Application of isolation transformer in USB interface circuit

Probe current voltage pin 420*4450 head diameter 5.0 over current and voltage pin

TP-IP4220CZ6 5V 0.35PF breakdown voltage 6V SOT

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Photocoupler

In the circuit diagram shown, H102 is a network isolation transformer. However, it's being misused by connecting both sides to ground. Originally, an isolation transformer is designed to separate the system from the transmission line, providing electrical isolation. When both sides of the transformer are grounded, this isolation is effectively lost. As a result, high-frequency noise or interference can still pass through the common ground path, significantly reducing the effectiveness of the isolation transformer. This setup can lead to signal distortion, data corruption, or even damage to sensitive components in the system. To maintain the intended functionality of the isolation transformer, it should be used with proper grounding practices that preserve its isolation capability.