A Circuit for Testing Common-mode Transient Immunity (dv/dt) of Isolated Current Sense Amplifiers and Drivers

The common-mode transient immunity (dv/dt) ratings of isolated drivers and current sense amplifiers are important parameters for their operational ruggedness. A circuit for testing dv/dt immunity consisting of a synchronous buck converter is presented in this work. The high and low side grounds of the device under test (DUT) are connected between the switching node and the buck converter ground. By changing the buck converter drivers' voltages, the slew up and down of the switching node is also changing. The results for the current sense amplifiers show a maximum slew rate of the rising edge of 108 V/ns, and a recovery time of less than 60 ns, while at the maximum slew rate of the falling edge, of 69 V/ns, the recovery time is less than 100 ns. Using the proposed circuit eliminated any risk of damaging the MOSFETs and drivers during the immunity testing. The setup provides repeatable results.