ESD Testing for RS232 Interface Circuits

ESD Transients During Powered Operation The test methods discussed so far involve testing for permanent damage to the integrated circuit from ESD transients. In today’s portable electronics, interconnection of cables to the communications ports may occur while the equipment is operating. This makes it imperative that the circuit can tolerate the ESD transient with minimal disruption of system operation. LTC’s RS232 interface circuits can withstand 10kV ESD transients while operating, shut down, or powered down. Disruption of data transfer is unavoidable during the ESD transient event, but data transmission may resume upon the completion of the event. Figure 2 is a scope photograph of the data transmission interruption and recovery seen when a –10kV ESD transient strikes a communications line. The test circuit of Figure 3 was used to record this event. The ESD strike is applied to the driver output of an LT1180A and the receiver input of an LT1331. The ESD transient is of too short a duration to be recorded on the photograph, but the effects of the transient can be seen by the corruption of data after the strike. The circuits require about 20μs to recover from the event, after which data transmission continues normally