How to select ESD protection devices for HMI (Human Machine Delivery) systems?

Selecting ESD protection devices for HMIs requires consideration of the operating voltage, signal speed, interface type, and required ESD level of the protected circuit. First, determine the device's reverse operating voltage, which must be greater than the maximum normal operating voltage of the protected signal line. For example, for a 5V signal line, choose a device with VRWM ≥ 5V, such as the ESD5V0D3B. Second, consider the device's clamping voltage, which determines the voltage the signal line will be pulled to during an ESD event. This should be lower than the withstand voltage of the protected chip. For high-speed signal lines, such as USB 2.0 and HDMI, low-capacitance ESD devices must be selected, typically with a capacitance value less than 1pF, such as the ESDLC5V0D3B series, to avoid affecting signal integrity. Select unidirectional or bidirectional devices based on whether the interface is unidirectional or bidirectional. Choose the package based on the mounting method, such as SOD-323, SOT-23, or DFN. Finally, select the device's electrostatic discharge capability based on the test level requirements. Typically, IEC 61000-4-2 Level 4 requires a contact discharge of 8kV; the selected device should be able to withstand the corresponding peak current. For interfaces requiring protection of multiple signal lines, such as USB D+/D-, a multi-channel ESD array, such as ESD SRVLC05-4, can be selected to save space. Eintech offers a complete ESD product line, from single-channel to multi-channel, and from general-purpose to ultra-low capacitance types, to meet the protection needs of various HMI ports.