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
© Copyright 2002 Sipex Corporation
5
SIPEX [ SIPEX CORPORATION ]
