3-2(1) Low dynamic resistance (RDYN)
In the event of an ESD strike, the ESD current flows to both the ESD protection diode and the device under protection (DUP). It is important to reduce the current flowing to the DUP (i.e., increase the current shunted through the ESD protection diodes).
Nowadays, the datasheets for ESD protection diodes show their dynamic resistance (RDYN). RDYN is the slope of the VF–IF curve in reverse conduction mode. In the event of an ESD strike, ESD protection diodes with lower dynamic resistance conduct more current at a given voltage.
From the connector side, the impedances of the ESD protection diode and the DUP can be regarded as being connected in parallel. If the ESD protection diode has low impedance (i.e., dynamic resistance), most of the surge current is shunted through the ESD protection diode, reducing the current that flows to the DUP and therefore the possibility of its destruction.