Keysight Technologies HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing. Application Brief

Transcription

1 Keysight Technologies HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing Application Brief

2 Introduction High Definition Multimedia Interface (HDMI) is the digital video interface for consumer electronics applications. HDMI 2.0, developed by the HDMI Forum s Technical Working Group, is backwards compatible with earlier versions of the HDMI specification and significantly increases transmission bandwidths up to 18 Gbps. Since the transmission rate of HDMI 2.0 is almost double that of HDMI 1.4, interoperability issues due to signal quality distortions introduce new technical requirements for compliance testing of HDMI 2.0 sink and source devices. Keysight s certified HDMI 2.0 test solution covers all physical layer compliance tests including source, cable, and sink. This application brief provides an overview of HDMI 2.0, highlights the test challenges, and describes Keysight s HDMI test solution, including the M8190A/M8195A AXIe arbitrary waveform generator (AWG), N5399C HDMI electrical performance validation and compliance software, N5990A test automation software ( ValiFrame ) for HDMI compliance, and test fixtures. Application Overview The data rates needed to serve next-generation displays and video formats exceed the capability of the majority of today s HDMI chipsets. The new HDMI 2.0 specification significantly increases bandwidth and adds enhancements to support new and future market needs. New features include: Up to 18 Gbps bandwidth Up to 50/60 Hz video format supported, (2160p), which is 4 times the clarity of 1080p/60 video resolution Up to 32 audio channels for a multi-dimensional immersive audio experience Up to 1536 khz audio sample frequency for the highest audio fidelity Simultaneous delivery of dual video streams to multiple users on the same screen Simultaneous delivery of multi-stream audio to multiple users (up to 4) Support for the wide angle theatrical 21:9 video aspect ratio Dynamic synchronization of video and audio streams CEC extensions provides expanded command and control of consumer electronics devices through a single control point

3 03 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief The HDMI interface carries a number of separate signals, shown in Figure 1. Transmitter TP1 TP2 Sink (Display) Data Tx TMDS (AV Link) Data RX Ck xn PLL Channel (cable) Ck frequency = Data rate/n HDMI2.0: Data rates: 3.4 Gbs to 6 Gbs N = 40 xn PLL +5 SDA SCL DDC GND Reserved HPD CEC E-DDC (i2c) Ethernet/Audio return channel EDID HEC/ ARC +V CEC controller HDCP SCDC Figure 1. The HDMI 2.0 interface In earlier revisions of the specification, the maximum composite bit rate was 10.2 Gbs (three TMDS data lanes at 3.4 Gbs per lane); now with HDMI 2.0, the maximum composite bit rate has been increased to 17.8 Gbs (three data lanes at 5.94 Gbs). While there s no change to the cable and connector specifications, good quality cables are necessary to avoid interference with other PC peripherals such as wireless LAN adaptors, bluetooth devices, wireless keyboards, and mice. One major change to the HDMI interface is the addition of the Status Control Data Channel (SCDC). The SCDC has defined registers and control bits which are important for controlling the audio and video stream correctly. For example, HDMI 2.0 specifies that to reduce EMI a scrambling scheme is required in the TMDS data signals above 3.4 Gbps. Prior to sending scrambled TMDS data, the source device needs to set the control bit in the SCDC control register to let the sink know that the received data stream is sent in scrambled format. Another change was done in order to keep the clock rate at an acceptable ratio (HDMI 1.4 was 1/10th of the bit rate for a clock frequency of 25 MHz to 300 MHz). It was decided that the clock divider ratio be increased to 1/40th of the bit rate (6 Gbs/ 40 = 150 MHz maximum) which can easily be transferred over the cable without introducing any signal distortions. As signal frequencies increase, the connectors and cables look more and more like complex transmission lines, rather than simple devices, and engineers need to apply high speed design principles to ensure correct operation. Today s real time oscilloscopes have the high bandwidth and picosecond rise-time specifications that make high-speed data measurements straightforward, given the correct fixturing. Active effects such as timing jitter, oscillator phase noise, and amplifier linearity, and passive effects such as reflections and delay variations within the board traces, connectors, and cables assume greater importance than for lower rates.

4 04 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief Whether a product is a Blu-ray player, computer, graphics card, or any of the other many product types that use the successful HDMI interface, it must first be submitted to one of the worldwide HDMI Authorized Test Centers (ATC) for certification. Certification requirements are documented in the HDMI 2.0 Compliance Test Specification, or CTS. Specifications and compliance tests are defined by the technical workgroup of the HDMI Forum. The CTS defines the tests that must be run on one or more of the four high-speed TMDS lanes at each of the various resolution settings for both the HDMI 1.4b and HDMI 2.0 specifications. To test an HDMI transmitter, the test equipment must be connected to a Test Point Access adapter (TPA) that breaks out the test signals to a standard coaxial connector. An illustration of how HDMI signals are accessed by the measurement system is shown in Figure 2. TP1 TP1 ACQ Receptacle HDMI plug Connecting network to Oscilloscope Oscilloscope channnels Device under test Test point adapter Figure 2. Typical HDMI test point adaptor

5 05 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief It is not commonly the case that all HDMI TMDS signals can be connected to the measurement system at the same time, so the test process will likely include reconnection of signals. In addition, the results must be manipulated to remove the effects of the TPA and cabling used. The required processing functions for HDMI 2.0 are shown in Figure 3. These include fixture de-embedding for removing the effects of the fixture; impressing a cable model that is considered a worst-case acceptable cable in an HDMI system (loss vs. frequency); adding worst-case skew to either side of the differential pair (one signal at a time); and modeling the minimum equalization an HDMI receiver will have (the HDMI reference equalizer). TP1 TP2 HDMI transmitter HDMI sink HDMI plug Oscilloscope acquisition and transfer function application Test point adapter TP1 TP1 Acquisition Fixture de-embedding Worst case cable embedding Worst case skew modeled TP2 Reference equalization TP2Eq Measurements Figure 3. HDMI transmitter measurement with test point adaptor, cabling, and correction

6 06 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief Keysight Test Solution HDMI characterization can be segmented into four areas: source design and test, sink design and test, media physical layer design and evaluation, and protocol test. In each of these areas, the HDMI CTS has recommended procedures, methods, and equipment to perform these tests. In many cases, there are multiple methods, tools, or processes to get the job done. Keysight offers solutions in each area to meet your needs from the electrical physical layer to protocol as shown in Figure 4. The Keysight HDMI 2.0 test solution has been certified by the HDMI Forum as an official compliance test tool. The solution has the widest coverage for HDMI Physical layer compliance test. Certification was achieved at test events organized by the HDMI Forum. The Keysight solutions will be used at several Authorized Test Centers in the USA, China, and Korea. The measurement equipment used to address the test standards includes the Keysight E5071C ENA Option TDR, an Infiniium series oscilloscope with transmission simulation option, a ParBERT 81250A, or the new AWG M8190A/ M8195A with low jitter and high-quality output. The ParBERT and AWG support 18 Gbps physical-level testing, including 6G physical-level jitter tolerance and eye diagram, which are important in identifying IC level performance. Figure 4. Keysight HDMI test solution In addition to complete compliance tests, equipment options are available for specific test requirements.

7 07 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief Source Test The source test solution is based on Keysight s industry-performance-leading Infiniium oscilloscope family with an analog bandwidth of 13 GHz, which is mandated by the HDMI 2.0 CTS. This enables a rise time measurement of 42.5 ps. An issue with source testing is that different tests need to be run at different data rates. That is, some tests require the highest possible data rate while other tests require the lowest possible data rate. Automation software needs to know the supported data rates of your device. Then, based on this information, a test plan is constructed. In addition, for each test ID the source device must be set to a mode that outputs the correct video data rate in order to test at the correct data rate. Keysight has developed a fully automated test solution that indirectly forces the source device to output the required data rate. This is accomplished by using the VTF-501 Flex EDID board as shown in Figure 5. The Flex EDID board is offered as an accessory. Power supply Probe amps VTerm HDMI device under test Test point access fixture 8x1 DC/CEC interface Flex EDID VTerm Ck+ Ck Ck+ Probe head D0+ D+ Probe D0 head D1+ Ck D1 Probe D2+ head D2 D Probe head Dx+ Dx Dy Dy Dx, Dy: lanes not under test are terminated Figure 5. Fully automated source test solution The scope application controls the content of the Flex EDID in such a way that the source device is forced to operate at the data rate that is required for the currently executed test. This feature allows the compliance test software to run fully automated test cycles with minimal user interference. The Keysight N5399C and N5399D HDMI electrical performance validation and compliance software (EPVC) provides a complete test execution environment for validating and troubleshooting the electrical performance of HDMI 1.4 and HDMI 2.0 source devices. The software is one of the measurement tools accepted in the methods of implementation (MOI) of HDMI components already well-established through the world s HDMI Authorized Test Centers, and operates on Keysight s Infiniium oscilloscope family. Using the N5399C and N5399D software in the development and pre-compliance steps provides confidence in successful outcome for the compliance process at the HDMI ATC. Companies who use approved equipment and documented test processes may become an HDMI self-certifier.

8 08 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief Cable Assembly Test For HDMI cable and connector measurements, an accepted MOI is the use of time domain reflectometry. One MOI designed to provide measurement procedures for HDMI cable assemblies defined in the HDMI CTS for cable assemblies uses the Keysight E5071C ENA Option TDR and test fixtures as shown in Figure Ω terminations Fixture A TPA-R Cable DUT Fixture B TPA-R 50 Ω terminations Figure 6. HDMI cable assembly test setup The cable specification remains the same as for HDMI 1.4b category 2. The Keysight test solution performs all S-parameter measurements of the cable. From the S-parameters, processing software included inside the instrument calculates a stressed eye diagram as shown in Figure 7. You define your eye parameters at the input of the cable and then let the software calculate the eye opening at the end of the cable. Figure 7. HDMI eye diagram analysis One additional measurement for source and sink is the impedance test measurement. Going to higher data rates the Technical Work Group decided to mandate new impedance tests as part of the CTS. The transition points from the signals out of the source device to the cable and from the cable to the sink device must adhere to the specified impedance matching in order to guarantee device interoperability. If impedance matching is neglected signal impairments can occur due to multiple reflections in the link between the source and the sink devices. Therefore, an impedance measurement should be done for source and sink as specified in the CTS. In addition, the impedance measurement is required to be done while the source device is transmitting a signal. This is because impedance can vary dramatically when the device is turned off and turned on. Measurements include TMDS Data Eye Diagram, Intra- and Inter-Pair Skew, Differential Impedance, Far End Crosstalk and Attenuation, and Phase.

9 09 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief Sink Test Sink testing requires a source capable of generating a wide range of test patterns and the ability to add a precise amount of impairments to the output signal. The major high-speed tests are sensitivity, skew, jitter tolerance, and timing. Since HDMI 2.0 uses an incoherent design with a TMDS clock rate at 1/40 of the bit rate, this results in different jitter behavior on data and clock. Measurement accuracy is determined by the source noise floor (intrinsic jitter), and the ability to control the signal attributes such as injected jitter. The core of the Keysight HDMI sink test solution is the M8190A or M8195A arbitrary waveform generator (AWG) and the N5990A test automation software which guides you through the test procedure with detailed instructions and required system connectivity. This test solution enables independent clock and data jitter injection for accurate sink characterization. Figure 8. Example sink test setup using M8190A AWG The M8190A or M8195A AWG solution allows flexibility in generating adjustable transition times and ISI emulation. All of the jitter addition and ISI signal emulation can be factored into the waveform on-the-fly with no external equipment required. As a result, it s less expensive and easier to set up. Based on the capabilities of the sink device under test the N5990A software framework generates a test procedure that includes all required tests in order to meet the requirements set forth in the HDMI 2.0 CTS document. The resulting test protocol may be used to state the compliance with the HDMI 2.0 specification. Furthermore the sink test solution allows for margin testing to discover the design margin of your device under test.

10 10 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief The key features of the M8190A AWG solution include: AXIe form factor (2- slot module) Sample rate up to bit resolution Deep sample memory, 2G samples per channel (required for generating all of the video signals. This is important because the CTS requires that a valid video signal be generated for each video resolution. Therefore, a large sample memory is required to generate the video frames.) Supports data rates up to 6 Gb/s Flexible generation of distortions without cable emulators and TTCs Approved in Keysight MOI for HDMI 2.0 sink testing The key features of the new M8195A AWG solution include: AXIe form factor (1 slot module) Sample rate up to 65 8 bit resolution Deep sample memory, 16G samples per channel (required for generating all of the video signals. This is important because the CTS requires that a valid video signal be generated for each video resolution. Therefore, a large sample memory is required to generate the video frames.) Supports data rates up to 32 Gb/s Flexible generation of distortions without cable emulators and TTCs Will be included in the Keysight MOI for future HDMI sink testing Resources Keysight is an active member of the HDMI organization, with consistent participation in seminars and specification issues. For further resources to provide an overview of HDMI design, an understanding of the latest measurement techniques, and illustrations of design and debug approaches, go to

11 11 Keysight HDMI Test Solution Enables Comprehensive Physical Layer Compliance Testing - Application Brief mykeysight A personalized view into the information most relevant to you. Three-Year Warranty Keysight s commitment to superior product quality and lower total cost of ownership. The only test and measurement company with three-year warranty standard on all instruments, worldwide. Keysight Assurance Plans Up to five years of protection and no budgetary surprises to ensure your instruments are operating to specification so you can rely on accurate measurements. Keysight Technologies, Inc. DEKRA Certified ISO 9001:2008 Quality Management System Keysight Channel Partners Get the best of both worlds: Keysight s measurement expertise and product breadth, combined with channel partner convenience. For more information on Keysight Technologies products, applications or services, please contact your local Keysight office. The complete list is available at: Americas Canada (877) Brazil Mexico United States (800) Asia Pacific Australia China Hong Kong India Japan 0120 (421) 345 Korea Malaysia Singapore Taiwan Other AP Countries (65) Europe & Middle East Austria Belgium Finland France Germany Ireland Israel Italy Luxembourg Netherlands Russia Spain Sweden Switzerland Opt. 1 (DE) Opt. 2 (FR) Opt. 3 (IT) United Kingdom For other unlisted countries: (BP ) This information is subject to change without notice. Keysight Technologies, 2014 Published in USA, December 17, EN