SP481_04 Datasheet, PDF (5/10 Pages) Sipex Corporation – Low Power Half-Duplex RS-485 Transceivers

DESCRIPTION
SP481, SP483, SP485
The SP481, SP483, and SP485 are half-duplex
differential transceivers that meet the require-
ments of RS-485 and RS-422. Fabricated with a
Sipex proprietary BiCMOS process, all three
products require 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
SP481, SP483, SP485
The driver outputs of the SP481, SP483, and
SP485 are differential 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 of
the SP481, SP483 and SP485 have an enable
control line which is active HIGH. A logic
HIGH on DE (pin 5) will enable the differential
driver outputs. A logic LOW on DE (pin 5) will
tri-state the driver outputs.
The transmitters of the SP481 and SP485 will
operate up to at least 5Mbps. The SP483 has
internally slew rate limited driver outputs to
minimize EMI. The maximum data rate for the
SP483 driver is 250kbps.
Receivers
SP481, SP483, SP485
The SP481, SP483, and SP485 receivers have
differential inputs with an input sensitivity as
low as ±200mV. Input impedance of the receiv-
ers is typically 15kΩ (12kΩ minimum). A wide
common mode range of -7V to +12V allows for
large ground potential differences between
systems. The receivers of the SP481, SP483
and SP485 have a tri-state enable control pin.
A logic LOW on RE (pin 4) will enable the
receiver, a logic HIGH on RE (pin 4) will disable
the receiver.
The receiver for the SP481 and SP485 will
operate up to at least 5Mbps. The SP483 receiver
is rated for data rates up to 250kbps. The receiver
for each of the three devices is 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 and floating.
Shutdown Mode
SP481/SP483
The SP481 and SP483 are 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 5) and
a logic HIGH on RE (pin 4) will put the SP481
or SP483 into Shutdown mode. In Shutdown,
supply current will drop to typically 1µA.
Rev. 07/28/04
SP481/483/485 Low Power Half-Duplex RS485 Transceivers
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© Copyright 2002 Sipex Corporation