As a typical serial differential communication method, RS-485 networking communication interface is widely used in instrumentation, industrial control, mechatronics products, multimedia networks and other fields. However, in actual operation, RS-485 communication transmission lines are often exposed to outdoor environments and are susceptible to lightning surge overvoltage or electrostatic electromagnetic interference.

Since the operating voltage of RS-485 transceiver is low (only 5V) and the withstand voltage range is limited (between -7V and +12V), lightning overvoltage may instantly damage the transceiver and cause communication system failure; electrostatic electromagnetic interference will also have a significant impact on the data transmission of the communication bus.

RS485 protection circuit diagram

Semicon Champoin's CSH712E2B electrostatic ESD protection device is packaged in SOT-23, has a power of 350W, has the characteristics of 7V and 12V asymmetric voltage, the maximum flow rate Ipp can reach 17A, and the capacitance is about 55PF. CSH712E2B has excellent electrostatic protection function, whether it is air discharge or contact discharge, it can achieve ±30KV electrostatic protection.

The rated parameters of CSH712E2B are as follows:

Peak pulse power (tp=8/20μs)@25℃：350W

ESD (IEC61000-4-2 air discharge)@25℃：±30KV

ESD (IEC61000-4-2 contact discharge)@25℃：±30KV

Peak pulse current (tp=8/20μs)@25℃：17A(max.)

Clamping Voltage：26V@17A