How to Systematically Construct ESD and Surge Protection Circuits for OCT While Meeting Medical EMC Standards?

Systematic protection should follow the principle of combining "external port protection" and "internal fine protection." All external interfaces (power input, data ports, control buttons) are the first line of defense. At the AC/DC power entry, a three-stage discharge path consisting of a fuse, a Metal Oxide Varistor (MOV), and a TVS diode should be constructed to handle surges of different energy levels. For all data and I/O ports, ESD protection devices compliant with the IEC61000-4-2 Level 4 standard must be selected, with their clamping voltage lower than the withstand voltage of the backend ICs. Protection devices must be placed immediately behind the connector, where the signal enters the PCB, ensuring that discharge currents are directed to the ground plane via the shortest path to prevent intrusion into the internal circuitry. Dedicated protection devices, such as the ESD5V0D3B, can be additionally installed on the power pins of critical internal chips as a final line of defense.