TVS and Zener diodes may look similar in a schematic, but they are optimised for different jobs. A Zener is commonly used as a reference or clamp with a relatively small, longer-lasting current. A TVS is designed to divert short transients with high peak current.
Check these seven points
- Disturbance: ESD, inductive spike, supply surge or continuous clamping?
- Working voltage: reverse standoff voltage must allow the normal signal and tolerances.
- Breakdown and clamping voltage: check both; clamping voltage at peak current can be much higher.
- Pulse energy: compare pulse power, waveform and duration with the expected event.
- Unidirectional or bidirectional: choose for signal type and polarity.
- Capacitance and leakage: particularly important on fast data and sensitive measurement lines.
- Layout and package: a long ground path adds inductance and can reduce protection performance.
Do not simply select a TVS with the same nominal voltage as the protected circuit. Normal maximum voltage, tolerances and the permitted protected-node voltage must fit the device's working, breakdown and clamping voltages.
A TVS or Zener does not automatically make a design ESD-, surge- or automotive-ready. Also validate the layout and applicable test conditions.
View TVS diodes or Zener diodes, then verify datasheet, polarity, package and pulse-test conditions.