Internet ESD-shunt diode protected by delayed external MOSFET switch
Electro-static-discharge (ESD) protection of an integrated circuit chip is enhanced by an EOS protection circuit using external components. An external MOSFET is placed in series with the ground pin of the integrated circuit chip. The external MOSFET has a gate coupled to a power bus through a gate resistor, and is bypassed by an ESD capacitor. The external MOSFET turns on after a delay when power is applied during hot insertion. The delay is determined by a power-to-ground bypass capacitor. The time delay of the on stage of the MOSFET inhibits ground current generated by EOS voltage leaked from the power supply through parasitic resistances, capacitances, and inductances, preventing ESD-protection diodes inside the chip from burning out from this EOS pulses that occur during hot insertion. The ESD bypass capacitor shunts the initial ESD pulse to ground before the external MOSFET turns on.
Pericom Semiconductor Corp.
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