TVS Diodes and ESD Protection Devices

A TVS diode is sized for surge energy from lightning coupling or heavy switching, rated in peak pulse power at a defined waveform. An ESD device handles fast, low energy static discharge and is built for very low capacitance so it can sit on a high speed line. Both clamp, but they are sized against different events.

Whenever the protected line swings both sides of ground: AC lines, differential pairs and most buses. A unidirectional part conducts hard on the negative half cycle and corrupts the signal. Unidirectional parts suit DC rails that never go negative in normal operation.

Above the highest voltage the line reaches in normal service, including ripple and any transients that are not faults. Too low and the part leaks or conducts during operation. Then check the clamping voltage at your actual surge current still sits below what the protected device survives.

The device sits in parallel with the signal, so its capacitance loads the line. On a high speed pair even a few picofarads visibly degrades the eye and raises return loss. That is why low capacitance ESD parts exist as a separate category, and why you should measure the eye with the part fitted.

As close to the connector as the layout allows, so the discharge is diverted before it reaches the rest of the board, with a short wide path to ground. The signal should not pass the protected chip first and then reach the device. Stray inductance in the ground path adds overshoot.

Only if its capacitance is low enough for the data rate. A general purpose TVS sized for surge energy usually has capacitance high enough to degrade a fast link noticeably. Check the capacitance against your line, and if in doubt measure the eye diagram both ways.

Often yes. Magnetics provide isolation and some common mode rejection but are not a substitute for a clamp against fast transients. Whether additional protection is needed depends on the standard you must meet and on your layout, so confirm against the requirement rather than assuming.

With a complete part number, send the part number, quantity, delivery region and the date you need it. If you are still selecting, send the port type, the normal working voltage, the standard and level you must meet and the data rate on that line.