RS-485 Port Protection
Evaluation Board 2
5/11 • FU1107
RS-485 Evaluation Board 2 Bill of MaterialsTable 1
No. Part Number Qty. Description Reference
1TBU-CA065-300-WH 2TBU® Single Bidirectional Line 650 V 300 mA TBU® HSP 1, TBU® HSP 2
2MOV-10D201K 2Single Line 10 mm MOV 200 V MOV1, MOV2
3 CDSOT23-SM712 2Dual Bidirectional Line 7 V / 12 V TVS5
Introduction
is 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. e recommended Bourns®
TBU® HSP solution oers 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.
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
conguration of this board uses two MOVs (MOV1,
MOV2) and a single TVS diode array (TVS5). e board
allows dierent congurations:
• 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)
RS-485 Evaluation Board 2 Top Side Layout*
RS-485 Evaluation Board 2 Schematic
Figure 2
Figure 1
TBU® HSP 1
TVS5
TISP1
TISP2
TVS1
TVS2
TVS3
TVS4
GDT3
GDT1MOV1
Line A Unprotected 40 mils trac
eP
rotected Load A
Line B Unprotected 40 mils trac
eP
rotected Load B
J1
J
2
J3
J4
GDT2MOV2
TBU® HSP 2
3
2
1
3
2
1
3
3
2
1
12 21
21
21
21
1
1
22
1
2
1
2
III
I
I
II
II
III
NU
NU
1
2
12
RS-485 Port Protection Evaluation Board 2
Performance Graphs
5/11 • FU1107
ESD +8 KV Contact Discharge (IEC-61000-4-2) Surge 1.2/50 5 KV
120 Vrms 28 Vrms
Figure 3 Figure 4
Figure 5 Figure 6
Ch 1: input voltage / surge / fault to TBU® HSP
Ch 4: TBU® HSP current
1
Ch1 Ch1 116 VMA400 ns
31.60 %
1.00 A ΩCh4
200 V
Ch1 Max
329 V
Ch1 Min
-20.5 V
Trig?PreVu
Ch4 Max
1.98 A
Ch4 Min
-81.1 mA
T
T
4
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
T
Ch 1: input voltage / surge / fault to TBU® HSP
Ch 4: TBU® HSP current
1
Ch1 Line 116 VMA4.00 ms
20.20 %
200 mA ΩCh4
100 V
Ch1 Max
124.4 V
Run Trig’d
Ch4 Max
365.4 mA
Ch4 Min
-322.4 mA
T
T
4
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
T
Ch 1: input voltage / surge / fault to TBU® HSP
Ch 4: TBU® HSP current
4
1
Ch1 Line 116 VMA4.00 ms
20.20 %
200 mA ΩCh4
20.0 V
Ch1 Max
28.3 V
Run Trig’d
Ch4 Max
451.8 mA
Ch4 Min
-395.7 mA
T
T
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
T
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_cpk1114_rs485_circuit_protection_appnote.pdf
“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. • 5/11 • e/FU1107
For further technical support and for complete
circuit protection solutions, please visit
www.bourns.com
Ch 1: input voltage / surge / fault to TBU® HSP
Ch 4: TBU® HSP current
1
Ch1 Ch1 -380 VMA10.0 ns
20.40 %
5.00 A ΩCh4
500 V
Ch1 Max
545 V
Ch1 Min
-390 V
Trig?Run
Ch4 Max
11.3 mA
Ch4 Min
-2.55 A
T
T
4
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
T
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Authorized Distributor
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RS-485EVALBOARD2