Design_World_-_Internet_of_Things_Handbook_April_2020

eeworldonline.com | designworldonline.com 4 • 2020 DESIGN WORLD — EE NETWORK 21

TESTING USB4

USB4 Host

TMU

USB3 DN

Adapter

USB3 DN

USB4 Port USB4 Port Adapter

Host I/F

Adapter

Host Router

DP IN

Adapter

PCle DN

Adapter

PCle DN

Adapter

PCle Controller

DP Source

USB 2.0 Host

Enhanced

SuperSpeed Host

USB Type-C

Connector(s)

USB 2.0

Composite Cable

Downstream Facing Port

USB4/Enhanced SS Bus

Upstream Facing Port

Data Rate Host Connector Cable Connector Device

5G 10dB Std A 7. 5dB Std B 2.5dB

5G 10dB Std A 3.5dB Micro B 6.5dB

5G 6.5dB C 7dB C 6.5dB

5G 10dB Std A 3.5dB C 6.5dB

5G 6.5dB C 4dB Std B 2.5dB

5G 6.5dB C 4dB Micro B 6.5dB

10G 8.5dB Std A 6dB Std B 8.5dB

10G 8.5dB Std A 6dB Micro B 8.5dB

10G 8.5dB Std A 6dB C 8.5dB

10G 8.5dB C 6dB Std B 8.5dB

10G 8.5dB C 6dB Micro B 8.5dB

10G 8.5dB C 6dB C 8.5dB

Insertion loss budget for USB 3.2

Speed Total budget (dB) Host (dB) Cable (dB) Device (dB)

Gen2 (10G) 23 5.5 12 5.5

Gen3 (10G) 22.5 7. 5 7. 5 7. 5

Insertion loss budget for USB4

Insertion Loss Budget for USB 3.2 and USB4.

Source: USB Implementers Forum

Typical USB4 implementation

requirements as spelled out on

the USB Implementers Forum.

was only a short period between the USB4 announcement and spec
release because USB4 is based on the Thunderbolt 3 protocol.
Earlier generations of USB like USB3.2 could be implemented on
the Std A or B connectors, but USB4 must be implemented using the
Type-C connector. The USB4 physical data rate is 20 Gbps on one lane
with a requirement to run in x2 mode for a 40-Gbps bonded effective
bit rate. There are numerous high-speed standards that run much
faster. The challenge with USB4 is that the link must work with a low-
cost cable that is running as a 20bGbps x4 pipe or 80 Gbps.

THE USB4 ARCHITECTURE
What adds complexity is that a USB4 product must also implement
the lower-rate USB4 at 10 Gbps, USB 3.2 at 10 Gbps and 5 Gbps, USB