Design World – Power Transmission Reference Guide June 2019

(^30) DESIGN WORLD — EE NETWORK 6 • 2019 eeworldonline.com | designworldonline.com
TEST & MEASUREMENT HANDBOOK
The USB Type-C compliance
test matrix, created by the USB
Implementors Forum, indicates
a large amount of testing for
products to be certified as
compliant with the standard.
Essentially, everything but
cables must be subjected to the
Type-C test suite for compliance
purposes. If a device is “PD
enabled,” it must also pass the
PD compliance suite. There is
also an interoperability test
suite as well as several tests
specifically for power sources.

• Standards-Based Charging: For years, the USB
  Implementer’ Forum (USB-IF), which oversees the USB
  standard, has been working to globally standardize around
  USB for charging. The International Electro-Technical
  Commission (IEC) has long since formally adopted USB,
  and more recently, USB Type-C and PD.


• USB PD Multi-Port Chargers: PD 3.0 needed a way to
  communicate PDPs to multi-port chargers. The standard
  settled on two categories of charger ports—Assured-
  Capacity Ports and Shared-Capacity Ports. In the former
  case, each port is able to deliver its rated/labeled power
  capacity independent of all other ports. In the latter, each
  port is able to deliver its rated/labeled capacity depending
  on the remaining available capacity that’s shared among
  multiple ports. The total available power capacity of the
  multiple ports is indicated to the user, and all ports on the
  charger are capable of delivering the same power rating.
  So, for example, as long as one port on the charger can
  maintain 30 W, charger packaging can claim a PDP of 30 W.
  
  
  • PPS: Another outcome of the USB-IF’s efforts to create
    an international standard that uses the USB Type-C
    interconnect is the concept of PPSs. There are two usage
    models: Powering devices in use with a fixed source and
    charging of battery-powered devices. The fixed-voltage
    features were in place with PD 2.0; PD 3.0 introduces PPS,
    which attempts to make battery charging more efficient.
  
  
  
  

For power delivery to devices, the key characteristics include a

fixed-voltage supply, stable current, and the ability to handle

dynamic loads. For battery charging, the source must deliver

variable voltage and current and account for charging rate and

thermal constraints. Most battery manufacturers recommend

beginning with a constant current and gradually increasing voltage

followed by constant voltage and gradual reduction in current.

With fixed PDOs, the charger advertises its maximum

output and the sink side chooses the closest fit. Fixed-voltage

chargers are typically unable to charge quickly without generating

excessive heat. In the PPS methodology, however, the sink

“micro-manages” its own charging regime by requesting that the

Product type

USB-C

CabCon

USB-C

EPC

USB PD

USB-C

functional

USB-C IOP

USB-C

source

power

USB 3.1

and 2.0

Cable X X X

Charger &

battery pack X X X X X

Host & hub X X X X

PD host &

PD hub

X X X X X

Host

alt mode only X X X

Device X X X X

PD device X X X X

OTG

Testing required

Not compatible with USB Type-C

USB-Type testing matrix

LeCroy — Test and Measurement HB 06-19.indd 30 6/7/19 1:38 PM