Introducing
MediaGuard™
Unrivaled HDMI and DVI Port Protection
"MediaGuard™ provides low capacitance ESD protection, electrical isolation/backdrive protection, level shifting and overcurrent protection in a single 38-pin TSSOP package."
Today’s latest digital consumer electronics devices, such as digital TVs, flat panel monitors, DVD players, set top boxes, and PCs are rapidly adopting HDMI (High Definition Multimedia Interface) and DVI (Digital Visual Interface) ports. These interfaces are designed to support the latest video standards, including HDTV at 1080p resolution. To meet the high data rates required for these resolutions, the HDMI and DVI standards transfer data at up to 1.65 GHz. At these high speeds, providing ESD protection and ensuring good signal quality can be challenging. California Micro Devices has developed a family of integrated port protection products optimized to provide ESD (electrostatic discharge) protection and improved signal integrity for HDMI and DVI ports.

Challenges for HDMI and DVI Port Protection
The challenges for HDMI port protection designers are three fold: providing adequate ESD,ensuring backdrive protection and maintaining signal integrity. HDMI and DVI consist of 4 pairs of high speed TMDS (Transition-Minimized Differential Signaling) lines as well as slower signals (DDC, Hot Plug, CEC) and a power line. ESD can strike any pin, either by direct contact through a connector, through the HDMI cable, or through the DVI to HDMI adapter. ESD failures can be annoying, such as soft errors requiring shutdown and restart, or fatal, including permanent damage to the SOC (system-on-chip).

To protect the HDMI transmitter or receiver, an ESD protection device should be inserted between the transceiver and connector as shown in Figure 1. Key features to look for in an ESD protection device include:

  • IEC61000-4-2 contact rating - should be 8kV or greater;
  • Response time – should be < 1nS;
  • Clamp/trigger voltage - as low as possible to prevent soft and hard errors;
  • Multi strike capability – should withstand many strikes without degradation.

Figure 1. HDMI Link with ESD Protection
For high speed signals such as HDMI and DVI, it is particularly important to select ESD solutions that will provide maximum data integrity and minimize impact on the line. HDMI validation requires that systems pass compliance tests for interpair skew, intrapair skew, signal eye diagrams, and time domain reflectometry tests for impedance matching.To pass these tests and maximize interoperability among systems, designers must take care to choose ESD protection solutions that provide:

  • Very low capacitance – to minimize signal distortion;
  • Tightly matched capacitance among ESD devices to minimize signal skew;
  • Low capacitance between I/O lines to minimize crosstalk;
  • High resonance point to minimize signal attenuation at fundamental and harmonic frequencies;
  • Clean layout, with equal trace lengths and minimal turns, for minimum skew and fewer reflections.

The HDMI specification places additional requirements on system designers:

  • Electrical isolation and backdrive circuits are required on all signals to protect against damage should two pins be inad- vertently connected or if two sources or two sinks are con- nected together;
  • An HDMI source is required to provide up to 55mA of current at 5V, while also limiting the current to less than 500mA;
  • Level shifting logic for non-TMDS signals is often required in practice to ensure that low voltage CMOS SOCs can communicate.
Figure 2. CM2020/2021 Layout Advantages

Introducing MediaGuard™ CM2020 and CM2021

California Micro Devices is offering the MediaGuard™ CM2020 and CM2021, the industry’s first family of port protection solutions specifically designed for HDMI and DVI applications. These devices incorporate our unique low capacitance PicoGuard™ ESD diode technology, and build upon our proven CM1213 family of 1pF ESD diode arrays that are already in use today in many HDMI and DVI platforms. As shown in figure 2, the CM2020 is a single chip port protector for the source side. The CM2021 is a single chip port protector for the sink side. Both solutions are laid out to cleanly interface to an HDMI connector.

MediaGuard™ Main Features
The new MediaGuard™ CM2020 and CM2021 offer:

  • High levels of ESD protection : 8 kV contact and 15 kV air discharge, per IEC61000-4-2) for all 12 I/O lines (8 TMDS signals plus CEC, Hot Plug and DDC pair);
  • Fast response time (sub 1nS);
  • Able to withstand >1000 strikes;
  • Very low 9V clamping voltage with equal trigger voltage.
  • TMDS channel capacitance levels:
    • 0.9pF channel input capacitance;
    • 0.05pF matching capacitance between the TMDS intra-pair
  • Very low attenuation to beyond 3GHz, with resonance frequency > 5GHz;
  • Matched pinout to HDMI connector for matched trace lengths and straight through routing, minimizing signal skew and reflections;
  • Highest integration for 40% reduction in board space vs. discrete components;
  • Electrical isolation/backdrive protection on all lines (per HDMI specification);
  • Level shifting circuits for CEC, Hot Plug and DDC lines to ensure proper voltage levels for low voltage SOCs;
  • 175mA Max. short current limit protection on 5V supply line (CM2020 only).

Fig 3. CM2020 Device Schematic
Minimizing Insertion Loss
Insertion loss contributes to signal degradation and poor data integrity, and can cause HDMI compliance eye diagram failures. ESD solutions should minimize insertion loss at the fundamental transmission frequencies (up to 1.65GHz for HDMI) as well as the lower harmonics that contribute to the signal. The capacitance, as well as the inductance, of an ESD solution defines an insertion loss curve as well as the resonance point of that curve. As shown in figure 4, as capacitance increases, the resonance point decreases, resulting in higher attenuation of the signal at lower frequencies, and potential eye diagram failures and data errors.

Fig 4. Frequency Response vs. Capacitance
As shown in figure 4, the 1pF PicoGuard™ CM1213 family exhibits very low attenuation even at the highest HDMI data rates, with a resonance point of ~4.0 GHz. The MediaGuard™ family offers even further improvement, and is designed to minimize internal inductance as well as capacitance. As can be seen in Figure 4, MediaGuard™ offers even lower attenuation than the CM1213 family, extending the resonance frequency to beyond 5 GHz, making it an ideal solution for even the highest speed HDMI and DVI solutions.

Importance of Low Capacitance and Capacitance Matching
Minimizing capacitance is important in reducing signal attenuation and data errors. As can be seen in figure 5, increased capacitance distorts the signal, causing steps, knees, and other signal distortion that can lead to HDMI compliance failure. Because the signal is affected by many system factors (board material, trace widths, the connector, etc), it is critical to minimize the capacitance of the ESD protection device to provide the widest margin for the rest of the system design.

Fig 5. How attenuation impacts data integrity
Another important factor is making sure that the capacitance is very well matched between I/O lines. Mismatched capacitance between lines can cause problems meeting the intrapair skew and eye diagram requirements for HDMI and DVI. Even with low capacitance solutions, a small difference in capacitance can have a significant impact. Figure 6 shows an example of two low capacitance devices with a difference of 2.0pF introducing >85 pS of skew. At 1.65 Gbps, HDMI compliance has a maximum skew of 90 pS, so this is a significant portion of the total budget taken up just by two ESD devices.

Fig 6. Unmatched capacitance introduces inter- and intra-pair skew
Using discrete ESD solutions makes it very difficult to achieve good matching, as the capacitance of many “low cap” ESD devices can vary widely from device to device, even from the same vendor. In some cases the range of values (typical to max) is not even specified, while in others the range can vary by over 200%! Integrated diode solutions, such as PicoGuard™ and MediaGuard™ have the advantage that all diodes are produced on the same piece of silicon, and are inherently more closely matched than discrete ESD solutions.
MediaGuard™ CM2020 MediaGuard™ CM2021   Competing Diode Arrays Discrete Rail Clamp Diodes Varistors & Polymers
Channel Capacitance 0.9 pF 0.9 pF   3 to 5 pF 3 to 5 pF < 2pF
Intrapair Capacitance Matching 0.05 pF 0.05 pF   Not Spec’d Up to 2pF Not Spec’d
ESD Protection (IEC61000-4-2 contact/air) 8kV/15kV 8kV/15kV   8kV/15kV Often Not Spec’d < 4KV to 8kV
Clamping Voltage 9 V 9 V   9-12V 9-12V 150-500V
Trigger Voltage 9V 9V   9-12V 9-12V 500-1000V
Multi Strike Capability > 1000 Strikes > 1000 Strikes   Not Specified Not Specified Degrades with Multiple Strikes
Straight-through .5mm Matched Routing Yes Yes   No No No
Number of ESD Channels 12 12   2, 4, 8 1 1
Backdrive Protection on All Lines Yes Yes   No No No
Level Shifting Circuits Integrated Integrated   No No No
Overcurrent Protection Integrated External   External External External
Table 1. HDMI Port Protection Comparison Table

MediaGuard™ Competative Advantages
The MediaGuard™ CM2020 and CM2021 offer unmatched levels of protection, signal integrity and integration. Featuring the industry’s lowest capacitance diode arrays utilizing our PicoGuard™ technology, these devices provide robust 8kV ESD protection for over 1000 strikes without degradation. The matched capacitance and optimized layout minimize signal distortion and skew, which are inherent in discrete devices. By integrating level shifting, electrical isolation/backdrive protection circuits (HDMI requirement) and overcurrent protection (HDMI requirement), the CM2020 and CM2021 provide a complete protection solution with unmatched performance
in an economical, space saving single chip.

CMD’S ASIP™ Solutions
In recent years, the number of passive and analog components used in digital consumer electronics to address protection, termination and power requirements has radically increased. This increased number of components causes several problems:

  • Space constraints
  • Increased system design and layout complexity;
  • Increased manufacturing costs associated with the placement of thousands of discrete components;
  • Reduced system reliability.

California Micro Devices’ ASIP™ solutions address these issues, by integrating multiple discrete passive and analog components into a single chip—increasing performance and reliability while reducing component count and board space. Through the industry’s most comprehensive portfolio of products for ESD protection, EMI filtering, line termination and power management, California Micro Devices offers manufacturers a single source of integrated solutions that addresses application specific requirements for digital consumer electronics.

MediaGuard™ Resources
CM2020 HDMI Transmitter Port Protection and Interface Device datasheet (PDF)
CM2021 HDMI Receiver Port Protection and Interface Device datasheet (PDF)
MediaGuard™ brochure (PDF)
MediaGuard™ Technology Presentation (PDF)
CM2020/CM2021 Product Photo
MediaGuard™ / CM2020/21 Press Release