 Charging Equipment DC power output parameters (operating at USBPD
high-voltage)
In this Chapter, the safety design parameters for DC output when operating beyond 5V in USBPD mode aredefined.

No.

Item

Specifications

OH1

Rated output voltage

Under an unloaded status at thereceptacle connector terminal that ismounted in battery charging equipment,
the rated output voltage shall be within
the range of ±5% of the USBPD setting
value.

OH2

Rated output current

OH3

Overshoot of output
voltage in load
fluctuation

OH4

Undershoot of output
voltage in load
fluctuation

Reference / Referred
spec / Notes[PD3.0] Table7-19
vSrcNew
vSrcValid

In case of transition of USBPD setting
voltage, the voltage overshoot andundershoot shall be within the range of+0.5V to -0.5V.
Rated output current shall be provided.
From zero-load to rated load condition,at the receptacle connector terminal thatis mounted in battery charging
equipment, the rated output voltage
shall be within the range of +5% of the
USBPD setting value.
■In case configurations of battery
charging equipment and cables
correspond to the ch.4.2.1,
From zero-load to rated load condition,at the receptacle connector terminal thatis mounted in battery charging
equipment, the rated output voltage
shall be within the range of -5% of the
USBPD setting value.
■In case the configurations of charging
equipment and cables are equivalent toch.4.2.2, 4.2.3 and 4.2.4,
At the connector terminals that arelinked with equipment to be charged in
the power range up to the rated output
current.
* for 3A cable
USBPD setting value -5% - (0.75 x
Rated output current / 3)V* for 5A cable
USBPD setting value -5% - (0.75 x
Rated output current / 5)V

16[PD3.0] Table7-19
vSrcNew[PD3.0] Table7-19
vSrcNewCopyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)OH5Support a CC line
operation error duringhigh-voltage
operation

OH6

Avoid energizing
during the open stateof a terminal

OH7

Voltage for USB-C
VCONN Terminal

When a USBPD communication error is
detected from equipment to be charged
during a USBPD operation exceedingan output voltage of 5V and USBPD
communications are not performed
properly, the output voltage shall be
returned to 5V or 0V.
In case the configurations for charging
equipment corresponds to ch.4.2.1 or
4.2.4, and the connector mounted to thecharging equipment is USB-C,or the configurations for charging
equipment and cables correspond to ch.
4.2.2 or 4.2.3 and the connector to be
charged is USB-C.
If there is no connection to equipment tobe charged etc. or a CC line for USB-C
becomes open, voltage shall not be
output to a Vbus terminal.
For the battery charging equipment inwhich USB-C receptacle is mounted,
the voltage output to a CC pin terminal
as VCONN voltage shall not exceed
voltage (5.5V) as defined in the rightSpecifications, when operating at thepower charging protocols (i.e. USBPD)
by USB-IF as well as at the other power
charging protocols.

[PD3.0] 2.6.1, 6.8.2,
8.3.3.24.1[TYPEC1.2] 4.5.2.2.2[TYPEC1.2] Additional
requirements for ch.4.8.1.1
and 4.8.1.2[TYPEC1.2] Table4-4

Table 5-4 DC power output parameter (Exceeding 5V)17

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

5.5 Parameters for Cable and Connector
In this Chapter, safety design parameters for cable and connector or conversion cable are defined.

No.

Item

Specifications

CA1

Half short protection
between charging
terminals

Protection functionality shall be
implemented to avoid smoke or fire, etc.
in time for a minute resistance occurrence
between charging terminals.

If USB-C plugs are mounted in bothends of the cable, the same safety
implementation shall be placed.
For a charging purpose only cable, a plugshell should not connect to GND in a
direct current mode.

CA2

Grounding for plug
shell

CA3

Support rated current
for USB-C to
TypeA/B conversion
cable

The conversion cable or the conversion
adapter in which the following item 1 or
2 configurations are used, CC pin for
USB-C shall connect Rp to 56kΩ±20%.
1. USB-C plug and Type-A plug areembedded in both ends.
2. USB-C plus and Micro B receptacle
are embedded in both ends.

CA4

Support both sides of
USB-C connector

The cable with a USB-C plug in which areversible plug is mounted shall becapable of charging power wheninserted at either side of the plug toequipment to be charged.

18

Reference / Referred
spec / Notes
Appendix B

In case a USB-C connector
is used, or a cable that
supports data
communications, this item
is optional.
[TYPEC1.2] 3.5.1, 3.5.2,
3.6.2, 4.11.1

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)CA5

Voltage drop at cableand connector■For a cable with the following
implementation, the voltage drop whenusing 3A power shall be 750 mV or less.
In case of a cable that supports 5A, thevoltage drop when using 5A power shallbe 750 mV or less.
1. Standalone cable with USB-C plugs
at the both ends
■For a cable with the implementationof the following item 2 or 3, the voltage
drop when using 1.5A power shall be
375 mV or less.
2. Conversion adapter that mounts a
Type-A or Micro B connector and a
USB-C connector
3. Standalone cable that mounts a
Type-A and micro B plug at the bothends
■In case the configuration of charging
equipment and a cable corresponds tothe ch.4.2, refer to OD1.

Table 5-5 Parameters for Cable and Connector

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Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

5.6 DC power input parameters
In this Chapter, safety design parameters when power from battery charging equipment or equipment to be
charged is input from a USB interface is defined.

No.

Item

Specifications

DC1(Reserved)

DC2

Avoid corrosion in
charging terminals

Do not output voltage to the Vbus in a
USB receptacle when the device is not in
the power source mode and a Charging
adapter or equipment etc. is notconnected.

DC3

Protection from overvoltage input

DC4

Protection from overcurrent input

When a voltage exceeding a rated value
is loaded to an input terminal, instability
shall be avoided.
The instability means not to cause
smoke or ignition, provided however thesmoke that is caused by the activationof a protection circuit may not apply tothis case.
An input power control circuit or an input
power cut-off circuit shall beincorporated to prevent exceeding rated
input current as the result of malfunctionof a normal DC power input operation orof a main circuit inside the equipment.

Reference / Referred
spec / Notes

Table 5-6 Parameters for equipment to input DC power20

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

5.7 Built-in battery parameterIn this Chapter, safety design parameters for equipment with a built-in battery are defined.

No.

Item

Specifications

BA1

Safety of battery incharging equipment

The safety check procedure as set out ineither of the following rules andregulations shall be executed for battery
charging equipment in which a battery,
as a power source to equipment to be
charged, is built-in.
- Appendix 9 of Electrical Applianceand Material Safety Act- IEC62133-2 (Execute the forced
internal short circuit test as set forthin the Chapter 7.3.9 except forpolymer battery)- UL1642
The equipment categorized as so-calledmobile batteries that is intended tosupply its battery power to equipment tobe charged shall execute the safety
checking procedure for a battery as set
out below;- Appendix 9 of Electrical Applianceand Material Safety Act

BA2

Temperature monitor
of batteries

BA3

Heat protection forembedded batteries

Temperature of the embedded batteries
in battery charging equipment as asource to equipment to be charged shallbe monitored.
In case the equipment to be charged
that incorporates batteries as a source
to equipment to be charged has
temperature in its battery exceeding theguarantee range of the operation,
charging or discharging power from thesaid battery shall be stopped.

Ｔable 5-7 Parameters for embedded batteries

21

Reference / Referred
spec / Notes[EAMS][62133-2][UL1642]

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline for USB Charging Interface Version 2.01(E)Appendix A.
[13732-1][60950-1][61000-4-5][62133-2][BC1.2][PD3.0][TYPEC1.2][UL1642][UL1439][USB2.0][USB3.1][TR-023][EAMS]

Reference specifications (Normative)

ISO13732-1 Ergonomics of the thermal environment — Methods for the assessment of
human responses to contact with surfaces — Part 1: Hot surfaces
IEC60950-1 Information technology equipment – Safety – Part 1: General requirements
IEC61000-4-5:Edition3 2014 Electromagnetic compatibility (EMC) – Part 4-5: Testing andmeasurement techniques – Surge immunity test
IEC62133-2 Edition 1.0 2017-02, Secondary cells and batteries containing alkaline or othernon-acid electrolytes – Safety requirements for portable sealed secondary cells, and forbatteries made from them, for use in portable applications – Part 2: Lithium systems
Battery Charging Specification Revision 1.2 by USB Implementers Forum
Universal Serial Bus Power Delivery Specification Revision3.0 by USB Implementers Forum
Universal Serial Bus Type-C Cable and Connector Revision1.2 by USB Implementers
Forum
UL1642 5th Edition, 2013-3, UL Standard for Safety for Lithium Batteries

Test for Sharpness of Edges on Equipment
Universal Serial Bus Specification Revision 2.0 by USB Implementers Forum
Universal Serial Bus Specification Revision 3.1 by USB Implementers ForumMCPC TR-023 Mobile Equipment Safety Design Guideline Version 2.00
Electrical Appliance and Material Safety Law

22

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Appendix B.
examplesHalf short error and its counter measure

B.1 Examples for measures in charging adapter and cable
Examples of measures effective to battery charging equipment and battery charging cables are shown
below;
Abnormal operations at a half-short-circuited error can be avoided by incorporating one or multiple
measures such as this example or equivalent measures.
- As the connector that is linked with equipment to be charged may cause danger of a fire and a skinburn, the charging equipment should implement temperature protecting functionality in order toavoid abnormal heat generation in battery charging equipment or battery charging cables.
- Ensure the electrical circuit(V-I) properties of a charging adapter to avoid an abnormal heatgeneration upon generating half short at a charging terminal,.
[Examples]- Enlarge the termination voltage for a drooping characteristic, or eliminate a drooping
characteristic.

OutputVoltage(V)Make terminal
voltage large
enoughNo dropping
characteris
tics

Output Current (A)Figure B-1 Example of output dropping characteristics(Reference) In the Chapter 7.1.4.3 and 10.2.3.2.1, the minimum voltage setting value as a USB
Power Delivery and PPS operation is set out and can be expected to operate similarly tothe terminal voltage of this dropping characteristics. Even for the battery charging
equipment that does not incorporate a USB Power Delivery and PPS functionality, theabove voltage can be used to be referred as the terminal voltage value for output dropping
characteristics as set forth herein.

-The cycle of an automatic recovery (auto-restart) after entering a short protection must be longenough to avoid a frequent activation of the protection function, or no automatic recovery is
supported.
・ When equipment to be charged is not properly connected or foreign materials are detected in23

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)connection, charging equipment shall stop its output.
Example・If the Rd resistance value to a USB-C CC pin finds that equipment to be charged is not connected oran undefined RD value (or the voltage value of a CC pin) is detected, stop the output.

B.2 Examples for measures in charging equipment- Even in case of occurrence of minute resistances in between charging terminals (especially in between
a connector power source terminal and a connector shell), s moke and fire can be prevented by
implementing the following (1) or (2) of the measures to the chargers as set forth in this Guideline. When
USB USB-C connector is implemented, they are optional.
[Example (1) of the measures]
A capacitor is mounted between a connector shell and the GND electrode of a substrate, without
directly grounding the conductive connector shell in the USB connector (receptacle) of equipment to a
GND of a substrate. In addition, it is desirable to set a capacitance value in consideration of the influence
over USB data communications.
[Example (2) of measures]
The PTC (Positive Temperature Coefficient) thermistor is mounted between a connector shell and asubstrate GND electrode without directly grounding the conductive connector shell in the USB
connector (receptacle) of equipment to GND in a substrate, When USB USB-C connector is
implemented, they are optional.

24

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Appendix C. Example of incorporated functionalities andreference parameters per equipment typeIn this Chapter, the incorporating functionalities and the reference parameters per leading equipment thatshould be referred to are set forth.
However, the necessity to refer the equivalent parameters does not apply if the equipment does notincorporate the functionalities that are not set forth in this Chapter or does not incorporate the functionalities.

Examples of reference parameters per equipment
C.1.1

AC adapter

An AC adapter means the equipment that generates DC battery power to the equipment to be charged,
using the power supply from an external AC power.
In case an DC power output supports USBPD and can supply power with voltage exceeding 5V, referto the parameters in the Chapter C.2.1 in addition to eh following parameters.
Equipment
category
AC adapter

Common toequipment
CM1,CM3~CM4,CM6

Power input
part
AC1~AC6Internal
inherent circuit

Power output
part
OD1~OD9
W hen supporting
USBPD, refer to C.2.1,
too.

Table C-1 Reference parameters for AC adapter Accessory socket adapter

C.1.2

Accessory socket adapter

An accessory socket battery charging adapter means the device to convert the DC power from anaccessory socket in a car as a source to DC battery power for equipment to be charged.
In case an DC power output supports USBPD and can supply power with voltage exceeding 5V, referto the parameters in the Chapter C.2.1 in addition to eh following parameters.
Equipment
category
Accessory
socket battery
charging
adapter

Common toequipment
CM1,CM3,CM6

Power entry
partDC3~DC4Internal
inherent circuit

Power output
part
OD1~OD9
W hen supporting
USBPD, refer to C.2.1,
too.

Table C-2 Reference parameters for accessory socket and battery charging adapter

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Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)

C.1.3

Mobile battery (DC input)

A mobile battery (DC input) means the equipment that has a built-in battery in the equipment andgenerates DC battery power for equipment to be charged, using the energy of the battery, and charges
power via a USB interface from an external DC power.
In case an DC power output supports USBPD and can supply power with voltage exceeding 5V, referto the parameters in the Chapter C.2.1 in addition to eh following parameters.
Equipment
category
Mobile battery(DC entry)

Common toequipment
CM2~CM6 (※)

Power entry
part
DC1~DC4Internal
inherent circuit
BA1~BA2

Power output
part
OD1~OD9
When supporting
USBPD, refer to C.2.1,
too.

(※) The equipment is assumed to be carried in use after battery charging from an external DC power
to an internal battery, refer to CM2 as a temperature increase parameter that is common to equipment.
In case of the equipment which is not assumed to carry for use, CM1 instead of CM2 shall be referred
to.
Table C-3 Reference parameters for mobile battery (DC input)

C.1.4

Mobile battery (AC input)

A mobile battery (AC input) means the equipment that has a built-in battery in the equipment andgenerate DC battery power for equipment to be charged, using the energy of the battery or the powerfrom an AC power source.
In case an DC power output supports USBPD and can supply power with voltage exceeding 5V, referto the parameters in the Chapter C.2.1 in addition to eh following parameters.
Equipment
category
Mobile battery(AC entry)

Common toequipment
CM2~CM6 (※)

Power entry
part
AC1~AC6Internal
inherent circuit
BA1~BA2

Equipment
category
OD1~OD9
When supporting
USBPD, refer to C.2.1,
too.

(※) The equipment is assumed to be carried for use after battery charging from AC power to an internal
battery, refer to CM2 as a temperature increase parameter that is common to equipment.
In case of the equipment which is not assumed to carry for use, CM1 instead of CM2 shall be referred
to.
Table C-4 Reference parameters for mobile battery (AC input)

26

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)C.1.5

In-car battery charging port

The in-car battery charging port means the port that is equipped in a device for a car dashboard or in a
DC output connector of a car body such as a dashboard.
The major difference from the Chapter C.1.2 is that the said device is mounted to a dashboard or a rack
or in a position where is not accessible by a user and is not assumed to be detached by a user in use.
In case an DC power output supports USBPD and can supply power with voltage exceeding 5V, referto the parameters in the Chapter C.2.1 in addition to eh following parameters.
Equipment
category
In-car battery
charging port

Common toequipment
CM1 (※)

Power entry
partDC3~DC4Internal
inherent circuit

Power output
part
OD1~OD9
When supporting
USBPD, refer to C.2.1,
too.

(Built-in to
dashboard)(※) In case the applicable devices are mounted to a dashboard or a rack, a flame retardant grade that
substantially exceeds the grade for the materials of the dashboard and rack is not required.
The parameters for heat retention is not required for these device categories as this case does not fall under
the actual use environment.
Table C-5 Reference parameters for in-car battery charging port

C.1.6

Mobile smart equipment

A mobile smart device is a generic term for a device that has a built-in battery in the device and can
supply power to the electric circuits or to the battery in the device via a USB interface from an external
DC power and of which the battery charging is not its main functionality.
There is a case in which DC power is supplied to equipment to be changed using the energy of a battery
as a source.
Equipment
category
Mobile smart
equipment

Commonequipment
CM2~CM6

toPower input part Internal
inherent circuit
DC1~DC4BA1~BA2

Power
outputpart
OD1~OD9(※)
When
supporting
USBPD, refer to C.2.1,
too.

(※) In case that power supply to an external equipment to be charged is possible.
Table C-6 Reference parameters for Mobile smart equipment

27

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Example of parameters for high-voltage DC output
C.2.1

DC output exceeding 5V to support USBPD

In case an output power to equipment to be charged in each of the device categories supplies a voltagethat exceeds 5V in referring to the USBPD specifications, the following parameters shall be additionallyreferred.
Equipment
category
USBPD power
output port
incorporated

Common toequipment

Power entry
partInternal
inherent circuit

Power output
part
OH1~OH7

Table C-7 Reference parameters when supplying more than 5V output to support USBPD

Example of reference parameters per cable and conversion adapter
C.3.1

Battery charging cable without USB -C connector

It means the cable with a Type-A plug connector and a micro B plug connector at the both ends of abattery charging cable.
Equipment
category
Battery charging
cableType-A
andMicro
B
connector
CA1,(CA2),CA5

USB-C
connector

Internal inherent
circuit

Cable

CA5

Table C-8 Reference parameters of a cable without USB-C connector

C.3.2

Battery charging cable with USB -C connector

It means the cable with a USB-C plug connector at the both ends of a battery charging cable or with aType-A plug and USB-C plug connector.
Equipment
category
Battery charging
cvableType-AMicroconnector
(CA2)

and
B

USB-C
connector
CA1,CA3~CA5

Internal inherent
circuit

Cable

CA5

Table C-9 Reference parameters of a cable with USB-C connector

C.3.3

Micro B USB-C conversion adapter

It means a cable with a micro B receptacle connector and a USB-C plug connector at both ends, or adongle integrated with the both connectors.

28

Copyright 1997-2019 Mobile Computing Promotion Consortium (MCPC)MCPC TR-021 Safety Design Guideline of USB Interface for Charging Version 2.01(E)Equipment
category

Conversion
adapter

Type-AMicroconnector
USB-C
connector
CA1

and
B

USB-C
connector

Internal inherent
circuitCable

CA3~CA5(Micro B->USB-C)

Table C-10 Reference parameters for micro B USB-C conversion adapter

29