Short answer
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ESD = Electrostatic Discharge, a fast, high-voltage, event (or a test standard) that can zap your circuitry.
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TVS = Transient Voltage Suppressor, a component (typically a diode array) you add to clamp harmful voltage spikes—including ESD.
What you really want to know
Many TVS parts are tuned for different transients. When someone says “ESD diode,” they mean a TVS optimized for ESD pulses (very fast, relatively low energy, very low capacitance). Other TVS parts are built for surge/EFT/load-dump (slower, much higher energy), and usually have higher capacitance.
Side-by-side
| Topic | ESD (the phenomenon/test) | TVS (the part) |
|---|---|---|
| What it is | Static discharge event (or compliance test like IEC 61000-4-2) | Protection device that clamps transients (diode, array, MOV, etc.) |
| Timescale | ~1 ns rise, ~60 ns duration | Responds in picoseconds–nanoseconds (silicon TVS) |
| Energy | milli-joules (e.g., IEC 61000-4-2 uses a 150 pF/330 Ω model) | Ranges from mJ (ESD TVS) to joules+ (surge TVS) |
| Typical current | Tens of amps peak for a few tens of ns (ESD) | Chosen to survive the specific pulse (ESD, EFT, surge, load dump) |
| Key specs involved | Test levels (e.g., 8 kV contact, 15 kV air) | VRWM (standoff), VBR (breakdown), VC (clamp), IPP (peak current), CJ (capacitance), dynamic resistance |
| Where used | Occurs at connectors, cables, people touching ports | Placed at I/O and power rails to absorb/clamp the spike |
Two flavors of TVS you’ll meet
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ESD-protection TVS (a.k.a. ESD diodes)
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Built for IEC 61000-4-2 ESD strikes.
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Ultra-low capacitance (often <1 pF) to protect high-speed lines (USB 3.x, HDMI, PCIe, RF).
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Handles very fast edges; low energy.
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Surge/EFT/Load-dump TVS
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Built for IEC 61000-4-5 surge, EFT, or automotive ISO 7637/16750 load dump.
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Much higher energy handling; often higher capacitance.
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Suited for power rails, automotive battery lines, long cables.
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How to pick the right part
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What are you protecting against?
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Only ESD on a high-speed data line → ESD TVS with very low C and low VC.
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Mains/industrial surge, long cable transients, automotive battery → Surge-rated TVS (check waveform rating like 8/20 µs).
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Match voltage: Choose VRWM at/above your line’s max operating voltage; check VC is below the IC’s absolute max.
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Capacitance matters: High-speed differential pairs need ≤0.5–1 pF devices; power lines can tolerate more.
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Uni vs. bi-directional:
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Unidirectional for DC/asymmetric lines (e.g., 5 V rails).
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Bidirectional for AC-coupled/differential signals (USB D+/D-, HDMI, RF).
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Dynamic resistance (Rd): Lower Rd ⇒ tighter clamping at a given current.
Layout tips (big impact!)
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Place the TVS as close to the connector as possible.
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Keep the path from connector pin → TVS → ground via very short and wide; add multiple stitching vias.
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Avoid long stubs from the high-speed line to the TVS; use inline placement with minimal inductance.
Common pitfalls
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Using an ESD-only diode to stop surge/load-dump—it may pass ESD tests but fail in the field.
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Putting a high-capacitance surge TVS on USB/HDMI and wrecking signal integrity.
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Choosing VRWM too low (leakage, early conduction) or VC too high (IC still gets overstressed).
One-liner to remember
ESD is the zap; TVS is the shield. ESD-optimized TVS parts are fast and low-capacitance; surge-optimized TVS parts are beefy for big energy. Use the right shield for the right zap.
