AXIOMTEK AX10445 Series, Руководство пользователя

Страница: 28 / 58

AX10445 Module Series User
’
s Manual
Technical Reference
20
3.4 Isolation Circuit (for AX10445A)
The AX10445A (isolated version) is equipped with eight 6N136
for isolation purpose. 6N136 is a high-speed opto-coupler
having a very high common-mode transient immunity.
At operating environments having a very large common mode
noise, we highly recommend using the AX10445 with isolation
to avoid common mode noise interface.
The driver and receiver circuits of AX10445A are isolated from
PC electrical environment. You must practice extra care
when connecting wires to and from the 9-pin D-type
connectors.
Do not interconnect the signal ground and
shielding (connector case) ground together for AX10445A.
3.5 Termination Resistor
As the AX10445 use differential signal lines in communication,
a terminating resistor for impedance matching should be
connected bet ween the parallel transmission line. While the
value of these terminating resistors are corresponding to the
characteristic impedance of the wires (cables).
The ohmic value of termination resistor is about 100
Ω
through
300
Ω
. User has to install them if need .
Onboard the AX10445, the positions of termination resistors
are marked as:
RT1
→
RT8
RT1 → CTS1
RT2 → RX1
RT3
→
RTS1
RT4 → TX1
RT5 → RTS2
RT6
→
RX2
RT7 → TX2
RT8 → CTS2
3.6 Surge Absorber
To protect the module from electrical power surges, there are
8 varistors connected between each of the communication
wire lines and ground.
R V 1-RV8 indicate the locations of the surge absorbers.