SP306 Datasheet, PDF (4/6 Pages) Sipex Corporation – RS-422/RS-423 Line Drivers/Receivers

and sink current capability. The RS423 line
drivers convert TTL logic levels into inverted
RS-423 output signals. All line drivers are inter-
nally protected against short circuits on their
outputs.
The RS-422 receivers convert the RS-422 dif-
ferential input signals into non–inverted TTL
logic levels. Receiver input thresholds are
±200mV. The RS-422 receivers can receive
input data up to 1Mbps. The RS-423 receivers
convert the RS-423 input signals into inverted
TTL output logic levels. The RS-423 receivers
have an input threshold of ±200mV, and can
receive data up to 100kbps.
A loopback test mode is provided that puts the
driver outputs into a high impedance tri–state
level, and routes the driver outputs to their
associated receiver inputs. In this configuration,
the signal path is non–inverting from the TTL
driver inputs to the receiver TTL outputs. This
operating mode allows the controlling system to
perform diagnostic self–test of the RS-422/
RS-423 transceiver circuitry at speeds up to
3kbps.
APPLICATION INFORMATION
Control Logic Configuration
Software control of the SP306 is via two select
pins (7 and 8) and a loopback control pin (22).
SELECT A and SELECT B allow the user to
program the SP306 for four different interface
modes. Loopback mode can be selected in any
of these interface modes. The figures that follow
outline the various operating modes that are
supported by the SP306.
SUPPLY
+5V +12V –12V
SUPPLY
+5V +12V –12V
SELECT A = 0
SELECT B = 0
LOOPBACK = 1
28 1 15
V_CC V_DD V_EE
7
SELECT A
8 _{SELECT B}
22 _LOOPBACK
SELECT A = 0
SELECT B = 0
LOOPBACK = 0
28 1 15
V_CC V_DD V_EE
7
SELECT A
8 _{SELECT B}
22 _LOOPBACK
T_OUTA1
R_INA1
T_INA
T_OUTA*1
R_OUTA R_INA1
T_INA
R_OUTA
T_OUTB1
R_INB1
T_INB
T_OUTB*1
R_OUTB R_INB1
T_INB
R_OUTB
14 _GND
SP306
14 _GND
SP306
RS-423 DRIVER
* Tri–state output
RS-423 RECEIVER
RS-422 RECEIVER
RS-422 DRIVER
* Tri–state output
Figure 1. Control Input Configuration — SELECT A = 0, SELECT B = 0
92
Corporation
SIGNAL PROCESSING EXCELLENCE