Rev. 5/16/03

SP481E Low Power Half-Duplex RS485 Transceivers

© Copyright 2003 Sipex Corporation

6

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 15k

Ω (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 1

µA.

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

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 54

Ω 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.