USB

USB Testing Service

Overview

USB (Universal Serial Bus) is one of the most widely used high-speed serial communication interfaces, with broad applications in computers, consumer electronics, mobile devices, and industrial fields. As USB standards have evolved from USB 2.0 and USB 3.x to USB4, data transfer rates have increased from 480 Mbps to 40 Gbps, significantly raising the requirements for signal integrity. USB physical layer testing aims to evaluate the quality of high-speed signals during actual transmission to ensure they operate within standard specifications, thereby ensuring data stability and system reliability.

Common Devices Under Test

The main devices under test include:

USB host interfaces on motherboards and laptops
USB-C interfaces on smartphones and tablets
USB docking stations and hubs
Storage devices, such as USB flash drives and external hard drives
Peripherals, such as cameras, printers, and audio devices
USB modules in in-vehicle entertainment and charging systems

USB Test Standards

The main test standards include:

Standard	Properties
Electrical Characteristics	Such as voltage swing, signal levels, and impedance matching.
Timing Parameters	Including data setup time, hold time, and clock skew.
Signal Integrity	Such as eye diagram quality, jitter, and crosstalk.
Environmental Requirements	Considering the impact of factors like temperature, humidity, and power supply noise on testing.

Common USB Signal Integrity Physical Layer Test Items

Physical layer tests mainly include:

Test	Properties
Eye Diagram Test	To observe signal quality and eye opening margin.
Jitter Analysis	To evaluate random jitter and deterministic jitter.
Signal Swing and Rise/Fall Time Measurement	To check amplitude and transition times.
Return Loss and Insertion Loss	To assess reflection and transmission characteristics.
SSC (Spread Spectrum Clocking) Feature Test	To verify SSC performance.
Cable and Connector Quality Evaluation	To ensure interconnect reliability.
Rx Test (Receiver Tolerance Test)	To simulate stressed conditions using synthetic signal disturbances and verify receiver performance under extreme scenarios.

Commonly Used Test Instruments

Common instruments for signal integrity testing include:

Instrument	Properties
High-Speed Oscilloscope (Real-Time Oscilloscope)	Used for eye diagram analysis and jitter measurement (manufacturers include Keysight, Tektronix, Rohde & Schwarz).
BERT (Bit Error Rate Tester)	Used for receiver tolerance testing.
Pattern Generator	Generates standard test patterns.
Vector Network Analyzer (VNA)	Used for S-parameter measurements, such as insertion loss and return loss.

USB