Over­com­ing Test Chal­lenges of USB Type-C

PCQuest - - CONTENTS -

The new USB Type-C con­nec­tor sup­ports at­trac­tive fea­tures in­clud­ing low pro­file, high-speed data trans­port, ori­en­ta­tion in­de­pen­dence, so­phis­ti­cated power man­age­ment ca­pa­bil­ity and high-charg­ing cur­rent ca­pa­bil­ity. The com­bined fea­ture of­fer­ing has in­creased the con­nec­tor’s use for de­vices in mo­bile ap­pli­ca­tions such as mo­bile phones and tablets, as well as, desk­top prod­ucts and con­sumer elec­tron­ics. En­gi­neers who are de­sign­ing the Type-C con­nec­tor into their de­vices face new test chal­lenges that re­quire unique tools and tech­niques to ad­dress the many test pa­ram­e­ters and evolv­ing stan­dards as­so­ci­ated with the con­nec­tors’ ex­panded ca­pa­bil­i­ties.

This ar­ti­cle in­tro­duces the USB Type- C con­nec­tor, func­tion­al­ity it pro­vides, and new tools and tech­niques to suc­cess­fully ad­dress USB Type- C prod­uct val­i­da­tion.

The USB Type-C en­vi­ron­ment pro­vides more func­tion­al­ity for data trans­mis­sion and power op­tions. (Fig­ure 1.)The 24-pin con­nec­tor can be ro­tated 180 de­grees and still con­nect to like pins due to its sym­met­ri­cal pin con­fig­u­ra­tion, mak­ing it ‘ori­en­ta­tion in­de­pen­dent’ or easy to plug in any di­rec­tion.A closer look at the USB Type- C con­nec­tors’ de­sign and in­di­vid­ual pins, will help to demon­strate the full po­ten­tial of its ca­pa­bil­ity as well as its com­plex­ity for test.

High Speed Data

There are two ports(1&2) in the USB Type- C con­nec­tor each hav­ing two dif­fer­en­tial high speed lanes. In USB3.1 th­ese are trans­mit/re­ceive pairs and only one port is ac­tive at a time(Fig­ure 1. Ports iden­ti­fied in blue and green) In other ap­pli­ca­tions th­ese ports can be con­fig­ured to all be trans­mit, all re­ceive, or have one port with a USB3.1 link and the other port with a alt mode link. USB 3.1 data rates of 10 Gbs and TBT3 data rates of 20Gbs has been achieved. This slim, flip­pable Type- C con­nec­tor was de­signed with a fu­ture as 40 Gb­sis within reach for a two lane op­er­a­tion(for a fu-

ture ver­sion of USB for ex­am­ple), or 80Gbs com­pos­ite in one di­rec­tion be­ing pos­si­ble, say for a fu­ture ver­sion of Dis­playPort.

In ad­di­tion to the high-speed trans­mis­sion RX/TX pair, the con­nec­tor in­cludes a si­mul­ta­ne­ous link of USB 2 (D+, D-) which can be used for stan­dard USB 2 op­er­a­tions or as a sup­ple­men­tal link pro­vid­ing in­for­ma­tion for power de­liv­ery. The D+ con­nec­tions are tied to­gether, as are the D- con­nec­tions to main­tain the ori­en­ta­tion in­de­pen­dence of the con­nec­tor.

Al­ter­nate modes

Al­ter­nate modes or “guest pro­to­cols” use the trans­mit/re­ceive ( Tx/Rx) pairs for Dis­playPort, MHL or Thun­der­bolt data trans­fers mak­ing it pos­si­ble to trans­fer high-speed data, video and au­dio sig­nals in ad­di­tion to USB. The al­ter­nate modes are ne­go­ti­ated over the power de­liv­ery chan­nel and when in such a mode t the SBU1 and SBU2 pins(side band use) lines are used for con­trol pur­poses as de­fined in the those stan­dards.

Power de­liv­ery

The power pins, four for VBUSand four for GND provideup to 5 amps and 100 watts for dy­namic power and charg­ing of dif­fer­ent de­vices. The power de­liv­ery state,in­clud­ing volt­age and cur­rent lev­els, and whether provider or con­sumer, are de­ter­mined us­ing a pro­to­col over a chan­nel on the CC1/CC2pins.

Ca­ble ori­en­ta­tion and dy­namic con­fig­u­ra­tion

The CC1 and CC2 lines man­age the def­i­ni­tion of the con­nec­tor in­ter­face by pro­vid­ing three func­tions; ori­en­ta­tion con­fig­u­ra­tion man­age­ment, power pro­vi­sion to ca­ble­and com­mu­ni­ca­tion chan­nel for power de­liv­ery. CC1 and CC2 pins are used to es­tab­lish con­nec­tiv­ity be­tween a host and de­vice re­gard­less of the ori­en­ta­tion of the ca­ble. The USB Type- C con­nec­tor main­tains a host-to- de­vice log­i­cal re­la­tion­ship even though it is re­versible us­ing a sin­gle-wire ori­en­ta­tion de­tec­tion. When the ca­ble is plugged into the re­cep- tacle, the wire con­nects only one of the CC lines of the re­cep­ta­cle to ei­ther CC1 or CC2 on the other end, which de­ter­mines the ca­ble ori­en­ta­tion.

With an un­der­stand­ing of the con­nec­tors’ pin func­tions, we can be­gin to iden­tify the ar­eas where ad­di­tional tests, in­stru­ments and test fix­tures are needed.

USB Type-C test im­pli­ca­tions

Mul­ti­ple data pro­to­cols and data rates, var­i­ous power lev­els with re­versible di­rec­tion and a re­versible, flip­pable­ca­ble are all con­trib­u­tors to the need for ad­di­tional USB Type- C tests. Un­der­stand­ing the key ar­eas of USB Type- C test can help en­gi­neers to pri­or­i­tize and de­velop a suc­cess­ful test plan.

Key USB Type-C test ar­eas­in­clude:

Abil­ity to con­trol CC 1/2 load­ing (RP, RD,and RA) for power up , de­bug and test Abil­ity to com­mu­ni­cate over CC line for: Power setup:VBUS as con­sumer/provider, volt­age and cur­rent set­tings o Al­ter­nate mode (pro­to­col) con­trol o Dy­namic “host” and “de­vice” de­ter­mi­na­tion (part of Power De­liv­ery) for dual role ports Abil­ity to test the Power De­liv­ery com­mu­ni­ca­tion chan­nel, its pro­to­col and the VBUS pro­file in­clud­ing high cur­rent states.

De­bug of the PD pro­to­col is one of the big­gest chal­lenge en­gi­neers face since it re­quires ac­cess to the CC lines and the VBUS sig­nal in or­der to be prop­erly char­ac­ter­ized. USB PD has spec­i­fied volt­age/cur­rent (power) lev­els that de­vices can se­lect for op­er­a­tion mak­ing the abil­ity to test PD lev­els as de­vices ini­tial­ize very im­por­tant.

For sup­port of USB 3.1 TX test at up to 10G data rate, 14.5dB chan­nel fix­tures, with soft­ware in­te­grated Con­tin­u­ous Time Lin­ear Equal­izer (CTLE) and De­ci­sion Feed­back Equal­izer (DFE), are needed to cre­ate the proper com­pli­ance chan­nel.

The USB 3.1 spec­i­fi­ca­tion re­quires elec­tri­cal tests that rely on proper setup and anal­y­sis for ac­cept­able re­sults. Spread spec­trum clock­ing (SSC) mod­u­la­tion sig­nal is a re­quired test for USB 3.0 and 3.1 in re­gards to EMI, and will en­sure the de­vice is able to trans­mit an ac­cu­rate pro­file ac­cept­able for re­ceiver in­put. Also, the flip­pable USB Type- C ca­ble re­quires the RX/TX process to be ex­e­cuted for both ca­ble ori­en­ta­tions. It is also pre­sumed at this point that there is in­de­pen­dence in per­for­mance from the power de­liv­ery set­ting: as an - sump­tion that needs to be ver­i­fiedas.

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- - - - Au­thored by BRIAN FETZ, Se­nior Mar­ket­ing Pro­gram Man­ager Wire­less De­vices and So­lu­tions Group Keysight Tech­nolo­gies, Inc

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