Many industrial networks such as Controller Area Network (CAN), RS-485, RS-422, and Profibus should be able to withstand the harsh system-level transients present in end applications (from touch operations, inductive load interruptions, relay contact bounces, and / or electrostatic discharge [ESD] during lightning strikes. Meeting these requirements in design is difficult without the right tools and knowledge associated with the standards required by the design. In this blog post, I will discuss the International Electrotechnical Commission (IEC) 61000-4-2 standard, IEC 61000-4-2 ESD test setup and transient voltage suppressor (TVS) diode circuits that help protect CAN transceivers. .
The IEC 61000-4-2 ESD immunity test is a system level test that simulates the discharge process of a live operator to the end system. The characteristics of the IEC ESD test differ from those of other ESD standards during the rise time, such as the amount of energy transferred during an electric shock and the number of shocks managed during the test. IEC ESD involves two types of tests: contact discharge and air discharge. Contact ESD discharge testing is the direct release of an ESD pulse from an IEC ESD gun to the device under test (DUT). The air ESD discharge test is to move the charged ESD gun against the DUT until the air is broken down so that the ESD shock can be conducted between the ESD gun and the DUT. The IEC ESD test includes positive and negative polarity and is unlikely to give a passing score unless the two polarities are tolerated the same. Table 1 shows the IEC 61000-4-2 ESD test voltage and peak current levels.
Table 1: IEC 61000-4-2 ESD test voltage levels
This is an open level. Proprietary devices must specify this level. Special test equipment may be required if a voltage higher than the voltage shown in the table is specified.
Figure 1 depicts the basic shape of the IED ESD pulse and the timing sequence of the test pulse.
Figure 1: Current waveform of the IEC ESD pulse and the timing sequence of the test
Figure 2 shows the IED ESD immunity compliance test setup.
Figure 2: IEC ESD Compliance Test Setup
Texas Instruments (TI) is fully compliant with IEC ESD specifications. The metal plate on the ground is directly connected to the ground and is separated from the top metal plate by two 470k? resistors in series. The top of the upper ground plane is a thin insulating pad that separates the DUT from the plane. This prevents a low impedance path from being formed between the DUT and ground, allowing the DUT to absorb the full energy of the ESD shock. Finally, the IEC ESD generator and gun are in the upper right corner of the table, and both devices are directly connected to ground. The IEC ESD gun has a discharge network consisting of a 150pF capacitor and a 330Ω resistor, which is also specified in the standard.
To protect the CAN transceiver from the harsh transient voltages such as the IEC 61000-4-2 ESD mentioned above, a TVS diode can be placed on the bus lines CANH and CANL. This TVS diode acts as a clamping circuit that directs any high-energy pulses that appear to ground away from the transceiver. When selecting a diode, it is important to note that the diode is rated to the expected energy level as required by the design.
I paired TI's TCAN1042 and TCAN1051 transceivers with the CDSOT23-SM712 bidirectional TVS diode, which has ratings for IEC ESD applications and was tested to IEC ESD specifications. Figure 3 shows the TCAN10xx transceiver with TVS diodes, while Tables 2 and 3 show the test results.
Figure 3: TCAN10xx Transceiver with TVS Protection 
Table 2: TCAN10xx IEC ESD Contact Discharge and Air Discharge Test Results
To learn more about the TCAN1042 and TCAN1051 with transient voltage protection, check out TI Designs IEC 61000 ESD, EFT and Surge Protection CAN Reference Design. If you would like to learn more about any of the topics discussed in this blog post, or if you would like to discuss and introduce which interface topic, please leave a comment below.
Other resources
Download the TCAN1042 and TCAN1051 data sheets.
Download the white paper, "Simplify CAN Bus Implementation with Non-Blocking Transceivers"
Check out these videos related to EMC Test and TCAN1042 and TCAN1051 CAN Transceiver Series:
TCAN1042 radiates automotive EMC compliance testing.
TCAN1042 and TCAN1051 Automotive EMC Compliance Test Conducted Immunity Performance.
Detailed description of the TCAN1042EVM board.
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