Protection

ESD Protection Diodes

Tiny diodes that protect your IC pins from human-body static and other transient events.

What is it?

An ESD (Electrostatic Discharge) protection diode is a low-capacitance TVS placed across a signal line and ground. During normal operation it is invisible to the signal (very low leakage, very low capacitance). When an ESD strike hits — for example a person touching a USB connector after walking across carpet — the diode breaks down and shunts the surge current to ground in nanoseconds, clamping the line to a safe voltage before it can damage the connected IC.

ESD protection diode shunting a transient to groundCONNECTORPROTECTED ICSoCESD diode(low C, fast clamp)ESD strike (±15 kV)→ shunted to GND
ESD diode placed across the signal line clamps the transient to a safe voltage and shunts current to ground before it reaches the protected IC.

When do you need it?

  • Any data line that connects to the outside world: USB 2.0 / 3.x / Type-C, HDMI, DisplayPort, Ethernet, audio jacks, antenna ports.
  • Internal high-speed buses that route past connectors or near board edges (PCIe, MIPI, LVDS).
  • Sensor lines exposed during assembly (touch panel, accelerometer breakouts, debug headers).
  • Any pin on an MCU or SoC that does NOT have on-chip ESD strong enough for IEC 61000-4-2 system-level testing (silicon HBM rating is much weaker than IEC ±15 kV).

How to pick the right one

VRWM (Reverse Working Voltage)
Must be at least the maximum DC voltage on the line. Common choices: 3.3 V, 5 V, 12 V, 24 V.
Capacitance (Cj)
Critical for high-speed signals. USB 2.0 tolerates up to ~3 pF; USB 3.x / HDMI 2.1 need <0.5 pF; PCIe Gen 4+ wants <0.3 pF. Lower is always better for signal integrity but costs more die area.
Clamping Voltage (VC)
How much voltage actually reaches the protected IC during a strike. Lower clamping = better. Snapback parts clamp to 5-7 V, conventional TVS clamps to 10-20 V.
IPP (Peak Pulse Current)
How much surge current the diode can absorb without damage, tested per IEC 61000-4-5 8/20 μs. Higher IPP = more robust against real-world surges (cable discharge events, etc.).
Channels (1-line / multi-line array)
Single-line for one signal, array (2 / 4 / 6 / 8 channels) to save board space on differential pairs or buses.
Package
DFN0603 (0201) for tightest space (USB Type-C connectors), DFN1006 (0402) most common, SOT23-3/5/6 for multi-channel arrays. Smaller package = lower parasitic inductance = better clamping.

What Magnias offers

Magnias offers a complete ESD portfolio from single-line ultra-low-capacitance (0.2 pF, e.g. PZ0502Y-F2 in DFN0603) for USB 3.x / HDMI / DisplayPort, up to multi-channel arrays for USB Type-C, Ethernet, and antenna ports. Most parts are AEC-Q101 qualified for automotive use, with snapback technology for lowest possible clamping voltage. Working voltages from 3.3 V to 24 V cover virtually every signal line you'll encounter.

Common questions

Why does ESD diode capacitance matter so much for high-speed signals?
Capacitance loads the signal line and rolls off the high-frequency content. A 3 pF diode on a USB 3.0 line will close the eye diagram noticeably; 0.3 pF is nearly invisible. Always pick the lowest capacitance your budget allows for >1 Gbps signals.
My MCU datasheet says it already has ESD protection — do I still need external diodes?
On-chip ESD is tested to JEDEC HBM (~2 kV human-body model) which is for handling during manufacturing, not system-level. For IEC 61000-4-2 system testing (±8 to ±15 kV), you need external ESD diodes on any exposed pin.
What's the difference between an ESD diode and a TVS?
Same family — ESD diodes are TVS optimised for very low capacitance and fast response, typically rated up to ~10 A IPP. Power-line TVS (like our Load Dump TVS in DO-218) are rated for hundreds of amps but have much higher capacitance, suitable for DC rails not signal lines.
Should I use uni-directional or bi-directional?
Uni-directional for DC power-fed signals (e.g., a sensor line at 3.3 V). Bi-directional for AC signals or differential pairs that swing both positive and negative (audio, RS-485, antenna lines).
How close to the connector should I place the ESD diode?
As close as possible. The ideal layout is connector pad → ESD diode → trace to IC. Trace inductance before the diode reduces effectiveness; trace inductance after the diode is harmless.
What does 'snapback' mean in an ESD spec sheet?
A snapback diode has trigger voltage > holding voltage. Once it fires, it pulls down to a lower voltage (1-3 V) and clamps very low while shunting current. Best for signal lines where you want lowest possible voltage across the protected IC.
Are Magnias ESD diodes AEC-Q101 qualified?
Most of our high-volume parts are AEC-Q101 qualified for automotive use. P/Ns ending in -A or with the 'A' product-level suffix are explicitly automotive-grade. Industrial / consumer parts use the same die in non-Q-qualified production flow.
Related FAQs
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