Datasheet

3.3V
PSU1
R
JMP3
1
2
VCC
3
4
JMP2
1
2
VCC
3
4
/RE
DE
JMP6
1
2
3
4
B
A
1
JMP11
2
3
1 2 3
TB1
GND
EARTH
VCC
1
2
3
TB2
Scope
Ch4 Ch3 Ch2 Ch1
B
A
PSU2
Signal
Generator
JMP4
1
2
VCC
3
4
D
JMP3
1
2
VCC
3
4
JMP2
1
2
VCC
3
4
/RE
DE
1
JMP14
2
3
1 2 3
TB1
GND EARTH VCC
1
2
3
TB2
B
A
3.3V
3.3V
PSU1
V
CM
PSU2
Scope
Ch4 Ch3 Ch2 Ch1
3.3V
Signal
Generator
JMP4
1
2
VCC
3
4
R
D
JMP3
1
2
VCC
3
4
JMP2
1
2
VCC
3
4
/RE
DE
JMP6
1
2
3
4
1
JMP11
2
3
1
JMP14
2
3
1 2 3
TB1
GND
EARTH
VCC
JMP7
1
2
3
4
R9
375W
R8
375W
3.3V
www.ti.com Powering Up the EVM and Taking Measurements
• replace R5 (120-Ω default) with 60 Ω
• replace R8 and R9 (0-Ω default) with 375 Ω
• connect pin 2 of JMP7 with pin 1 and pin 3 with pin 4
• replace the previous wire-bridge at TB1 with a second power supply unit (PSU2) and connect the
ground terminals of both, PSU1 and PSU2 with a wire-bridge, as shown in Figure 8.
Figure 8. RS-485 Half-Duplex EVM Setup for Maximum Loading
Note that Figure 8 only shows the wiring of PSU2 for positive common-mode voltages. For negative
V
CM
, connect the ground terminal of PSU2 with pin 1 of TB1 (EARTH), and the V
CM
-output of PSU2
with the ground terminal of PSU1.
Figure 9. RS-485 Half-Duplex EVM Configurations: Left as Receiver EVM, Right as Transmitter EVM
7
SLLU173B–October 2012–Revised June 2013 RS-485 Half-Duplex Evaluation Module
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