RS-485 Port Protection Evaluation Board 2 Introduction 1 GDT1 GDT2 1 Line B Unprotected J3 TISP1 I II II I II I 1 2 TVS2 TBU® HSP 2 2 J2 TVS5 2 1 II 3 2 2 MOV2 TVS3 2 GDT3 3 1 TVS1 Load A NU 3 2 2 MOV1 I 1 2 J1 Protected 2 TBU® HSP 1 1 1 40 mils trace 1 Unprotected 2 TVS4 1 NU 3 1 Line A 1 2 1 This evaluation board serves as an aid in evaluating circuit protection on RS-485 serial device port solutions using Bourns® TBU® High-Speed Protector (HSP), MOV and TVS products to meet the required industry standards on RS-485 port interfaces. The recommended Bourns® TBU® HSP solution offers enhanced performance features over competing technologies, which can help the design engineer to increase the surge & transient protection level on RS-485 ports and place the entire circuit protection solution into a smaller PCB area. Bourns has developed a RS-485 evaluation board (measuring 50 mm x 25 mm x 1.2 mm) manufactured using FR4 PCB with nickel gold plating on top and bottom sides. TISP2 1 2 2 40 mils trace Protected Figure 1 RS-485 Evaluation Board 2 Schematic Figure 2 RS-485 Evaluation Board 2 Top Side Layout* Table 1 RS-485 Evaluation Board 2 Bill of Materials Load B J4 How to Connect the Evaluation Board for Test Set-up • Connect J1 and J2 to the exposed lines. • Connect J3 and J4 to the RS-485 IC device. * In addition to the two TBU® HSPs, the default configuration of this board uses two MOVs (MOV1, MOV2) and a single TVS diode array (TVS5). The board allows different configurations: • 2 MOVs (MOV1 and MOV2) may be replaced by a) 2 single 2031 GDTs (GDT1 and GDT2) or b) a dual 2030 GDT (GDT3, not yet released) • 1 TVS diode array (TVS3) may be replaced with a) 2 SMB TVS diodes (TVS1, TVS2) or b) 2 SOT23 TVS diodes (TVS3, TVS4) or c) 2 SOT23-5 thyristor devices (TISP1, TISP2) No. Part Number Qty. Description Reference 1 TBU-CA065-300-WH 2 TBU® Single Bidirectional Line 650 V 300 mA TBU® HSP 1, TBU® HSP 2 2 MOV-10D201K 2 Single Line 10 mm MOV 200 V MOV1, MOV2 3 CDSOT23-SM712 2 Dual Bidirectional Line 7 V / 12 V TVS5 11/11 • FU1107 RS-485 Port Protection Evaluation Board 2 Performance Graphs Run Trig? T PreVu Trig? T T T Ch1 Max 329 V Ch1 Max 545 V Ch1 Min -20.5 V 1 4 Ch1 Min -390 V 1 4 Ch4 Max 11.3 mA Ch4 Max 1.98 A Ch4 Min -81.1 mA Ch4 Min -2.55 A Ch1 500 V M 10.0 ns Ch4 5.00 A Ω Ch 1: input voltage / surge / fault to TBU® HSP Ch 4: TBU® HSP current Figure 3 A Ch1 Ch1 -380 V M 400 ns Ch4 Figure 4 Trig’d T 1.00 A Ω A Ch1 The ohm unit following the current units shown for Channel 4 (i.e. AOhm) indicates that a 50 ohm termination was used internal to the oscilloscope Surge 1.2/50 5 KV Run Trig’d T T 116 V T 31.60 % Ch 1: input voltage / surge / fault to TBU® HSP Ch 4: TBU® HSP current The ohm unit following the current units shown for Channel 4 (i.e. AOhm) indicates that a 50 ohm termination was used internal to the oscilloscope ESD +8 KV Contact Discharge (IEC-61000-4-2) Run 200 V T 20.40 % T Ch1 Max 124.4 V 1 4 Ch1 Max 28.3 V Ch4 Max 365.4 mA 1 4 Ch4 Max 451.8 mA Ch4 Min -322.4 mA Ch1 100 V M 4.00 ms Ch4 200 mA Ω 116 V Ch1 20.0 V M 4.00 ms Ch4 T 20.20 % Ch 1: input voltage / surge / fault to TBU® HSP Ch 4: TBU® HSP current Figure 5 A Line Ch4 Min -395.7 mA Figure 6 A Line 116 V T 20.20 % Ch 1: input voltage / surge / fault to TBU® HSP Ch 4: TBU® HSP current The ohm unit following the current units shown for Channel 4 (i.e. AOhm) indicates that a 50 ohm termination was used internal to the oscilloscope 120 Vrms 200 mA Ω The ohm unit following the current units shown for Channel 4 (i.e. AOhm) indicates that a 50 ohm termination was used internal to the oscilloscope 28 Vrms Reference For more information on implementing advanced circuit protection technologies for RS-485 ports, please review the Bourns RS-485 application note: http://www.bourns.com/data/global/pdfs/Bourns_RS-485_AppNote.pdf For further technical support and for complete circuit protection solutions, please visit www.bourns.com 11/11 • FU1107 “TBU” is a registered trademark of Bourns, Inc. in the U.S., Taiwan and European Community. “Bourns” is a registered trademark of Bourns, Inc. in the U.S. and other countries. COPYRIGHT© 2011 • BOURNS, INC. • 11/11 • e/FU1107