Test Circuit for Machine Model
The configuration is similar to the human body model except for the discharge resistor, which was replaced by an inductor. This is because charged metal parts in machines have very low resistances. A well-known consequence of not having a discharge resistor is uncontrolled current. No control over current transients results in unknown rise times that allow bypass of ESD protection and destruction of the DUT (at voltages near 500 V). This is one reason why the machine model has lost its popularity. The charged-device model arises due to ESD during PCB mounting of the integrated circuit. It took a tedious investigation to prove this phenomenon, where the integrated circuit gains charge as it slides along the plastic rails of the production line and discharges upon touchdown on the PCB.