SP488A/489ADS/07

SP488A/489A High Speed Quad RS-485/RS-422 Line Receivers

© Copyright 2000 Sipex Corporation

6

Table 2. SP489A Truth Table

DIFFERENTIAL

ENABLES

OUTPUT

A – B

RO

H

H

H

X

H

L

X

L

Hi–Z

FEATURES…

The SP488A and SP489A are low–power quad

differential line receivers meeting RS-485 and

RS-422 serial protocol.

The SP488A and

SP489A feature Sipex's BiCMOS process

allowing low power operational characteristics

of CMOS technology while meeting all of the

demands of the RS-485 and RS-422 serial

protocols over 10Mbps under load in harsh

environments. In fact, the SP488A and SP489A

can transmit signals up to 30Mbps.

The RS-485 standard is ideal for multi-drop

applications and for long-distance communica-

tion. 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.

DIFFERENTIAL

ENABLES

OUTPUT

A – B

EN

EN

RO

V

H

X

H

XL

H

–0.2V < V

H

X

X

XL

X

V

H

X

L

XL

L

X

L

H

Hi–Z

Table 1. SP488A Truth Table

Normally an RS-485 driver will produce no less

than 1.5V before cable attenuation. After cable

loss, the signal may degrade and have an

amplitude of less than 1.0V. The receiver input

sensitivity of the SP488A and SP489A allows

the devices to receive signals as low as 200mV.

The SP488A features active high and active

low common receiver enable controls; the

SP489A provides independent, active high

receiver enable controls for each pair of

receivers. Both feature tri–state outputs and

a -7V to +12V common–mode input range

permitting a

±7V ground difference between

devices on the communications bus. The

SP488A/489A are equipped with a fail–safe

feature which forces a logic high at the

receiver output when the input is left floating.

Both are available in 16-pin plastic DIP and

SOIC packages.