3.2.3 Conclusion of Test Results

The test results show that by adding the TVS diode, the transient blocking unit, the metal oxide varistor, and the pulse proof resistors to the A and B bus lines of both the SN65HVD3082E and SN65HVD82 transceivers, the transient immunity increases significantly. The designs pass IEC ESD level 4 criteria, IEC EFT level 4 criteria, and IEC surge level 4 criteria. Both designs also fall into the “special” characteristic per the IEC ESD standard as the SN65HVD3082E passes IEC ESD up to ±14 kV while the SN65HVD82 passes up to ±30 kV IEC ESD, surpassing the level 4 ESD voltage.

Not every design or application will require ±30 kV of ESD protection, but for those applications that do, the SN65HVD82 coupled with the CDSOT23-SM712 TVS diode, the TBU-CA0065-200-WH, and the MOV-14D561KTR from Bourns will provide this as well as level 4 IEC ESD and surge protection.

For designs that do not require this level of protection but need to be rated up to level 4 IEC ESD (±8 kV), coupling the SN65HVD3082E with the same CDSOT23-SM712 TVS diode, TBU-CA0065-200-WH, and MOV-14D561KTR from Bourns takes a standard RS-485 transceiver with no integrated IEC ESD protection to ±14 kV IEC ESD protection and level 4 IEC EFT/surge.

Certain specialized transceivers are available that can provide some level of IEC 61000-4-5 surge immunity without the need for any external protection components. For example, the THVD1429 device is designed to withstand 1.2/50-µs surges up to 2.5 kV. This device would be suitable for applications requiring up to Level 3 protection.