SP3483EN-L Datasheet, PDF (7/9 Pages) Exar Corporation – +3.3V Low Power Slew Rate Limited Half-Duplex RS-485 Transceiver

The SP3483 device is part of a family of
+3.3V low power half-duplex transceivers
that meet the specifications of the RS-485
and RS-422 serial protocols. This device is
pin-to-pin compatible with the Exar SP483
device as well as popular industry standards.
The SP3483 features Exar's BiCMOS pro-
cess allowing low power operation without
sacrificing performance.
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 SP3483 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
+3.3 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
force the driver outputs into high impedance
(high-Z).
The SP3483 has internally slew rate lim-
ited driver outputs to minimize EMI. The
transceivers will operate up to 250kbps.
The 250mA I_SC maximum limit on the driver
output allows the SP3483 to withstand an
infinite short circuit over the -7.0V to +12V
common mode range without catastrophic
damage to the IC.
Receivers
DESCRIPTION
The SP3483 receiver has differential inputs
with an input sensitivity as low as ±200mV.
Input impedance of the receivers is typically
15kΩ (12kΩ minimum). A wide common
mode range of -7V to +12V allows for large
ground potential differences between sys-
tems. The receiver of the SP3483 has a tri-
state enable control input RE (Pin 2). A logic
LOW on RE will enable the receiver, a logic
HIGH on RE will disable the receiver.
The receiver of the SP3483 will operate
up to 250kbps. The receiver is equipped
with the fail-safe feature. Fail-safe guar-
antees that the receiver output will be in a
HIGH state when the input is left uncon-
nected (open circuit).
Shutdown Mode
The SP3483 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
SP3483 into Shutdown mode. In Shutdown,
supply current will drop to typically 1µA,
10µA maximum.
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

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