How to find the right ESD Suppressors AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in ESD Suppressors
- Reverse standoff (working) voltage
- VRWM must be at or above the highest normal voltage on the line, including any overshoot or bias. If the line runs above VRWM, the device starts conducting during normal operation, adds leakage and can distort or load the signal.
- Clamping voltage
- Clamping voltage at the datasheet's specified surge or TLP current must sit below the absolute maximum rating of the pin it protects. Standoff voltage only tells you when the part stays off. Clamping voltage tells you what the protected chip actually sees during a strike.
- Line capacitance
- For USB 3.x, HDMI, Thunderbolt, PCIe and similar multi-gigabit lines, use ultra-low-capacitance parts, typically well under 1 pF per line. For low-speed GPIO, buttons and power rails, tens of pF is acceptable. Capacitance degrades signal integrity at high data rates, so a high-capacitance part can break a fast interface.
- ESD rating
- Look for an IEC 61000-4-2 rating of at least ±8 kV contact and ±15 kV air (Level 4) for user-touchable ports. This system-level standard models a person touching a connector. Component-level HBM ratings do not cover it.
- Polarity and topology
- Use unidirectional parts on lines that stay one polarity, such as DC rails and most single-ended logic. Use bidirectional parts on lines that swing both above and below ground, such as audio, RS-485 and some analog lines. A unidirectional part on a bipolar signal conducts on the negative half of the waveform and clips it.
- Package and channel count
- Match the channel count and pinout to the connector. Flow-through array packages, such as 4-channel arrays for USB or HDMI, let traces pass straight under the part. Placement close to the connector with short ground paths matters as much as the part itself. Arrays that fit the connector's pinout make that layout possible.
Brands that matter
- Littelfuse: Broad range of TVS diodes, ESD diode arrays and polymer ESD suppressors.
- Nexperia: Large catalog of small-package, low-capacitance ESD diodes for data lines.
- Semtech: Known for RClamp ultra-low-capacitance arrays aimed at high-speed interfaces.
- STMicroelectronics: Wide selection of ESD protection arrays and TVS (Transil) diodes.
- onsemi: General-purpose ESD and TVS diodes in common packages.
- Vishay: Strong in discrete TVS diodes for power rails and surge duty.
- Bourns: Offers TVS diodes, varistors and polymer ESD parts.
- Texas Instruments: Offers the TPD series of ESD protection arrays, often paired with its interface chips.
What to avoid
- Unbranded assortment kits with no part numbers or datasheets: without the datasheet you cannot check clamping voltage or capacitance.
- Metal oxide varistors on high-speed data lines: their capacitance is far too high for fast signals.
- Choosing a part by breakdown voltage alone without checking clamping voltage at the rated current.
- Unidirectional parts on signals that swing negative relative to ground.
- Generic TVS diodes on multi-gigabit lines when an ultra-low-capacitance ESD array is what the interface needs.
Questions
What is the difference between a TVS diode and an ESD protection diode?
Both are clamping diodes. Parts sold as ESD diodes are optimized for very fast, low-energy discharges and low capacitance. General TVS diodes are rated for higher-energy surges on power or slower lines, usually with more capacitance.
Can one ESD suppressor protect a whole board?
Not usefully. Protection works by diverting the strike at the point where it enters, so place a suitable part at each exposed connector line, as close to the connector as possible, with a short path to ground.