SP483E_05 Datasheet, PDF (6/11 Pages) Sipex Corporation – Enhanced Low EMI Half-Duplex RS-485 Transceiver

DESCRIPTION...
The SP483E is a half-duplex differential
transceiver that meets the requirements of
RS-485 and RS-422. Fabricated with a Sipex
proprietary BiCMOS process, the SP483E
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 receivers
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 differences. 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 differential
outputs meeting the RS-485 and RS-422 stan-
dards. 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 volt-
age 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 DE (pin 3) will tri-state the
driver outputs.
The SP483E has internally slew rate limited
driver outputs to minimize EMI. The maximum
data rate for the SP483E drivers is 250 Kbps
under load.
Receivers...
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 common mode
range of -7V to +12V allows for large ground
potential differences between systems. The
receivers have a tri-state enable 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 250 Kbps. 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 the driver
and receiver must be disabled simultaneously. 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 device 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 nor latch-up.
There are different methods of ESD testing
applied:
a) MIL-STD-883, Method 3015.7
b) IEC1000-4-2 Air-Discharge
c) IEC1000-4-2 Direct Contact
SP483EDS/05
SP483E Low EMI Half-Duplex RS485 Transceiver
6
© Copyright 2000 Sipex Corporation