1、 RS-485 standard

       Industrial and instrumentation (I&I) applications often require data transmission between multiple systems over long distances, including industrial automation, process control, motor control and motion control, remote terminals, building automation (HVAC, etc.), security systems, and renewable energy.
       The RS-485 electrical standard is one of the most widely used physical layer specifications in I&I applications. In practical applications, lightning strikes, power induction, direct contact, power fluctuations, inductive switching, and electrostatic discharge may generate large transient voltages, causing damage to RS-485 transceivers.


2、 Application background

       1. RS485 wiring is very long and prone to overvoltage
       2. RS485 wiring placed outdoors is susceptible to lightning strikes
       3. RS485 wiring is susceptible to interference from other lines
       To protect circuits, equipment, or components from transient overvoltage surges higher than normal operating voltage, TSS semiconductor discharge tubes can be selected for their protection.

3、 RS-485 protection scheme


       RS-485 protection scheme


4、 Advantages of the plan

       1. This scheme adopts TSS semiconductor discharge tubes with very low residual voltage, effectively protecting RS485 chips and meeting surge standards such as IEC61000-4-5 and GBT17626.5
       2. The TSS semiconductor discharge tube in the scheme has a reaction time of ns level, which can prevent surges and static electricity, meeting static electricity standards such as IEC61000-4-2 and GBT17626.2
       3. The TSS semiconductor discharge tube in the scheme has a small junction capacitance, no signal attenuation, and does not affect the transmission of control lines
       4. It can pass 10/700 μ s (equivalent internal resistance of 40ohm) surge test and electrostatic test. Please refer to the circuit protection diagram and specific parameters of TSS semiconductor discharge tube for specific protection level.

5、 Solution application

       1. Surveillance/Security System
       2. Access control system
       3. Railway signal control lights
       4. Intelligent Transportation System
       5. Electricity meter/water meter/instrumentation
       6. Optical transceiver