Method of measuring characteristic impedance of electrostatic discharge protecting circuit and apparatus for realizing the same

An apparatus for realizing a measurement of a characteristic impedance of an electrostatic discharge protecting circuit comprising:

• a pulse generating circuit;
• a discharge voltage generating circuit for discharging electricity from the electrostatic discharge protecting circuit in response to an input from the pulse generating circuit;
• a voltage measuring circuit and a current measuring circuit which are interposed between the discharge voltage generating circuit, and the electrostatic discharge protecting circuit;
• the voltage measuring circuit measuring a variation with respect to time of a discharge voltage applied to said electrostatic discharge protecting circuit;
• said current measuring circuit measuring a variation with respect to time of a discharge current caused to flow through the electrostatic discharge protecting circuit;
• and
• a controller for instructing the pulse generating circuit, the discharge voltage generating circuit, the voltage measuring circuit, and the current measuring circuit in response to commands from a computer, said controller detecting a state when both the discharge voltage and the discharge current corresponding to each other are attenuated, after both the discharge voltage and the discharge current arrive individually at respective peak values in response to an input to or an output from a computer, the computer determining a ratio of the variation of discharge voltage to the variation of discharge current during the attenuation as an impedance value when the ratio is nearly constant
• wherein inputs based on measured values are inputted from the voltage measuring circuit and the current measuring circuit to said computer.