SP304 Datasheet, PDF (6/12 Pages) Sipex Corporation – RS-232/RS-422 Line Drivers/Receivers

supplying ±2V minimum into a 100Ω load.
Short circuit protection for the RS-422 operat-
ing mode is the same as in the RS-232 mode. The
driver outputs can be shorted to ground for an
infinite duration, with a maximum current of
±100mA.
The RS-422 receivers accept differential signals
at a 1Mbps rate, and translate them to a non-
inverted TTL output. The receivers are speci-
fied with a ±15V differential input voltage,
which means that to operate normally, the dif-
ference betweeen the voltages at the inputs
cannot exceed ±15V. The common mode volt-
age is specified as ±7V. This identifies the
midpoint of the range about which the differen-
tial input must lie so that the receiver can detect
a change of state. Within this ±7V range, the
receivers will recognize a change in state with a
±200mV differential threshold voltage. Since
the RS-232 and RS-422 inputs are shared, all
receiver inputs are protected to ±30V to guard
against inadvertently applying an RS-232 signal
to an input that is configured for RS-422.
Figure 2 shows a typical circuit for the SP304.
In this case the SP304 is shown configured for
one (1) duplex RS-422 and two (2) duplex
RS-232 communication paths.
CONFIGURING THE SP304
Figures 3, 4 and 5 show the various combina-
tions of simultaneous RS-232 and RS-422
operation that can be achieved with the SP304.
Each of these configurations are software
selectable by logic level on the SELECT A and
SELECT B control lines. Configuration can be
changed “on-the-fly”.
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Corporation
SIGNAL PROCESSING EXCELLENCE