SP431 Datasheet, PDF (6/15 Pages) Sipex Corporation – High Speed, +3.3V Quad RS-422 Differential Line Driver

DESCRIPTION
The SP431 is a low-power quad differential line
driver designed for digital data transmission
meeting the specifications of the EIA standard
RS-422 serial protocol. The SP431 features
Sipex's BiCMOS process allowing low power
operational characteristics of CMOS technol-
ogy while meeting all of the demands of the
RS-422 serial protocol up to 60Mbps under load
in harsh environments.
The RS-422 standard is ideal for multi-drop
applications and for long-distance communica-
tion. The RS-422 protocol allows up to 10
drivers to be connected to a data bus, making it
an ideal choice for multi-drop applications. Since
the cabling can be as long as 4,000 feet, RS-422
drivers are equipped with a wide common mode
output range to accommodate ground potential
differences. Because the RS-422 is a differential
interface, data is virtually immune to noise in
the transmission line.
The SP431 accepts TTL or CMOS input levels
and translates these to RS-422 output levels. The
SP431 features active HIGH and active LOW
driver enable controls common to all four driver
channels see Figure 8. A logic HIGH on the
ENABLE pin (pin 4) or a logic LOW on the
ENABLE pin (pin 12) will enable the differential
driver outputs. A logic LOW on the ENABLE
pin (pin 4) or a logic HIGH on the ENABLE pin
(pin 12) will tri-state the driver outputs.
The RS-422 line driver outputs feature high
source and sink current capability. All drivers
are internally protected against short circuits on
their outputs. The driver outputs are short-circuit
limited to 150mA. The driver output skew times
are typically 0.5ns.
To minimize reflections, the multipoint bus
transmission line should be terminated at both
ends in its characteristic impedance, and stub
lengths off the main line should be kept as short
as possible.
ENABLE
DATA
ENABLE
*RT
DATA
OUTPUT
*RT is optional although highly
recommended to reduce reflection.
Figure 7. Two-Wire Balanced System, RS-422
ENABLE
LOW
ENABLE
HIGH
Input
don't care
Non-
Inverting
Output
tri-state
Inverting
Output
tri-state
HIGH
don't care
LOW
LOW
HIGH
don't care
LOW
HIGH
HIGH
LOW
Figure 8. Truth Table, Enable / Disable Function
Common to All Four RS-422 Drivers
SP431DS/08
SP431 High Speed, +3.3V Quad RS-422 Differential Line Driver
6
© Copyright 1997 Sipex Corporation