RS-485 Port Protection
Evaluation Board 2
Introduction
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.
2
1
Line A
Unprotected
1
40 mils trace
1
2
Protected
1
1
Load A
II
2
1
J1
MOV1
2
GDT1
1
3
TBU® HSP 1
I
3
TVS1
2
TVS3
2
NU
TVS5
3
TISP1
II
J3
I
1
2
GDT3
2
2
2
2
II
3
I
NU
MOV2
1
1
2
GDT2
1
TBU® HSP 2
2
TVS2
1
TVS4
1
II
I
TISP2
1
2
J2
Line B
Unprotected
40 mils trace
Protected
Load B
J4
Figure 1
RS-485 Evaluation Board 2 Schematic
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.
Figure 2
* 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)
RS-485 Evaluation Board 2 Top Side Layout*
Table 1
RS-485 Evaluation Board 2 Bill of Materials
No.
1
2
3
Part Number
TBU-CA065-300-WH
MOV-10D201K
CDSOT23-SM712
Qty.
2
2
2
Description
TBU® Single Bidirectional Line 650 V 300 mA
Single Line 10 mm MOV 200 V
Dual Bidirectional Line 7 V / 12 V
Reference
TBU® HSP 1, TBU® HSP 2
MOV1, MOV2
TVS5
11/11 • FU1107
BOURNS [ BOURNS ELECTRONIC SOLUTIONS ]
