SP481E_07 Datasheet, PDF (6/11 Pages) Sipex Corporation – Enhanced Low Power Half-Duplex RS-485 Transceivers

DESCRIPTION
The SP481E and SP485E are half-duplex differ-
ential transceivers that meet the requirements 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
The driver outputs of the SP481E and SP485E
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 differ-
ential outputs, the drivers can maintain greater
than 1.5V voltage levels. The drivers of the
SP481E, and SP485E 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 transmitters of the SP481E and SP485E
will operate up to at least 10Mbps.
Receivers
The SP481E and SP485E receivers have differ-
ential 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 of the SP481E and SP485E 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 receiver for the SP481E and SP485E will
operate up to at least 10Mbps. The receiver for
each of the two 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.
Shutdown Mode
SP481E
The SP481E 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 SP481E into Shutdown
mode. In Shutdown, supply current will drop to
typically 1µA.
ESD TOLERANCE
The SP481E Family 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 dis-
charges 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
May11-2007
SP481E Low Power Half-Duplex RS485 Transceivers
6
© 2007 Sipex Corporation