ELECTROSTATIC DISCHARGE PROTECTION CIRCUITS USING POLARIZED AND CONNECTED PNP TRANSISTOR CHAINS

摘要

In device requiring ESD protection, a bias network (26) is used to augment the diode string to distribute small but significant forward current to the diodes. Also employed is the use of cantilever diodes (30) which provide PNP Darlington gain block for ESD protection rather than for amplifying signals in bipolar ICs. In one embodiment, the termination is the principal element of the device novelty and that which makes the device "stand alone". The termination supplies final base current to the gain block for a limited amount of time, so that ESD charge can be shunted harmlessly through the PNP chain, but assures that the structure draws no current from a stable power supply long term. The entire structure is able to absorb noise spikes as well as ESD pulses. The termination also makes provisions for discharging its capacitor between ESD pulses, as is necessary for standardized testing. The invention has value as an IC power supply clamp, and reduce the damage often seen on IC power supplies during extensive ESD testing. IMAGE