RS-485EVALBOARD1 Bourns

RS-485 Port Protection Evaluation Board 1 Introduction This Evaluation Board serves as an aid in TBU HSP 1 evaluating circuit protection on RS-485 1 12 1 OUT1 TVS3 serial device ports, using two Bourns 1 IN1 TVS1 3 GDT1 TVS5 TBU High-Speed Protectors (HSP), two 2 1 1 3 3 1 GDT3 fast-acting GDTs and two TVS diodes to GND 2 2 3 GND meet the required industry standards on GDT2 1 TVS2 RS-485 port interfaces. The recommended TVS4 11 2 1 OUT2 Bourns TBU device solution, with a IN2 TBU HSP 2 low capacitance GDT, oerff s enhanced high-speed performance features over Figure 1 RS-485 Evaluation Board Schematic competing technologies, which can help the design engineer increase the surge and transient protection level on RS-485 ports and place the entire circuit protection solution into a smaller reduced PCB area. Bourns has developed an RS-485 Evaluation Board (measuring 45 mm x 21mm x 1.2 mm) manufactured using FR4 PCB with nickel gold plating on the top and bottom sides. How to Connect the Evaluation Board for Test Set-up Connect IN1 and IN2 to the Figure 2 RS-485 Evaluation Board Top Side Layout* exposed lines. Connect OUT1 and OUT2 to the RS-485 IC device. Table 1 RS-485 Evaluation Board Bill of Materials * The default congfi uration of this board uses 2 GDTs No. Part Number Qty. Description Reference (GDT1, GDT2) and discrete SMB TVS diodes (TVS1,TVS2). The board allows dierff ent congfi urations: 1 TBU-CA065-200-WH 2 TBU Single Bidirectional Line 650 V 200 mA TBU HSP 1, TBU HSP 2 2 single 2031 GDTs (GDT1 and GDT2) may be replaced by a dual 2030 GDT (GDT3, not yet released) 2 2031-23T-SM-RPLF 2 Single Line Fast-acting GDT 650 V GDT1, GDT2 2 SMB TVS diodes (TVS1 and TVS2) may be replaced with a) 2 SOT23 TVS diodes (TVS3, TVS4) 3 SMBJ12CA 2 Single Bidirectional Line TVS 12 V SMB TVS1, TVS2 or b) a single TVS diode array (TVS5) 4/11 FU1106 1 2 21 21 12 21RS-485 Port Protection Evaluation Board 1 Performance Graphs Run T Trigd PreVu T Trig T T 1 Ch1 RMS Ch1 Max 126.7 V 508 V 1 Ch4 Max 2 371.2 mA Ch4 Min Ch4 Max -359.9 mA 1.74 A 4 4 Ch1 200 V Ch2 20.0 V MA2.00 ms Line -3.98 V Ch1 200 V MA200 ns Ch1 -172 V Ch4 200 mA Ch4 1.00 A T 27.20 % T 31.00 % Ch 1: Surge generator Ch 1: AC power generator The ohm unit following the current units The ohm unit following the current units Ch 2: Voltage on protected side of world (downstream Ch 2: Consumed current (TBU HSP Trigger current) shown for Channel 4 (i.e. AOhm) shown for Channel 4 (i.e. AOhm) Note: The noise generated by the GDT when it res of TBU device at SMBJ12CA TVS diode side) indicates that a 50 ohm termination was indicates that a 50 ohm termination was causes a ground bounce and is reected in current Ch 4: Current consumed (TBU HSP trigger current) used internal to the oscilloscope used internal to the oscilloscope measurement at the time the GDT device is triggered. Figure 3 Power Cross 120 V Figure 4 Slew Rate 1 KV/s rms Reference PreVu T T For more information on implementing advanced circuit protection technologies for RS-485 ports, please review the Bourns RS-485 application note: 1 Ch1 Max