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Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 50-668-707 • www.exar.com

SP48E,485E_00_2808

The

SP481E and SP485E are half-duplex

differentialtransceiversthatmeettherequire-

ments of RS-485 and RS-422. Fabricated

with an

Exar proprietary BiCMOS process,

this product requires a fraction of the power

of older bipolar designs.

The RS-485 standard is ideal for multi-drop

applicationsandforlong-distanceinterfaces.

RS-485allowsupto32driversand32receiv-

ers 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 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

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 differential outputs, the

drivers can maintain greater than 1.5V volt-

age 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 the DE(pin 3) will tri-state the

driver outputs.

Thetransmittersofthe

SP481EandSP485E

will operate up to at least 10Mbps.

Receivers

The

SP481E and SP485E 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

SP481E and SP485E have a tri-state en-

able 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

driver and receiver must be disabled simul-

taneously. A logic LOW on DE (pin 3) and a

LogicHIGHonRE(pin2)willputthe

SP481E

into Shutdown mode. In Shutdown, supply

current will drop to typically µA.

ESD TOLERANCE

The

SP481E and SP485E 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 discharges and

associated transients. The improved ESD

tolerance is at least ±15kV without damage

or latch-up.

There are different methods of ESD testing

applied:

a) MIL-STD-883, Method 305.7

b) IEC1000-4-2 Air-Discharge

c) IEC000-4-2 Direct Contact

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