30. TVS Diode for RS-485 Communication Bus Protection

Rohit is designing an industrial controller that communicates with field devices over an RS-485 bus. 

The RS-485 lines (A and B) run through long cables across the factory floor, making them vulnerable to ESD, surge transients, and ground potential differences. 

To protect the RS-485 transceiver IC from transient damage, he needs to place a bidirectional TVS diode on each bus line. 

Key requirements: 

• RS-485 bus voltage range is −7V to +12V under normal operation 

• TVS standoff voltage: 12V to 15V (above normal bus voltage) 

• Clamping voltage: ≤30V (transceiver can handle brief transients up to ±30V on bus pins) 

• Capacitance: ≤50pF (to avoid degrading signal at standard baud rates) 

• SMD package: SOD-882 

The company's approved vendor list (AVL) specifies Littelfuse for circuit protection components, so the part must be selected from Littelfuse on DigiKey. 

Help him select a suitable bidirectional TVS diode from Littelfuse on DigiKey. 

Make sure it has the correct standoff voltage, low clamping voltage, low capacitance, and works reliably in industrial temperatures.