ESD保护I/O端口

• What level of ESD voltage is the IC guaranteed to withstand, and by what test method was that level established? Different test methods yield different voltage ratings. Currently, the recommended approach includes both IEC 1000-4-2 and the modified 3015.7 method.
  
• Will ESD cause latchup in the IC?Latchup is a critical problem. The IC might stop functioning if ESD causes latchup in the circuit. The resulting supply current (as much as 1A) may destroy the IC.
  
• Does the IC's ESD protection affect normal operation? Normal operation can cause latchup in the internal protection structure if it is poorly designed.
  
• Must you observe special precautions when applying the IC? Bipolar ICs might require expensive, low-ESR capacitors or a ground plane with low ac impedance. It's best to learn of these requirements at the outset.
  
• What is the IC's maximum specified slew rate? An IC susceptible to latchup because of its ESD-protection structure might specify an unusually low maximum slew rate to avoid triggering the latchup condition.
  
• How does the IC respond to an ESD test that covers the entire range for which voltage protection is guaranteed? Trigger mechanisms for an ESD-protection structure can kick in at different voltage ranges, leaving open "windows" with no protection. (Such a device might survive ±10kV but fail at ±5kV, for instance.) Maxim recommends that an ESD test cover the entire range in 200V increments.

References

1. Electrostatic Discharge, Protection Test Handbook, 2nd Edition,
   KeyTek Instrument Corporation, 1986, p. 7.