SP322_05 Datasheet, PDF (11/13 Pages) Sipex Corporation – Programmable V.11/V.35 Transceiver

Termination Circuitry
Unique to Sipex, the SP322 provides internal
resistor networks for V.35 as well as the cable
termination for V.11. The resistor network for
the V.35 receivers are configured as a typical
V.35 receiver using two 51Ω resistors in series
tied to the A and B inputs with a 124Ω center-tap
resistor to ground. The network is internally
switched on during V.35 mode (V.11/V.35 =
V_CC) using high performance, low r_ON transis-
tors. The transistors can operate efficiently over
+7V to -7V, and can tolerate over +10V to -10V
without damage. This termination provides the
proper V.35 receiver input impedance of 100Ω
and short-circuit impedance at 2V of 150Ω with
10% accuracy.
The configuration for the V.11 receiver input
resistor network is similar to the V.35 network
except that the 124Ω resistor is disconnected
(V.11/V.35 = 0V). A series resistor is also
added increase the input impedance to over
120Ω for the V.11 cable termination. The
minimum resistance per the ITU V.11 specifica-
tion is 100Ω. The V.11 termination can be
switched off using the V.11_TERM pin. For a
terminated V.11 receiver, this pin is at a logic
"1". A logic "0" will inform the switches to
disconnect the V.11 termination.
Shutdown
The SP322 includes a shutdown pin (SD) which
disables the charge pump and all power con-
suming circuitry to provide low I_CC. A logic "1"
to the SD pin will shut down the SP322 where it
will draw less than 20µA of current.
NET1/2 European Compliancy
As with all of Sipex's previous multi-protocol
transceiver ICs, the SP322 drivers and receivers
have been designed to meet all electrical
specifications for ITU V.11 and V.35.
Furthermore, it is internally tested and will pass
the NET1/2 physical layer testing requirements.
Please note that although the SP322 adheres to
NET1/2 testing, any complex or unusual
configuration should be double-checked to
ensure NET compliance. Consult factory for
details.
Applications Information
The SP322 is designed for serial port applica-
tions needing V.11 and V.35 transceivers. The
SP322 supports a variety of physical layer
protocols such as EIA-530, EIA-530A, RS-449,
and V.36 where V.11 transceivers are used for
clock and data signals. The termination resistors
are recommended for crosstalk and reflections
elimination under higher speed operation.
Internal termination solves many headaches and
configuration hassles with implementing V.11
and V.35. The SP322 provides a simple, low-
cost solution for the clock and data lines for
synchronous serial ports. The handshaking lines
such as CTS, DTR, etc. can be implemented
using discrete RS-422 or RS-232 transceivers,
depending on the mode supported. Sipex
supplies either differential (V.11) or single-
ended (V.28) discrete transceiver products
to mate with the SP322.
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