SP1481E Datasheet, PDF (6/10 Pages) Sipex Corporation – ±15kV Enhanced Low Power Half-Duplex RS-485 Transceivers

DESCRIPTION
The SP1481E and SP1485E are half-duplex
differential transceivers that meet the require-
ments of RS-485 and RS-422.Fabricated
with a Exar proprietary BiCMOS process,
these 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 receiv-
ers to be connected to a data bus, making it
an ideal choice for multi-drop applications.
Since thecabling 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 SP1481E and
SP1485E 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 volt-
age levels.The drivers of the SP1481E, and
SP1485E 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 SP1481E and
SP1485E will operate up to at least
20Mbps.
Receivers
The SP1481E and SP1485E 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 of the
SP1481E and SP1485E 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 dis-
able the receiver.
The receiver for the SP1481E and SP1485E
will operate up to at least 20Mbps.The receiver
for each of thetwo 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
SP1481E
The SP1481E 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 SP1481E into Shut-
down mode.In Shutdown, supply current will
drop to typically 1μA.
ESD Tolerance
The SP1481E Family incorporates rug-
gedized 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
The Human Body Model has been the
generally accepted ESD testing method
for semiconductors. This method is also
specified in MIL-STD-883, Method 3015.7
for ESD testing. The premise of this ESD
test is to simulate the human body’s potential
to store electro-static energy and discharge
it to an integrated circuit.The simulation is
performed by using a test model as shown
in Figure 7. This method will test the IC’s
capability to withstand an ESD transient dur-
ing normal handling such as in manufactur-
ing areas where the ICs tend to be handled
frequently.
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com

SP1481E-1485E_100_061609