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The unidirectional or bidirectional TVS decision starts with the positive and negative voltage window at the port. A shorthand rule cannot replace a review of polarity, return path and downstream limits.
Direct answer
Draw the normal positive and negative voltage range first. Then record the transient path in each direction and verify whether the selected structure keeps the protected node within its allowed range.
Map both voltage directions
DC inputs, signal lines and cable ports have different normal and fault conditions. Record the positive peak, negative peak, duration and downstream withstand limit separately. The device structure does not remove the need to inspect the schematic, ground arrangement and abnormal states.
| Port condition | Question to answer | Selection action |
|---|---|---|
| Single-supply input | Can reverse voltage or negative transients occur? | Review forward and reverse paths |
| Bipolar signal | Does normal operation cross both polarities? | Check both voltage windows |
| Cabled port | Is the transient line-to-line or line-to-ground? | Draw the complete return path |
Read VBR and VC with conditions
A single breakdown label cannot establish equivalent clamping behavior. Keep the waveform, current, polarity, package and pinout with each candidate part number. Final approval requires target-board measurements and the approved test plan.
Pre-layout checks
Continuous bias remains inside the intended operating region.
Both transient directions respect downstream limits.
The connection to the entry point and return path is short.
The sample, document revision and board revision are traceable.
Frequently Asked Questions
Can a unidirectional TVS be selected from the DC label alone?
No. Reverse voltage and negative transient conditions must also be reviewed.
Does bidirectional mean the circuit has no polarity concern?
No. The circuit connection, ground arrangement and downstream paths still require schematic review.
Data source
Data verification date: 2026-10-13. These parameters must be used in conjunction with the complete model number, specification version, test conditions, and project verification records; the device data herein does not equate directly to conclusions regarding the complete system.
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