ESD204 surge protection for HDMI interface

alan000345

ESD204 surge protection for HDMI interface [Copy link]

 

Why do we need high surge protection for HDMI ?

Most engineers will add ESD protection to HDMI interfaces when designing, because HDMI interfaces are often exposed and are very sensitive to static electricity. However, at the same time, surge protection design is often easily overlooked, which becomes an important reason for system damage.

So what exactly is a surge, and why do we need to design protection measures against it? Broadly speaking, a surge is a phenomenon in which the voltage or current exceeds the peak value in an instant. The duration of a surge is often very short, but the energy generated by the violent pulse often has a great impact on the system.

There are many reasons for high surges in HDMI interfaces, but the main factors are long HDMI cables and lightning. The energy generated by these factors is generally greater than that generated by static electricity, so relatively speaking, better protection is needed.

Some students may wonder, for which application scenarios are HDMI interfaces more likely to face high surges caused by long cables, lightning, etc. as mentioned above? Let's take building automation monitoring as an example. IP network surveillance cameras are often installed in various areas indoors and outdoors, so they also need to be protected against long cables and lightning. Of course, we also recommend that consumer products, especially TVs, laptops, TV set-top boxes, etc., add high surge protection when designing. Imagine that in some environments, such as hotels and some private residences, people will place HDMI interfaces on the wall and run cables through the wall to the corresponding devices. So the wiring inside the wall will be relatively long. This requires surge protection to prevent consumers from using long cables to damage the HDMI interface.

IEC-61000-4-5 Standard

IEC 61000-4-5 is a standard for surge protection issued by the International Electrotechnical Commission. You can refer to the following diagram to understand the difference between the IEC standards for static electricity IEC 61000-4-2 and surge IEC 61000-4-5. Static electricity has a higher current spike, but the surge protection standard needs to deal with longer and higher energy impacts, which also requires a higher level of protection.

查看详情

Figure 1. Schematic diagram of electrostatic and surge current waveforms

Here we recommend TI's ESD204 material to cope with HDMI's high surge protection scenario. The specific introduction is as follows:

ESD204 Introduction

The ESD204 is a bidirectional TVS ESD protection diode array that provides up to 5.5A (8/20s) surge protection for HDMI and USB. The ESD204 is rated to dissipate ESD strikes to the highest level specified in the IEC 61000-4-2 (Level 4) international standard.

Performance of ESD204 in actual HDMI protection

First, we need to test whether the addition of ESD204 protection diodes will affect the signal transmission of the system. HDMI 2.0 compliance testing includes testing VL, rise time and fall time, line pair and intra-pair skew, differential voltage, clock duty cycle, clock jitter, data eye diagram and differential impedance.

The experimental results show that ESD204 passed all tests of HDMI 2.0 compliance test. Figure 2 here shows the results of the test eye diagram. We can see that ESD204 is strong enough to support maintaining HDMI signal integrity.

查看详情

Figure 2. Eye diagram test results

HDMI protection chip comparison

You may be curious about what HDMI protection chips TI has. So how can I choose a protection chip that fully meets my requirements?

Table 1 lists the three HDMI interface protection chips we recommend for your reference.

Table 1. Parameter comparison

SPEC	TPD4E02B04	ESD224	ESD204
IEC 61000-4-2	12kV Contact 15kv Air Gap	12kV Contact 15kv Air Gap	30kV Contact 30kv Air Gap
IEC 61000-4-5	2A (8/20us)	2A (8/20us)	5.5A (8/20us)
Flow Through	Yes	No	Yes
Clamping Voltage	14V at 16A TLP	8V at 16A TLP	11.5V at 16A TLP
Capacitance	0.27pF	0.50pF	0.55pF

It can be clearly seen from the above table that these three different chips have their own advantages and cover different HDMI protection scenarios.

If you have high requirements on the total capacitance of the system and need to transmit very high-speed signals, the low-capacitance TPD4E02B04 would be a good choice. In addition, the TPD4E02B04 has a DQA package, which can help you better maintain signal integrity.

Of course, the capacitance of these three chips is sufficient to meet the signal rate transmission standard required by HDMI 2.0. But if your system is very sensitive to high voltage, then ESD224 will be a good choice for you. Because ESD224 has a lower clamping voltage, it can help you clamp the system impact voltage at a lower level when surges and static electricity are generated.

As for the protagonist of this article, ESD204, we certainly recommend you to use it in higher surge scenarios. As mentioned before, long cables, lightning and other factors are potential inducing factors of high surge. ESD204 can provide 5.5A (8/20 us) protection according to the IEC61000-4-5 standard, which is your best choice for surge protection of interfaces such as HDMI!