HDMI ESD Protection Without Sacrificing Performance

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HDMI ESD Protection without Sacrificing PerformanceAdding ESD Protection to HDMI, even at 3.4GHz, Just Became Easier
ABSTRACT WHAT SPEED DOES HDMI OPERATE AT ANYWAY?The newest high-definition multimedia interface (HDMI) 1.3 HDMI's speed is referred to in many ways, making it difficult forstandard doubles the previous HDMI 1.0 - 1.2 data rate to 3.4Gbps designers to select the proper ESD protection solution. Theper differential signal pair. This increased data rate introduces newest HDMI standard, HDMI 1.3, is commonly referred to asnew challenges in implementing a solid board design with low operating at up to 10.2Gbps at 340Mpixels/s. This is an accuratecapacitance that ensures adequate signal integrity. This is description of the system operating speed, but does not describeparticularly important when executing a robust electrostatic the speed of the transition minimized differential signalingdischarge (ESD) protection solution. Adding ESD protection to (TMDS). The TMDS speed must also be considered in order toyour HDMI system design can be simplified by choosing the select an adequate ESD protection solution.proper solution. Tyco Electronics' ESD and overcurrentprotection reference layout complies with the HDMI 1.3 As described earlier, per the HDMI 1.3 specification, the systemspecification at 3.4GHz, helps meet the requirements of the IEC operates at up to 10.2Gbps at 340Mpixels/s. The key term is61000-4-2 ESD protection specification, and optimizes board "operates at up to". This simply means that the interface willspace, all of which helps minimize risk for designers. This paper change its clock rate depending on the video capabilities of theexplores the requirements and pitfalls of designing ESD connected transmitter and receiver. Thus, the higher theprotection into HDMI 1.3 systems. resolution or color depth of both connected devices the higherthe clock rate. HDMI only needs to run fast enough to pass theOVERVIEW required amount of pixels to drive the display device (monitor,Adding ESD protection to high-definition video systems raises LCD TV, etc.). For example, if a high-definition digital video discmany complex and confusing issues that can increase costs and (DVD) player and liquid crystal display (LCD) monitor aretime-to-market. Often choices are made based on what looks like operating at full 1080P with 48-bit color depth when playingan easy solution to implement; however, the simplest approach high-definition video, more information needs to be processedmay not provide adequate ESD protection performance or than if a 480i standard definition DVD is played.optimal board footprint. In other cases, what seems like the bestESD protection solution at first is later found to require multiple Table 1 shows each resolution and the corresponding number ofboard spins to ensure that adequate timing is met. Providing pixels per line and lines per frame. For each of the color depthsadequate protection has usually meant making tradeoffs listed in Table 1, there is a corresponding number of encoded bitsbetween size, ESD protection performance, and ease of that need to be transmitted for each pixel's color. The amount ofimplementation. Until now. data that needs to be sent from the HDMI transmitter to the HDMIreceiver can be explained as a relationship of these variables,The purpose of this paper is to discuss the principal cause of including the number of frames per second to update the screen.complexity in implementing robust ESD protection for HDMI 1.3 Table 2 describes this relationship:systems - operation speed - and the design criteria that must beconsidered to provide adequate protection. HDMI Data rate = X * Y * F * BWith: X = number of pixels per lineY = number of lines per frameF = frames per secondB = number of encoded bits per pixel
www.circuitprotection.comTable 1. Summary of the supported resolutions and color depths of the different HDMI versions.HDMI Version Common Supported Resolutions Supported Color Depths Possible Color1280 x 720p (Standard HDTV) 24-bit 17 Million1.0 - 1.2 1920 x 1080p (Full HDTV) 24-bit 17 Million24-bit 17 Million30-bit 1 Billion1280 x 720p 36-bit 69 Billion48-bit (Optional) 2800 Trillion24-bit 17 Million30-bit 1 Billion1.3 1920 x 1080p 36-bit 69 Billion48-bit (Optional) 2800 Trillion24-bit 17 MillionHigher Resolutions including: 30-bit 1 Billion1440p, 1600p, etc. 36-bit 69 Billion48-bit (Optional) 2800 Trillion
Table 2. Summary of data tra... [download for more]