Signal compliance testing
congatec ready for 3rd Generation of High-Speed serial bus architectures
Introduction to signal compliance testing
It is nice to think of a PCB trace as simply the ideal route that a signal takes from a transmitter to a receiver and, at low data rates, this is a reasonable concept. At the data rates new-generation serial standards operate, additional physical phenomena are affecting signal integrity and need to be taken into account. All conductors in the signal path, including circuit board traces, vias, connectors and cabling, must be taken into account as transmission line effects can create return losses and reflections that degrade signal levels, introduce skew, and add noise.
Faster transition times, shorter unit intervals (UIs), impedance mismatches and noise sources in the frequency domain, contribute more to bit error rates which means a required change in one’s view of “digital” design. Engineers need to take a fresh look at their strategies for connectivity, pattern generation, receiver-side testing, data acquisition, and analysis. Coupling these issues with evolving new standards and tighter compliance testing requirements creates a tougher job for companies to quickly get their products to market.
Across the electronics industry, serial bus standards for multiple purposes have been developed to address the needs of their markets and customers. A key objective of these standards is to enable interoperability with architectures across a wide range of products offered by a host of vendors.
Each specification defines attributes that products must comply with to meet the standard’s requirements. The specification defines electrical and mechanical parameters that need to be fulfilled. Interconnects need to not only comply with time and voltage requirements in the time domain, but also to losses in the frequency domain. The governing body issues standardized tests that products must pass in order to comply with the standard.
Having access to compliance measurements is required for the designer of cutting-edge solutions. They help to address potential design issues early in the design cycle and give confidence in design margins relative to the required specifications. With each new standard, comes a set of new requirements. Historically a design was commonly verified by doing transmitter compliance tests under the assumption that the receiver signal path would show a similar behavior. For new interfaces, the specification explicitly asks for receiver tests as well. While transmit signal quality is a simple and straight forward process, the receiver tests require different hardware and new test concepts. In order to ensure full compatibility and to provide the best quality, congatec invested in hardware and software that performs receiver testing.
1* passages taken from the Tektronix Primer:
‘The Basics of Serial Data Compliance and Validation Measurements’
2* passages taken from Agilent Technologies Serial ATA Backgrounder:
‘Thorough Characterization and Validation of Serial ATA Design’
3* passages taken from Agilent Technologies White Paper:
‘Crossing the Digital-Analog Divide’
congatec goes with Agilent Technologies
After a long and intensive selection process, congatec chose Agilent Technologies. Agilent Technologies’ offering is the best in today’s compliance measurement equipment.
Below are some of the reasons why:
- Agilent offers a fast and flexible solution for compliance test and characterization
The Agilent test automation software ‘Valiframe’ is a powerful platform for serial and multi-lane gigabit interface bus testing. It can operate in a simplified and intuitive ‘Compliance Mode’ or in ‘Expert Mode’, allowing manual parameter control which is important for characterization and debugging.
- The hardware is used worldwide for reference measurement
Certified test labs, such as Allion, Granit River Labs, Testronic Lab, etc. are using Agilent’s Transmitter Compliance Receiver and TDR test solutions. Agilent is offering test solutions that are certified for SATA-IO, PCIe SIG and USB IF and documented in Methods-of-Implementations (MOI).
- Complete jitter tolerance test for embedded and forwarded clock devices
The J-BERT N4903B is designed to match serial bus standards optimally with its differential I/Os, variable voltage levels on most outputs, built-in jitter and ISI, pattern sequencer, reference clock outputs, tunable CDR, pattern capture and bit recovery mode to analyze clock-less and non-deterministic patterns. SER/FER analysis allows jitter tolerance testing of devices using retimed loopback. A second data output with independent pattern memory and PRBS can be used as an aggressor channel for crosstalk tests, or when adding channels externally for OOB timing tests or emulation of 3-level signals or signal de-emphasis
- The industry’s highest real-time scope measurement accuracy
When you’re designing with faster signals, shrinking eyes and tighter jitter budgets mean that errors introduced by your oscilloscopes can seriously impact your measurement results. The Agilent Infiniium 90000 X-Series scopes deliver the highest measurement accuracy available by offering the following characteristics:
- True analog bandwidth to 33 GHz
- Lowest oscilloscope noise floor (2.25 mV at 50 mV/div,33 GHz)
- Lowest jitter measurement floor (100 fs)
Having the cleanest analog bandwidth and lowest noise floor available, results in better spectral analysis of transients and wide-bandwidth RF signals.
- Looking forward to 4th Generation of High-Speed serial bus architectures
The J-BERT N4903B and the DSA-X91604A are long-term investments which are configurable for today’s test and budget requirements and allow for upgrades and retrofits of all options and full speed when test needs change. With this in mind, congatec is looking forward to next generation High-Speed serial bus interfaces like thunderbolt.
- congatec cooperates with EKH - EyeKnowHow as fast and flexible partner
Detailed know-how is required for a perfect implementation of “high speed serial interfaces”. Each design is a new challenge because of higher speeds or different topologies to implement. Although following a design guide is good, it is not always possible. Sometimes it is difficult to judge where you can deviate from a design guide without generating functional issues in your design. Other times, you have to violate the design guide to be able to implement the design at all. In this case, you might want to gain back the lost margin in other areas of your design. And of course, if you have enough margins and know them, you can reduce cost/power or improve performance of your system with an optimized design implementation.
"EyeKnowHow" is a fast and flexible partner for congatec providing the know-how, simulation, and measurement resources as required.
congatec offers their know-how and equipment to customers
With the latest big investment in compliance measurements/testing, congatec offers its customers the ability to qualify their designs to meet the standard requirements of the following high-speed serial busses:
Serial ATA 1.5Gb/s, 3Gb/s and 6Gb/s
USB 2.0 and 3.0
Ethernet 10/100/1000 Mbit/s
PCI Express 1.x, 2.x and 3.x
DDR-SDRAM (DDR2 and DDR3)
In-house test Equipment
2 Ports; Bandwith 1.5 GHz; Transmission/Reflection Test
Serial Bit Error Ratio Test (BERT)
Agilent J-Bert N4903B
Data rate max. 7GB/s; Pattern Generator; Built-In Jitter Source; Error Detector
4 Channels; Bandwith 16GHz; Sample rate 80/40G Sa/s; Max Memory 2Gpts