SP483EEN-L Datasheet, PDF (7/12 Pages) Exar Corporation – Enhanced Low EMI Half-Duplex RS-485 Transceiver

The SP483E is a half-duplex differential
transceiver that meets the requirements
of RS-485 and RS-422. Fabricated with
an Exar proprietary BiCMOS process, this
product requires a fraction of the power of
older bipolar designs.
The RS-485 standard is ideal for multi-drop
applications and for long-distance interfaces.
RS-485 allows up to 32 drivers and 32 receiv-
ers 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-485 transceivers are equipped with
a wide (-7V to +12V) common mode range
to accommodate ground potential differ-
ences. Because RS-485 is a differential
interface, data is virtually immune to noise
in the transmission line.
Drivers
The driver outputs of the SP483E are dif-
ferential outputs meeting the RS-485 and
RS-422 standards. The typical voltage
output swing with no load will be 0 Volts to
+5 Volts. With worst case loading of 54Ω
across the differential outputs, the drivers
can maintain greater than 1.5V voltage
levels. The drivers have an enable control
line which is active HIGH. A logic HIGH on
DE (pin 3) will enable the differential driver
outputs. A logic LOW on the DE (pin 3) will
tri-state the driver outputs.
The SP483E has internally slew rate lim-
ited driver outputs to minimize EMI. The
maximum data rate for the SP483E drivers
is 250kbps under load.
Receivers
DESCRIPTION
The SP483E receivers have differential
inputs with an input sensitivity as low as
±200mV. Input impedance of the receivers is
typically 15kΩ (12kΩ minimum). A wide com-
mon mode range of -7V to +12V allows for
large ground potential differences between
systems. The receivers have a tri-state en-
able control pin. A logic LOW on RE (pin 2)
will enable the receiver, a logic HIGH on RE
(pin 2) will disable the receiver.
The SP483E receiver is rated for data
rates up to 250kbps. The receivers are
equipped with the fail-safe feature. Fail-
safe guarantees that the receiver output
will be in a HIGH state when the input is
left unconnected.
Shutdown Mode
The SP483E is equipped with a Shutdown
mode. To enable the shutdown state, both
driver and receiver must be disabled simul-
taneously. A logic LOW on DE (pin 3) and a
Logic HIGH on RE (pin 2) will put the SP483E
into Shutdown mode. In Shutdown, supply
current will drop to typically 1µA.
ESD Tolerance
The SP483E incorporates ruggedized ESD
cells on all driver output and receiver input
pins. The ESD structure is improved over our
previous family for more rugged applications
and environments sensitive to electro-static
discharges and associated transients. The
improved ESD tolerance is at least ±15kV
without damage or latch-up.
There are different methods of ESD testing
applied:
a) MIL-STD-883, Method 3015.7
b) IEC61000-4-2 Air-Discharge
c) IEC61000-4-2 Direct Contact
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

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