SP503(2000) 데이터 시트보기 (PDF) - Signal Processing Technologies
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SP503 Datasheet PDF : 13 Pages
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SP503 V.35 External Termination
Resistors
V.35 implementation requires external resistors
to be connected to the driver outputs and re-
ceiver inputs. The resistors are needed for
reducing signal levels and maintaining input
and output impedance levels that conform to
CCITT Recommendation V.35. The drawings
below offer both receiver input termination and
driver output termination configurations that
will comply to V.35.
As you may know, the termination resistors are
for V.35 mode only and have to be disconnected
when another mode is programmed. There are
a few ways to connect and disconnect the net-
work. One method is to add a daughter-card
option slot onto the main printed circuit board
where the SP503 is mounted. This allows the
user to add a mini-PC card that contains the V.35
network to be connected to the driver outputs
and receiver inputs. Another method is to
implant the V.35 network into a cable if the user
requires conversion cables to switch from one
protocol to another. For example, if the serial
port has a DB-25 connector and requires an
ISO-2593 connector for V.35; a DB-25 to
ISO-2593 conversion cable containing the V.35
network is connected to the port.
Of course this method will not allow program-
mability to the serial port if the user wants to run
various protocols to that port. To actively switch
protocols by software control, you can use ana-
log switches or relays. Sipex recommends us-
ing low-ON resistance analog switches, such as
Siliconix DG643© analog switches for the driver
outputs, and solid-state relays such as the AT&T
LH1514© for the receiver inputs. See opposite
page for an example of the SP503 V.35 configu-
ration. For other termination networks, please
consult the factory.
A
50Ω
120Ω
50Ω
B
ZSOURCE = 97Ω [90Ω to 110Ω]
ZSC = 148Ω [135Ω to 165Ω]
V.35 Receiver Input Termination Resistor Network
200Ω
A
232Ω
-5V ±5%
232Ω
107Ω
100Ω
LOAD
Typical values
200Ω
B
ZSOURCE = 96Ω [50Ω to 150Ω]
ZSC = 154Ω [135Ω to 165Ω]
VD = 0.55V [+0.44V to +0.66V]
VDC_OFF = 0.0V [-0.6V to +0.6V]
V.35 Driver Output Termination Resistor Network
SP503AN
SP503 Application Note
6
© Copyright 2000 Sipex Corporation
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