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

SP483_485_0_0627

The

SP483 and SP485 are half-duplex dif-

ferential transceivers that meet the require-

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 +2V) 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

SP483 and SP485

The driver outputs of the

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

acrossthedifferentialoutputs,thedriverscan

maintain greater than .5V voltage levels.

The drivers of the

SP483 and SP485 have

an enable control line which is active HIGH.

A logic HIGH on DE (pin 3) will enable the

differentialdriveroutputs. AlogicLOWonthe

DE(pin 3) will tri-state the driver outputs.

Thetransmittersofthe

SP485willoperateup

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

SP483 and SP485

The

SP483 and SP485 receivers have dif-

ferential 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 +2V

allows for large ground potential differences

between systems. The receivers of the

SP483 and SP485 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

SP485 will operate up

to at least 0Mbps. 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

SP483

The

SP483 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

Logic HIGH on RE (pin 2) will put the

SP483

into Shutdown mode. In Shutdown, supply

current will drop to typically µA.

DESCRIPTION