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A relay-coil TVS diode must be reviewed with the coil turn-off waveform, switching repetition, driver limit and required release timing. The nominal coil voltage is not enough.
Direct answer
Record the highest steady coil bias and the turn-off waveform first. Then review the TVS operating range and clamp condition against the driver and the required release time. A lower clamp is not automatically the right result when the timing requirement changes.
Record the actual turn-off condition
The coil circuit, driver topology, polarity and return path define the stress. Draw the discharge loop before comparing candidate devices, and keep the stated waveform and current beside every clamp value.
| Review item | Condition to record | Why it matters |
|---|---|---|
| Continuous bias | Supply upper limit and coil operating state | VRWM must cover sustained bias |
| Turn-off pulse | Current, duration, repetition and probe point | A single event does not define repeated operation |
| Protected node | Driver rating and functional limit | Device VC and pin voltage can differ |
| Layout loop | Coil, TVS and return trace | Long paths add overshoot |
Verify clamp and release time together
The clamp path changes the current decay in the coil. Measure coil voltage, current and the relevant mechanical or controller state under the intended switching cycle.
Read VC with its current and waveform condition.
Keep repetition rate, duty cycle and ambient condition in the record.
Do not treat a TVS, a flyback diode and an RC network as interchangeable parts.
Board verification sequence
Fix the supply, coil part number and switching cycle.
Measure both the TVS terminals and the driver pin.
Run the target operating cycle and record temperature and function.
Keep the schematic, board revision and scope settings with the result.
FAQ
Does a TVS always release a relay faster than a flyback diode?
No. The result depends on the clamp path, coil parameters, supply arrangement and driver circuit. Measure it on the target circuit.
Can IPP alone approve a relay-coil TVS?
No. IPP must be read with its waveform, repetition, temperature and the actual coil energy.
Sources
Source check date: 2026-10-15. Use the complete part number, document revision, board revision, stated test conditions and board-level verification record together.
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