Tektronix DTG5000 User Manual
Application Note
HDMI Compliance and Sink Characterization Using the
DTG5000 Series Data Timing Generator
Introduction
The High Definition Multimedia Interface (HDMI) is
an emerging consumer electronics standard that is
fast gaining acceptance by manufacturers of digital
tainment pr
enter
one-cable inter
and audio content between receiver/playback
devices and display devices.
ypical r
T
boxes, DVD players, satellite r
Definition tuners as well as personal computers.
Display devices connected via HDMI include LCD
eceiver/playback devices include cable
oducts. HDMI offers an efficient
face for High Definition (HD) video
eceivers, and High
displays, plasma displays, and pr
Thanks to the simplicity of setup and the resulting
quality of the presentation, consumers are accepting
HDMI as a “must-have” item for the full HD experience.
HDMI uses the existing Digital Video Interface (DVI)
architecture and adds capability for High Definition
Audio and High-Bandwidth Digital Content Protection
(HDCP). The latter technology enables tr
protection of high-quality digital movie content.
HDCP is r
entertainment industry, which is advocating its use in
all HD consumer products.
eceiving an enthusiastic response from the
ojection units.
ue copy
DMI Compliance & Sink Characterization Using DTG5000 Series Data Timing Generator
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Application Note
Figure 1.
HDMI pixel data flow and organization from Source to Sink.
HDMI supports standard, enhanced, or HD video as
well as standard or multi-channel surround audio. The
interface offers uncompressed digital video and a
bandwidth of up to 5 gigabytes per second through
one small connector instead of several cables and
connectors as in the past. In addition, HDMI enables
communication between the video source and the
digital television (DTV). HDMI development is overseen by HDMI Founders including Sony, Hitachi,
Panasonic (Matsushita Electric Industrial), Silicon
Image, Philips, Thomson (RCA) and T
oshiba.
The HDMI Founders have stipulated that all HDMI
products must pass a battery of required compliance
tests to qualify to use the HDMI logo. This compliance
testing will ensure true interoperability and accordingly,
customer satisfaction. Today, these tests can only be
performed at an HDMI Authorized Testing Centers
TC). Pr
(A
e-compliance testing during the design and
manufacturing stages greatly increases the likelihood
of successfully passing the final compliance tests at
the ATC. Pre-compliance testing can save valuable
time and resources.
This technical brief discusses the equipment required
for pre-compliance and compliance testing to the HDMI
physical layer Compliance Test Specifications (CTS).
HDMI Technical Characteristics
HDMI uses a high-speed serial interface that is based
on transition-minimized differential signaling (TMDS)
to send data to the r
eceiver
. TMDS signals transition
between “on” and “off” states using an algorithm that
minimizes the number of transitions to avoid excessive
levels of electr
omagnetic inter
ference (EMI) on the
cable. The differential signal amplitude is +3.3 volts,
terminated in 50 Ω with 500 mV nominal amplitude
transitions (from +2.8 V to +3.3 V).
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DMI Compliance & Sink Characterization Using DTG5000 Series Data Timing Generator
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Application Note
Standard Resolution Data Rate Frequency
VGA 640 x 480 252 Mb/s 25.2 MHz
SVGA 800 x 600 400 Mb/s 40 MHz
XGA 1024 x 768 650 Mb/s 65 MHz
SXGA 1280 x 1024 1080 Mb/s 108 MHz
UXGA 1600 x 1200 1620 Mb/s 162 MHz
640 x 480p 640 x 480 252 Mb/s 25.2 MHz
720 x 480p 720 x 480 270.27 Mb/s 27.027 MHz
576p 768 x 576 270 Mb/s 27 MHz
720p 1280 x 720 742.5 Mb/s 74.25 MHz
1
080i 1920 x 1080 742.5 Mb/s 74.25 MHz
Table 1.
Display Clock
Standards and respective data rates.
The basic TMDS transmission line is made up of three
data channels and a clock channel. Data consists of
8-bit pixels (256 discrete levels) in each of three
channels (R/G/B). These are encoded into ten-bits
words using 8B/10B encoding to minimize transitions
and to remove the DC component. The signals have
rise times on the order of 100 picoseconds. A pair of
TMDS lines is used when higher data rates are needed.
Figure 1 shows the flow of pixel data from the
graphics controller or Source device to the digital
Sink receiver.
TMDS data rates range fr
om 22.5 megapixels per
second (Mpps) to 165 Mpps, equivalent to or up to
1.65 G bits per second at the maximum clock rate
of 165 MHz. The data rate depends on the display
resolution. The relationships of display resolution, bit
rate and clock frequency are shown in the Table 1.
Figure 2.
Test points for HDMI measurements.
Compliance Testing Tools and Solutions DTG5000 Series
The goal of compliance testing is to ensur
e interoperability among the many hundreds of different HDMI
devices from as many manufacturers. By conforming
to published HDMI specifications, a device manufactur
can pave the way for a new product's acceptance in
the marketplace.
esting should also ensure that the designs are robust
T
enough to withstand the harsh treatment they can
expect to receive in the real world. As new displays
become more rugged, the devices that use them will
find their way into less sheltered environments than in
the past. Therefore, new devices should be tested to
comply with standards under a variety of operating
conditions, not just “nominal” or best-case conditions.
est parameters should r
T
each out beyond the basic
limits defined in the specifications.
Figure 2 illustrates the major elements of the HDMI
transmission system: Source, Cable and Sink. The
ce signals ar
Sour
e tested at TP1 while the Sink
devices are tested at TP2. For testing cables, meas-
ements must be performed at both TP1 and TP2.
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DMI Compliance & Sink Characterization Using DTG5000 Series Data Timing Generator
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Application Note
Electrical Signals Test CTS Test ID Test Point
Source Clock and/or Data Data Eye Diagram 7-10 TP1
Clock Jitter 7-9 TP1
Clock Duty Cycle 7-8 TP1
Overshoot/Undershoot 7-5 TP1
Rise/Fall Time 7-4 TP1
I
nter-pair Skew 7-6 TP1
Data-Data Inter-pair Skew 7-6 TP1
S
ingle-ended Intra-pair Skew 7-7 TP1
Low Level Output Voltage (VL) 7-2 TP1
S
ink Jitter Tolerance 8-7 TP2
Minimum Differential Sensitivity 8-5 TP2
Intra-pair Skew 8-6 TP2
Differential Impedance 8-8 TP2
Cable Data Eye Diagram 5-3 TP1, TP2
Table 2.
Core HDMI tests.
Most HDMI product developers want to perform
pre-compliance testing; they have a clear incentive to
ensure interoperability and compatibility. While it is
recommended to perform as many tests as possible,
certain core tests are an essential part of compliance.
able 2 summarizes some of the above core tests.
T
Transmitter or Source signal characteristics can be
effectively characterized by measuring signals at test
point TP1 to ensure that they are within standard
timing, jitter and voltage margins.
The oscilloscope is of course the key platform for
observing signals at these test points. The digital
storage oscilloscopes (DSO) and digital phosphor
oscilloscopes (DPO) in the Tektronix TDS family
can be pair
ed with the TDSHT3 application softwar
e
package for HDMI work. TDSHT3 provides accurate
automated Sour
ce measur
ements for HDMI compliance,
including those summarized in Table 2. For more
information about this subject, refer to the Tektronix
application note titled Physical Layer Compliance
Testing for HDMI Using TDSHT3 HDMI Compliance
Test Software (available at wwww.tektronix.com).
This balance of this technical brief will concentrate on
the equipment and procedures for compliance and
characterization measurements on HDMI Sink devices
and cables.
HDMI Sink T
ests
Jitter Tolerance
One of the most critical characteristics of a Sink
device is its tolerance to jitter in the incoming signal.
The HDMI standard defines the limit as 0.3 x T
ter
m T
is HDMI syntax for “unit inter
BIT
val.” The test
BIT
; the
approach is straightforward: specified amounts of jitter are injected in steps into the transmitted TMDS
signal. Each step increases the jitter amount from low
to high until the sink device fails to r
ecover the signal.
The amount of jitter at which this failure occurs is
compar
ed against the published limits for compliance.
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